{"gene":"PF3D7_1408000","run_date":"2026-09-08T14:19:07","timeline":{"discoveries":[{"year":1996,"finding":"Crystal structure of PMII (plasmepsin II) complexed with pepstatin A was determined, revealing the enzyme as an aspartic protease with two different interdomain conformations in the crystal, indicating remarkable interdomain flexibility. The structure was used to design selective low-molecular-weight inhibitors that inhibit both PMII and P. falciparum growth in culture.","method":"X-ray crystallography (crystal structure determination), structure-based inhibitor design, P. falciparum growth inhibition assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation (inhibitor design and parasite growth inhibition), first reported structure of a P. falciparum protein","pmids":["8816746"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1994,"finding":"PMII was expressed recombinantly in E. coli, refolded from inclusion bodies, and shown to be an active aspartic protease that hydrolyzes chromogenic peptide substrates. Despite ~35% identity to human renin, PMII was not significantly inhibited by renin inhibitors.","method":"Recombinant protein expression, refolding, ion-exchange purification, enzymatic activity assay with chromogenic peptide substrates","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro reconstitution of enzymatic activity with substrate hydrolysis assay","pmids":["7925966"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1997,"finding":"PMII is synthesized later in parasite development (trophozoite stage) compared to plasmepsin I (ring stage). Both proplasmepsins are type II integral membrane proteins transported through the secretory pathway before cleavage to soluble form. They are not glycosylated in vivo. Proplasmepsin maturation requires acidic conditions and is inhibited by tripeptide aldehydes but not by canonical aspartic or cysteine protease inhibitors, suggesting maturation is not autocatalytic in vivo and may require an unusual processing enzyme.","method":"Metabolic labeling, pulse-chase biosynthesis, pharmacological inhibition with protease inhibitors, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (pulse-chase, inhibitor profiling, fractionation) in a focused mechanistic study","pmids":["9169469"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1997,"finding":"PMII cleaves hemoglobin and generates discrete peptide fragments in digestive vacuole lysate, acting as an endoproteinase with cleavage sites averaging 8.4 amino acids apart. No free amino acids were detected, supporting a model where small peptides are transported out of the digestive vacuole for further exopeptidase processing in the cytoplasm.","method":"In vitro hemoglobin digestion with digestive vacuole lysate, mass spectrometry identification of cleavage products, colorimetric aminopeptidase assay","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro cleavage assay with mass spectrometry, but PMII activity not separated from other vacuolar enzymes in all experiments","pmids":["9247924"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1999,"finding":"Crystal structure of the proplasmepsin II zymogen was determined. A large N-domain shift relative to the central and C-domains opens the active site cleft, preventing formation of a functional catalytic dyad. The prosegment acts as a 'harness' keeping domains apart rather than occluding a pre-formed active site (a mechanism distinct from gastric aspartic proteinase zymogens). Disruption of key salt bridges at low pH may trigger activation.","method":"X-ray crystallography of proplasmepsin II zymogen","journal":"Nature structural biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of the zymogen with clear mechanistic interpretation of activation mechanism","pmids":["9886289"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1999,"finding":"PMII is active at neutral pH (pH 6.8) on erythrocyte membrane skeleton components: recombinant PMII cleaved spectrin (within the SH3 motif), actin, and protein 4.1 from erythrocyte ghosts. Mass spectrometry identified PMII cleavage sites in the spectrin SH3 motif. Confocal immunofluorescence in schizont-infected erythrocytes localized PMII antibody signal to the periphery of mature parasites, suggesting a role in cytoskeletal remodeling in addition to hemoglobin degradation.","method":"In vitro cleavage of recombinant SH3 motif and native spectrin by recombinant PMII, mass spectrometry of cleavage products, Western blotting with anti-PMII antibodies, confocal immunofluorescence","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vitro substrate cleavage assay with mass spectrometry plus localization; role in cytoskeletal cleavage in vivo not fully established","pmids":["10318841"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1996,"finding":"Kinetic parameters of PMII were established using a synthetic fluorogenic peptide substrate based on the initial hemoglobin cleavage site. Recombinant PMII behaves similarly to the native enzyme kinetically. A polyproline loop swap experiment showed that this loop does not determine substrate specificity in PMII (unlike its role in renin).","method":"Fluorogenic peptide substrate assay, kinetic parameter determination, domain-swap mutagenesis","journal":"Molecular and biochemical parasitology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinetic assays with recombinant and native enzyme, validated by mutagenesis","pmids":["8844673"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2002,"finding":"Genome-wide analysis established that PMII (along with plasmepsin I, IV, and HAP) is expressed during the hemoglobin-degrading intraerythrocytic stage and localizes to the food vacuole, where it functions as an active hemoglobin-degrading protease.","method":"Gene expression analysis, immunolocalization, enzymatic activity assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization and activity data but reported in the context of a genome-wide survey; PMII-specific results confirmed","pmids":["11782538"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2004,"finding":"Targeted gene disruption by double crossover homologous recombination showed that PMII is individually dispensable for parasite viability in culture. Parasites with PMII deletion are viable and morphologically normal but exhibit a longer doubling time in rich medium (decreased productive progeny) and slower growth in amino acid-limited medium, indicating functional redundancy among vacuolar plasmepsins with PMII contributing to optimal growth.","method":"Targeted gene disruption (double crossover homologous recombination), parasite growth assays in normal and amino acid-limited media, protease inhibitor sensitivity assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic knockouts with defined growth phenotypes, multiple nutrient conditions tested","pmids":["15513918"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2004,"finding":"PMII trafficking to the food vacuole was traced using a chromosomally encoded proPMII-GFP chimera in live parasites. proPMII is transported through the secretory system to cytostomal vacuoles and then carried along with hemoglobin substrate to the food vacuole, where it is proteolytically processed to mature PMII. This pathway was established using GFP fluorescence in live cells, immunoelectron microscopy, and pharmacological inhibitors of trafficking and maturation.","method":"Chromosomal proPMII-GFP fusion, live fluorescence microscopy, immunoelectron microscopy, pharmacological inhibitors of trafficking and maturation","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (live imaging, immuno-EM, pharmacological perturbation) all supporting the same trafficking model","pmids":["14709539"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"PMII (and other food vacuole plasmepsins) are activated primarily by the cysteine proteases falcipains, which cleave them from the membrane. If falcipain activity is blocked, PMII can undergo autoprocessing as an alternate activation route, establishing a further level of redundancy between protease families.","method":"Chemical biology (cysteine protease inhibitors), cell biology (fluorescence microscopy of processing), enzymology (in vitro processing assays)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — combination of cell biology, chemical biology, and in vitro enzymology establishing the activation mechanism with alternate pathway characterized","pmids":["18308731"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"Using proPMII-GFP transfectants and quantitative flow cytometry, the digestive vacuole pH was determined to be 5.4–5.5 (the compartment where PMII is active), with no significant difference between chloroquine-sensitive and -resistant strains. Cytostomal vesicles were found not to be measurably acidic, indicating they are not the site of hemoglobin digestion.","method":"proPMII-GFP chimera transfectants, quantitative flow cytometry pH measurement, GFP photobleaching kinetics, LysoSensor Blue accumulation","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple pH measurement methods using PMII-GFP as a vacuolar reporter; mechanistic link to PMII function inferred from compartment pH","pmids":["17696875"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"finding":"PMII is a component of an ~200-kDa protein complex in the food vacuole required for hemoglobin degradation and hemozoin formation. The complex contains falcipain 2/2', plasmepsin II, plasmepsin IV, histo-aspartic protease, and heme detoxification protein, as demonstrated by co-immunoprecipitation followed by mass spectrometry, gel filtration co-elution, glycerol gradient cosedimentation, and in vitro protein interaction analyses.","method":"Co-immunoprecipitation with mass spectrometry, gel filtration chromatography, glycerol gradient cosedimentation, in vitro protein interaction assays, in vitro hemoglobin-to-hemozoin reconstitution assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal biochemical methods (reciprocal Co-IP/MS, gel filtration, gradient sedimentation, in vitro reconstitution) all supporting complex membership","pmids":["23471987"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1997,"finding":"Thermodynamic analysis of pepstatin binding to PMII by isothermal titration calorimetry established the protonation states of the catalytic aspartate residues: Asp34 has a pKa of ~6.5 and Asp214 has a pKa of ~3.0 in the presence of bound ligand, with His164 (pKa ~7.5) also changing protonation on binding. At pH 5.0 (optimum activity), the total charge of the active-site aspartates is -1.","method":"Isothermal titration calorimetry, circular dichroism, thermodynamic proton linkage analysis","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct thermodynamic measurement of protonation states with multiple biophysical methods","pmids":["9405050"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1999,"finding":"Active site specificity of PMII was mapped using chromogenic octapeptide substrates with systematic substitutions, identifying preferred residues at each subsite (optimal substrate: Lys-Pro-Ile-Leu-Phe*Nph-Ala/Glu-Leu-Lys). Site-directed mutagenesis of Met13, Ser77, and Ile287 showed that Met13Glu and Ile287Glu mutations confer ability to cleave substrates containing Lys residues, identifying these residues as determinants of active site specificity.","method":"Chromogenic peptide substrate assays, site-directed mutagenesis of active site residues","journal":"Protein science","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic substrate specificity mapping combined with mutagenesis establishing specific residue contributions to substrate recognition","pmids":["10548045"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2004,"finding":"PMII has distal substrate interactions extending to the P6 position: N-terminal extension of a fluorescence-quenched octapeptide substrate increases maximal velocity, while concentration-dependent substrate inhibition also appears. Site-directed mutagenesis identified PMII residues that interact with N-terminal amino acids of peptide substrates. These same residues influence PMII degradation of hemoglobin. PMII can degrade native hemoglobin (a substrate for PMII but not for the related mammalian enzyme cathepsin E), suggesting PMII may have a hemoglobin denaturase activity.","method":"Fluorescence-quenched peptide substrate kinetics, N-terminal substrate extension assays, site-directed mutagenesis, hemoglobin degradation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic assays with systematic mutagenesis establishing specific residue contributions, replicated with native hemoglobin substrate","pmids":["15574427"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2003,"finding":"Novel crystal structures of uncomplexed PMII (1.9 Å) and PMII in complex with a potent non-peptidic inhibitor (2.7 Å) revealed that the binding cavity is considerably more open than in the pepstatin A complex, accommodating larger heterocyclic groups in P1', P2', and P2 positions. Crystal contacts show extensive interlocking of monomers with >2300 Ų buried at the interface.","method":"X-ray crystallography","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structures of both apo and inhibitor-bound forms, revealing functionally relevant conformational flexibility","pmids":["12614616"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2002,"finding":"Crystal structures of Ser205 mutant PMII in complex with two hydroxypropylamine transition-state mimetic inhibitors (rs367 and rs370) at 1.8 Å revealed key conserved hydrogen bonds between inhibitor and PMII binding-cavity residues including flap residues Val78 and Ser79, catalytic dyad Asp34 and Asp214, and Ser218 and Gly36. Structures showed unexpected conformational variability of the binding cavity.","method":"X-ray crystallography of mutant PMII-inhibitor complexes","journal":"Acta crystallographica. Section D, Biological crystallography","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structures identifying specific catalytic residue interactions with inhibitors","pmids":["12454457"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"X-ray structure of PMII at 1.6 Å with a potent achiral inhibitor revealed an unprecedented binding orientation in which the inhibitor contacts the catalytic aspartates indirectly via the 'catalytic' water. Major side chain rearrangements in the active site open a new pocket, and a second inhibitor molecule was located in the active site.","method":"X-ray crystallography","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure with novel mechanistic insight into indirect catalytic water-mediated binding mode","pmids":["15840589"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1998,"finding":"Recombinant PMII digests fetal hemoglobin (HbF) only half as well as adult hemoglobin A (HbA) in vitro, providing a molecular mechanism for the protection conferred by HbF against malaria: HbF's resistance to PMII digestion slows parasite growth.","method":"In vitro hemoglobin digestion assay with recombinant PMII, comparison of HbF vs HbA substrates","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct in vitro enzymatic assay, single lab, but provides clear mechanistic finding about substrate preference","pmids":["9746793"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"HIV-1 protease inhibitor lopinavir inhibits PMII at an IC50 of 2.7 μM, and all seven tested HIV-1 protease inhibitors inhibit P. falciparum parasite development in culture at pharmacologically relevant concentrations, suggesting PMII as one of their antimalarial targets.","method":"PMII enzyme inhibition assay (IC50 determination), P. falciparum growth inhibition assay","journal":"Antimicrobial agents and chemotherapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct enzyme inhibition assay and parasite growth assay, but causal link between PMII inhibition and parasite killing not fully established","pmids":["15980379"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"PMII interacts with PTEX (Plasmodium translocon of exported proteins) core components, as shown by co-immunoprecipitation. PMII and falcipain 2a were proposed to be translocated via PTEX into the parasitophorous vacuole to reach the cytostome prior to food vacuole entry. Knockdown of PTEX150 perturbed hemoglobin digestion and affected PMII trafficking.","method":"Conditional PTEX150 knockdown, co-immunoprecipitation of PMII with PTEX components, transgenic parasite lines, hemoglobin digestion assays","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and conditional knockdown support PTEX interaction and trafficking role, but mechanistic detail of translocation is inferred rather than directly demonstrated","pmids":["37523385"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Overexpression of PMII and plasmepsin III in the 3D7 genetic background failed to alter P. falciparum sensitivity to artesunate, chloroquine, or piperaquine by dose-response analysis or piperaquine survival assay, indicating that PMII overexpression alone is not sufficient to confer piperaquine resistance.","method":"Transgenic overexpression of PMII/PMIII in 3D7, dose-response drug susceptibility assay, piperaquine survival assay","journal":"International journal for parasitology. Drugs and drug resistance","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic manipulation with defined negative phenotypic outcome; negative result is mechanistically informative","pmids":["30580023"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2025,"finding":"CRISPR-Cas9 knockout of PMII in Cambodian parasites with multiple plasmepsin gene copies increased parasite sensitivity to piperaquine. Parasites with PMII deletions showed slowed hemoglobin digestion. However, protease inhibitors had minimal impact on PPQ susceptibility, and higher plasmepsin copy number parasites did not show significantly increased hemoglobin digestion or different peptide composition or free heme following PPQ treatment compared to wildtype (single copy) parasites.","method":"CRISPR-Cas9 gene knockout of PMII and PMIII, piperaquine susceptibility assays, hemoglobin digestion assays, peptide composition analysis","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean CRISPR knockouts with defined phenotypic readouts; mechanistic basis of PPQ resistance modulation by PMII remains partially unresolved","pmids":["40720544"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"Crystal structures of PMII in complex with HIV-1 protease inhibitors ritonavir and lopinavir were determined. Both drugs interact with PMII via multiple hydrogen bonding and hydrophobic interactions; ritonavir's P4 moiety forms additional interactions compared to lopinavir and exhibits conformational flexibility in a large S4 pocket. Biochemical assays confirmed that ritonavir and lopinavir exhibit the highest inhibition activity against PMII among plasmepsins tested.","method":"X-ray crystallography of PMII-drug complexes, enzyme inhibition assays","journal":"Current research in structural biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structures with biochemical validation in a single focused study","pmids":["38304146"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"Catestatin (a chromogranin A-derived peptide) shows a specific protein-protein interaction with PMII precursor, demonstrated in the presence of parasite-specific lactate dehydrogenase. Catestatin partially inhibits plasmepsin activity in vitro.","method":"Protein-protein interaction assay, enzyme inhibition assay","journal":"Cellular and molecular life sciences","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, interaction assay details limited in abstract; partial inhibition only","pmids":["20043183"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2024,"finding":"Using a genetic cross between a Cambodian multi-drug resistant isolate (KH004, with multiple pm2/3 copies) and a drug-susceptible Malawian parasite (Mal31, single copy pm2/3), inheritance of increased pm2/3 copy number further decreased PPQ susceptibility but did not confer resistance in the absence of additional pfcrt mutations. This epistasis analysis established that PMII copy number variation modulates but does not independently cause piperaquine resistance.","method":"Genetic cross, recovery of 104 recombinant progeny, PPQ survival assay, dose-response area under curve, IC50 determination, competitive fitness assays","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Strong — experimental genetic cross with 104 progeny, multiple PPQ phenotypic assays, robust epistasis analysis","pmids":["38912775"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"PMII (PF3D7_1408000) is an aspartic protease synthesized as a type II integral membrane proenzyme (proplasmepsin II) in the trophozoite stage; the proenzyme is trafficked through the secretory pathway and cytostomal vacuoles—assisted by PTEX—to the food vacuole, where falcipains (with autoprocessing as a backup) cleave it to the soluble, active form that degrades hemoglobin at pH 5.4–5.5, generates peptide intermediates for transport out of the vacuole, and participates in a ~200-kDa multi-protease complex with falcipain-2/2', plasmepsin IV, HAP, and heme detoxification protein; PMII is individually dispensable for parasite viability (due to functional redundancy) but contributes to optimal growth, can also cleave erythrocyte cytoskeletal proteins (spectrin, actin, protein 4.1) at neutral pH, and increased copy number of the pmII/III locus modulates (but does not independently confer) piperaquine resistance in the context of pfcrt mutations."},"narrative":{"mechanistic_narrative":"PMII (PF3D7_1408000) is a food-vacuole aspartic protease of Plasmodium falciparum that initiates hemoglobin catabolism during the intraerythrocytic trophozoite stage [PMID:11782538, PMID:9247924]. It is synthesized as a type II integral membrane proenzyme (proplasmepsin II) later in development than plasmepsin I, transported through the secretory pathway to cytostomal vacuoles and carried with hemoglobin substrate to the acidic (pH 5.4-5.5) food vacuole, where it is cleaved to the soluble mature enzyme [PMID:9169469, PMID:14709539, PMID:17696875]; PTEX core components interact with PMII and are required for its normal trafficking and for hemoglobin digestion [PMID:37523385]. Zymogen activation proceeds primarily through cleavage by falcipain cysteine proteases, with autoprocessing serving as a redundant backup route [PMID:18308731]; structurally, the prosegment holds the N-domain shifted away from the catalytic dyad rather than occluding a preformed active site, so low-pH disruption of salt bridges permits assembly of the functional catalytic-aspartate pair (Asp34/Asp214) [PMID:9886289, PMID:9405050]. As an endoproteinase, PMII cleaves native hemoglobin into discrete peptides for downstream exopeptidase processing outside the vacuole [PMID:9247924, PMID:15574427], with active-site subsite residues (e.g. Met13, Ile287) governing substrate specificity from the S1 pocket out to distal positions [PMID:10548045, PMID:15574427]. In the food vacuole PMII is a member of an ~200-kDa multiprotease complex containing falcipain-2/2', plasmepsin IV, histo-aspartic protease, and heme detoxification protein that couples hemoglobin degradation to hemozoin formation [PMID:23471987]. PMII is individually dispensable for viability owing to redundancy among vacuolar plasmepsins, but its loss lengthens doubling time and impairs growth under amino-acid limitation [PMID:15513918]. Beyond hemoglobin, recombinant PMII cleaves erythrocyte cytoskeletal proteins (spectrin, actin, protein 4.1) at neutral pH and localizes to the periphery of mature parasites [PMID:10318841]. Multiple crystal structures reveal marked interdomain and active-site flexibility that has been exploited for inhibitor design, and HIV-1 protease inhibitors such as lopinavir and ritonavir inhibit PMII and block parasite growth [PMID:8816746, PMID:12614616, PMID:38304146, PMID:15980379]. Increased pm2/3 copy number modulates but does not independently confer piperaquine resistance, which requires additional pfcrt mutations [PMID:38912775, PMID:30580023, PMID:40720544].","teleology":[{"year":1994,"claim":"Establishing that PMII is a genuine catalytically active aspartic protease was the first step, distinguishing it functionally from its closest human relative renin.","evidence":"Recombinant expression in E. coli, refolding, and chromogenic peptide hydrolysis assays","pmids":["7925966"],"confidence":"High","gaps":["Physiological substrate not addressed","In vivo activation and localization unknown at this stage"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1996,"claim":"Solving the pepstatin-bound structure and defining kinetic parameters gave the atomic and catalytic framework needed to design selective inhibitors that also kill parasites, validating PMII as a drug target.","evidence":"X-ray crystallography with pepstatin A, structure-based inhibitor design, fluorogenic substrate kinetics with domain-swap mutagenesis, parasite growth inhibition","pmids":["8816746","8844673"],"confidence":"High","gaps":["Whether inhibitor killing is due specifically to PMII inhibition not established","Interdomain flexibility functional consequences unclear"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1997,"claim":"Biosynthesis, protonation-state, and hemoglobin-cleavage studies together placed PMII in the hemoglobin-degradation pathway and clarified its acidic activity requirements and endoproteinase mode of action.","evidence":"Pulse-chase biosynthesis and inhibitor profiling, isothermal titration calorimetry of pepstatin binding, in vitro hemoglobin digestion with vacuole lysate and mass spectrometry","pmids":["9169469","9405050","9247924"],"confidence":"High","gaps":["Identity of the in vivo maturation enzyme unresolved","PMII-specific hemoglobin cleavage not separated from other vacuolar proteases in all assays"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1998,"claim":"Comparing HbF and HbA digestion linked PMII substrate preference to a host protective phenotype, showing enzyme-level substrate discrimination has physiological consequences.","evidence":"In vitro recombinant PMII digestion of fetal versus adult hemoglobin","pmids":["9746793"],"confidence":"Medium","gaps":["Single-lab in vitro comparison","Contribution relative to other plasmepsins in vivo not addressed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1999,"claim":"The zymogen structure, active-site specificity mapping, and neutral-pH cytoskeletal cleavage collectively defined the activation mechanism, substrate recognition determinants, and a possible second (cytoskeletal) function.","evidence":"X-ray crystallography of proplasmepsin II, chromogenic octapeptide substitution scans with mutagenesis, in vitro cleavage of spectrin/actin/protein 4.1 with mass spectrometry and immunofluorescence","pmids":["9886289","10548045","10318841"],"confidence":"High","gaps":["In vivo relevance of neutral-pH cytoskeletal cleavage not established","Trigger of the pH-dependent domain shift not experimentally isolated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2004,"claim":"Genetic disruption, live-cell trafficking tracing, and extended substrate mapping together established that PMII is dispensable yet growth-promoting, and defined its route to the food vacuole and its distal substrate contacts.","evidence":"Double-crossover gene disruption with growth assays, chromosomal proPMII-GFP with live imaging and immuno-EM, fluorescence-quenched peptide extension kinetics with mutagenesis and native hemoglobin degradation","pmids":["15513918","14709539","15574427"],"confidence":"High","gaps":["Molecular basis of redundancy among plasmepsins not dissected","Proposed hemoglobin denaturase activity mechanism not fully defined"],"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2007,"claim":"Using proPMII-GFP as a reporter fixed the food vacuole pH at 5.4-5.5 and excluded cytostomal vesicles as digestion sites, pinning PMII activity to the acidic terminal compartment.","evidence":"proPMII-GFP transfectants, flow cytometry pH measurement, GFP photobleaching, LysoSensor Blue","pmids":["17696875"],"confidence":"Medium","gaps":["Link from compartment pH to PMII function is inferred","No direct in-compartment activity readout"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"claim":"Identifying falcipains as the primary maturation proteases with autoprocessing as backup explained how the membrane-bound zymogen is converted to soluble enzyme and revealed cross-family redundancy in activation.","evidence":"Cysteine protease inhibitors, fluorescence microscopy of processing, in vitro processing assays","pmids":["18308731"],"confidence":"High","gaps":["Relative in vivo contribution of falcipain cleavage versus autoprocessing under physiological conditions not quantified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"claim":"Demonstrating PMII membership in an ~200-kDa multiprotease complex reframed hemoglobin degradation and hemozoin formation as a coordinated assembly rather than the action of isolated enzymes.","evidence":"Reciprocal Co-IP/MS, gel filtration, glycerol gradient cosedimentation, in vitro hemoglobin-to-hemozoin reconstitution","pmids":["23471987"],"confidence":"High","gaps":["Stoichiometry and PMII-specific interaction surfaces within the complex not defined","Whether complex assembly is required for PMII activity unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"claim":"Later crystal structures with HIV-1 protease inhibitors and copy-number/knockout drug studies refined the inhibitor-binding landscape and clarified PMII's contribution to piperaquine susceptibility as modulatory rather than causal.","evidence":"X-ray crystallography with ritonavir/lopinavir plus enzyme inhibition, genetic cross with 104 progeny and PPQ assays, CRISPR knockouts with hemoglobin digestion analysis, overexpression drug-susceptibility assays","pmids":["38304146","38912775","40720544","30580023","20043183","15980379","12614616","15840589","12454457"],"confidence":"High","gaps":["Mechanistic basis by which pm2/3 copy number modulates PPQ susceptibility not resolved","Interaction with catestatin only weakly characterized (single lab, partial inhibition)"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How PMII's individual dispensability, its role within the multiprotease complex, and its modulation of drug susceptibility integrate at the systems level remains open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["The precise molecular link between pm2/3 copy number and piperaquine resistance in the pfcrt-mutant context is undefined","The in vivo significance of neutral-pH cytoskeletal cleavage is unestablished","The structural basis of PMII's specific contribution to the ~200-kDa complex is unknown"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["~200-kDa food vacuole multiprotease complex (falcipain-2/2', plasmepsin II, plasmepsin IV, histo-aspartic protease, heme detoxification protein) [#12]"],"partners":["FALCIPAINS (ACTIVATING PROTEASES) [#10]","PTEX CORE COMPONENTS (PTEX150) [#21]","FALCIPAIN-2/2', PLASMEPSIN IV, HISTO-ASPARTIC PROTEASE, HEME DETOXIFICATION PROTEIN (COMPLEX MEMBERS) [#12]","CATESTATIN (CHROMOGRANIN A-DERIVED INHIBITORY PEPTIDE, LOW CONFIDENCE) [#25]"],"other_free_text":["Synthesized as a type II integral membrane proenzyme (proplasmepsin II) in the trophozoite stage; matured to soluble active enzyme by falcipain cleavage with autoprocessing backup [#2, #9, #10].","Catalytic aspartate dyad Asp34/Asp214 with defined protonation states; optimal activity at acidic pH (~5.0-5.5) [#13, #11].","Active-site subsite residues Met13, Ser77, Ile287 and distal (up to P6) contacts govern substrate specificity [#14, #15].","Individually dispensable for viability but contributes to optimal growth under nutrient limitation [#8].","Inhibited by HIV-1 protease inhibitors lopinavir and ritonavir; validated small-molecule and non-peptidic inhibitor target with marked active-site conformational flexibility [#0, #16, #18, #20, #24].","Increased pm2/3 copy number modulates but does not independently confer piperaquine resistance, requiring additional pfcrt mutations [#22, #23, #26]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"11782538","id":"PMC_11782538","title":"Four plasmepsins are active in the Plasmodium falciparum food vacuole, including a protease with an active-site histidine.","date":"2002","source":"Proceedings 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crystal, indicating remarkable interdomain flexibility. The structure was used to design selective low-molecular-weight inhibitors that inhibit both PMII and P. falciparum growth in culture.\",\n      \"method\": \"X-ray crystallography (crystal structure determination), structure-based inhibitor design, P. falciparum growth inhibition assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation (inhibitor design and parasite growth inhibition), first reported structure of a P. falciparum protein\",\n      \"pmids\": [\"8816746\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"PMII was expressed recombinantly in E. coli, refolded from inclusion bodies, and shown to be an active aspartic protease that hydrolyzes chromogenic peptide substrates. Despite ~35% identity to human renin, PMII was not significantly inhibited by renin inhibitors.\",\n      \"method\": \"Recombinant protein expression, refolding, ion-exchange purification, enzymatic activity assay with chromogenic peptide substrates\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro reconstitution of enzymatic activity with substrate hydrolysis assay\",\n      \"pmids\": [\"7925966\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"PMII is synthesized later in parasite development (trophozoite stage) compared to plasmepsin I (ring stage). Both proplasmepsins are type II integral membrane proteins transported through the secretory pathway before cleavage to soluble form. They are not glycosylated in vivo. Proplasmepsin maturation requires acidic conditions and is inhibited by tripeptide aldehydes but not by canonical aspartic or cysteine protease inhibitors, suggesting maturation is not autocatalytic in vivo and may require an unusual processing enzyme.\",\n      \"method\": \"Metabolic labeling, pulse-chase biosynthesis, pharmacological inhibition with protease inhibitors, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (pulse-chase, inhibitor profiling, fractionation) in a focused mechanistic study\",\n      \"pmids\": [\"9169469\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"PMII cleaves hemoglobin and generates discrete peptide fragments in digestive vacuole lysate, acting as an endoproteinase with cleavage sites averaging 8.4 amino acids apart. No free amino acids were detected, supporting a model where small peptides are transported out of the digestive vacuole for further exopeptidase processing in the cytoplasm.\",\n      \"method\": \"In vitro hemoglobin digestion with digestive vacuole lysate, mass spectrometry identification of cleavage products, colorimetric aminopeptidase assay\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro cleavage assay with mass spectrometry, but PMII activity not separated from other vacuolar enzymes in all experiments\",\n      \"pmids\": [\"9247924\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Crystal structure of the proplasmepsin II zymogen was determined. A large N-domain shift relative to the central and C-domains opens the active site cleft, preventing formation of a functional catalytic dyad. The prosegment acts as a 'harness' keeping domains apart rather than occluding a pre-formed active site (a mechanism distinct from gastric aspartic proteinase zymogens). Disruption of key salt bridges at low pH may trigger activation.\",\n      \"method\": \"X-ray crystallography of proplasmepsin II zymogen\",\n      \"journal\": \"Nature structural biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of the zymogen with clear mechanistic interpretation of activation mechanism\",\n      \"pmids\": [\"9886289\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PMII is active at neutral pH (pH 6.8) on erythrocyte membrane skeleton components: recombinant PMII cleaved spectrin (within the SH3 motif), actin, and protein 4.1 from erythrocyte ghosts. Mass spectrometry identified PMII cleavage sites in the spectrin SH3 motif. Confocal immunofluorescence in schizont-infected erythrocytes localized PMII antibody signal to the periphery of mature parasites, suggesting a role in cytoskeletal remodeling in addition to hemoglobin degradation.\",\n      \"method\": \"In vitro cleavage of recombinant SH3 motif and native spectrin by recombinant PMII, mass spectrometry of cleavage products, Western blotting with anti-PMII antibodies, confocal immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vitro substrate cleavage assay with mass spectrometry plus localization; role in cytoskeletal cleavage in vivo not fully established\",\n      \"pmids\": [\"10318841\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Kinetic parameters of PMII were established using a synthetic fluorogenic peptide substrate based on the initial hemoglobin cleavage site. Recombinant PMII behaves similarly to the native enzyme kinetically. A polyproline loop swap experiment showed that this loop does not determine substrate specificity in PMII (unlike its role in renin).\",\n      \"method\": \"Fluorogenic peptide substrate assay, kinetic parameter determination, domain-swap mutagenesis\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinetic assays with recombinant and native enzyme, validated by mutagenesis\",\n      \"pmids\": [\"8844673\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Genome-wide analysis established that PMII (along with plasmepsin I, IV, and HAP) is expressed during the hemoglobin-degrading intraerythrocytic stage and localizes to the food vacuole, where it functions as an active hemoglobin-degrading protease.\",\n      \"method\": \"Gene expression analysis, immunolocalization, enzymatic activity assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization and activity data but reported in the context of a genome-wide survey; PMII-specific results confirmed\",\n      \"pmids\": [\"11782538\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Targeted gene disruption by double crossover homologous recombination showed that PMII is individually dispensable for parasite viability in culture. Parasites with PMII deletion are viable and morphologically normal but exhibit a longer doubling time in rich medium (decreased productive progeny) and slower growth in amino acid-limited medium, indicating functional redundancy among vacuolar plasmepsins with PMII contributing to optimal growth.\",\n      \"method\": \"Targeted gene disruption (double crossover homologous recombination), parasite growth assays in normal and amino acid-limited media, protease inhibitor sensitivity assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic knockouts with defined growth phenotypes, multiple nutrient conditions tested\",\n      \"pmids\": [\"15513918\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PMII trafficking to the food vacuole was traced using a chromosomally encoded proPMII-GFP chimera in live parasites. proPMII is transported through the secretory system to cytostomal vacuoles and then carried along with hemoglobin substrate to the food vacuole, where it is proteolytically processed to mature PMII. This pathway was established using GFP fluorescence in live cells, immunoelectron microscopy, and pharmacological inhibitors of trafficking and maturation.\",\n      \"method\": \"Chromosomal proPMII-GFP fusion, live fluorescence microscopy, immunoelectron microscopy, pharmacological inhibitors of trafficking and maturation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (live imaging, immuno-EM, pharmacological perturbation) all supporting the same trafficking model\",\n      \"pmids\": [\"14709539\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PMII (and other food vacuole plasmepsins) are activated primarily by the cysteine proteases falcipains, which cleave them from the membrane. If falcipain activity is blocked, PMII can undergo autoprocessing as an alternate activation route, establishing a further level of redundancy between protease families.\",\n      \"method\": \"Chemical biology (cysteine protease inhibitors), cell biology (fluorescence microscopy of processing), enzymology (in vitro processing assays)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — combination of cell biology, chemical biology, and in vitro enzymology establishing the activation mechanism with alternate pathway characterized\",\n      \"pmids\": [\"18308731\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Using proPMII-GFP transfectants and quantitative flow cytometry, the digestive vacuole pH was determined to be 5.4–5.5 (the compartment where PMII is active), with no significant difference between chloroquine-sensitive and -resistant strains. Cytostomal vesicles were found not to be measurably acidic, indicating they are not the site of hemoglobin digestion.\",\n      \"method\": \"proPMII-GFP chimera transfectants, quantitative flow cytometry pH measurement, GFP photobleaching kinetics, LysoSensor Blue accumulation\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pH measurement methods using PMII-GFP as a vacuolar reporter; mechanistic link to PMII function inferred from compartment pH\",\n      \"pmids\": [\"17696875\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PMII is a component of an ~200-kDa protein complex in the food vacuole required for hemoglobin degradation and hemozoin formation. The complex contains falcipain 2/2', plasmepsin II, plasmepsin IV, histo-aspartic protease, and heme detoxification protein, as demonstrated by co-immunoprecipitation followed by mass spectrometry, gel filtration co-elution, glycerol gradient cosedimentation, and in vitro protein interaction analyses.\",\n      \"method\": \"Co-immunoprecipitation with mass spectrometry, gel filtration chromatography, glycerol gradient cosedimentation, in vitro protein interaction assays, in vitro hemoglobin-to-hemozoin reconstitution assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal biochemical methods (reciprocal Co-IP/MS, gel filtration, gradient sedimentation, in vitro reconstitution) all supporting complex membership\",\n      \"pmids\": [\"23471987\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Thermodynamic analysis of pepstatin binding to PMII by isothermal titration calorimetry established the protonation states of the catalytic aspartate residues: Asp34 has a pKa of ~6.5 and Asp214 has a pKa of ~3.0 in the presence of bound ligand, with His164 (pKa ~7.5) also changing protonation on binding. At pH 5.0 (optimum activity), the total charge of the active-site aspartates is -1.\",\n      \"method\": \"Isothermal titration calorimetry, circular dichroism, thermodynamic proton linkage analysis\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct thermodynamic measurement of protonation states with multiple biophysical methods\",\n      \"pmids\": [\"9405050\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Active site specificity of PMII was mapped using chromogenic octapeptide substrates with systematic substitutions, identifying preferred residues at each subsite (optimal substrate: Lys-Pro-Ile-Leu-Phe*Nph-Ala/Glu-Leu-Lys). Site-directed mutagenesis of Met13, Ser77, and Ile287 showed that Met13Glu and Ile287Glu mutations confer ability to cleave substrates containing Lys residues, identifying these residues as determinants of active site specificity.\",\n      \"method\": \"Chromogenic peptide substrate assays, site-directed mutagenesis of active site residues\",\n      \"journal\": \"Protein science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic substrate specificity mapping combined with mutagenesis establishing specific residue contributions to substrate recognition\",\n      \"pmids\": [\"10548045\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PMII has distal substrate interactions extending to the P6 position: N-terminal extension of a fluorescence-quenched octapeptide substrate increases maximal velocity, while concentration-dependent substrate inhibition also appears. Site-directed mutagenesis identified PMII residues that interact with N-terminal amino acids of peptide substrates. These same residues influence PMII degradation of hemoglobin. PMII can degrade native hemoglobin (a substrate for PMII but not for the related mammalian enzyme cathepsin E), suggesting PMII may have a hemoglobin denaturase activity.\",\n      \"method\": \"Fluorescence-quenched peptide substrate kinetics, N-terminal substrate extension assays, site-directed mutagenesis, hemoglobin degradation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic assays with systematic mutagenesis establishing specific residue contributions, replicated with native hemoglobin substrate\",\n      \"pmids\": [\"15574427\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Novel crystal structures of uncomplexed PMII (1.9 Å) and PMII in complex with a potent non-peptidic inhibitor (2.7 Å) revealed that the binding cavity is considerably more open than in the pepstatin A complex, accommodating larger heterocyclic groups in P1', P2', and P2 positions. Crystal contacts show extensive interlocking of monomers with >2300 Ų buried at the interface.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structures of both apo and inhibitor-bound forms, revealing functionally relevant conformational flexibility\",\n      \"pmids\": [\"12614616\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Crystal structures of Ser205 mutant PMII in complex with two hydroxypropylamine transition-state mimetic inhibitors (rs367 and rs370) at 1.8 Å revealed key conserved hydrogen bonds between inhibitor and PMII binding-cavity residues including flap residues Val78 and Ser79, catalytic dyad Asp34 and Asp214, and Ser218 and Gly36. Structures showed unexpected conformational variability of the binding cavity.\",\n      \"method\": \"X-ray crystallography of mutant PMII-inhibitor complexes\",\n      \"journal\": \"Acta crystallographica. Section D, Biological crystallography\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structures identifying specific catalytic residue interactions with inhibitors\",\n      \"pmids\": [\"12454457\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"X-ray structure of PMII at 1.6 Å with a potent achiral inhibitor revealed an unprecedented binding orientation in which the inhibitor contacts the catalytic aspartates indirectly via the 'catalytic' water. Major side chain rearrangements in the active site open a new pocket, and a second inhibitor molecule was located in the active site.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure with novel mechanistic insight into indirect catalytic water-mediated binding mode\",\n      \"pmids\": [\"15840589\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Recombinant PMII digests fetal hemoglobin (HbF) only half as well as adult hemoglobin A (HbA) in vitro, providing a molecular mechanism for the protection conferred by HbF against malaria: HbF's resistance to PMII digestion slows parasite growth.\",\n      \"method\": \"In vitro hemoglobin digestion assay with recombinant PMII, comparison of HbF vs HbA substrates\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro enzymatic assay, single lab, but provides clear mechanistic finding about substrate preference\",\n      \"pmids\": [\"9746793\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"HIV-1 protease inhibitor lopinavir inhibits PMII at an IC50 of 2.7 μM, and all seven tested HIV-1 protease inhibitors inhibit P. falciparum parasite development in culture at pharmacologically relevant concentrations, suggesting PMII as one of their antimalarial targets.\",\n      \"method\": \"PMII enzyme inhibition assay (IC50 determination), P. falciparum growth inhibition assay\",\n      \"journal\": \"Antimicrobial agents and chemotherapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct enzyme inhibition assay and parasite growth assay, but causal link between PMII inhibition and parasite killing not fully established\",\n      \"pmids\": [\"15980379\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PMII interacts with PTEX (Plasmodium translocon of exported proteins) core components, as shown by co-immunoprecipitation. PMII and falcipain 2a were proposed to be translocated via PTEX into the parasitophorous vacuole to reach the cytostome prior to food vacuole entry. Knockdown of PTEX150 perturbed hemoglobin digestion and affected PMII trafficking.\",\n      \"method\": \"Conditional PTEX150 knockdown, co-immunoprecipitation of PMII with PTEX components, transgenic parasite lines, hemoglobin digestion assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and conditional knockdown support PTEX interaction and trafficking role, but mechanistic detail of translocation is inferred rather than directly demonstrated\",\n      \"pmids\": [\"37523385\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Overexpression of PMII and plasmepsin III in the 3D7 genetic background failed to alter P. falciparum sensitivity to artesunate, chloroquine, or piperaquine by dose-response analysis or piperaquine survival assay, indicating that PMII overexpression alone is not sufficient to confer piperaquine resistance.\",\n      \"method\": \"Transgenic overexpression of PMII/PMIII in 3D7, dose-response drug susceptibility assay, piperaquine survival assay\",\n      \"journal\": \"International journal for parasitology. Drugs and drug resistance\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic manipulation with defined negative phenotypic outcome; negative result is mechanistically informative\",\n      \"pmids\": [\"30580023\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CRISPR-Cas9 knockout of PMII in Cambodian parasites with multiple plasmepsin gene copies increased parasite sensitivity to piperaquine. Parasites with PMII deletions showed slowed hemoglobin digestion. However, protease inhibitors had minimal impact on PPQ susceptibility, and higher plasmepsin copy number parasites did not show significantly increased hemoglobin digestion or different peptide composition or free heme following PPQ treatment compared to wildtype (single copy) parasites.\",\n      \"method\": \"CRISPR-Cas9 gene knockout of PMII and PMIII, piperaquine susceptibility assays, hemoglobin digestion assays, peptide composition analysis\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean CRISPR knockouts with defined phenotypic readouts; mechanistic basis of PPQ resistance modulation by PMII remains partially unresolved\",\n      \"pmids\": [\"40720544\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Crystal structures of PMII in complex with HIV-1 protease inhibitors ritonavir and lopinavir were determined. Both drugs interact with PMII via multiple hydrogen bonding and hydrophobic interactions; ritonavir's P4 moiety forms additional interactions compared to lopinavir and exhibits conformational flexibility in a large S4 pocket. Biochemical assays confirmed that ritonavir and lopinavir exhibit the highest inhibition activity against PMII among plasmepsins tested.\",\n      \"method\": \"X-ray crystallography of PMII-drug complexes, enzyme inhibition assays\",\n      \"journal\": \"Current research in structural biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structures with biochemical validation in a single focused study\",\n      \"pmids\": [\"38304146\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Catestatin (a chromogranin A-derived peptide) shows a specific protein-protein interaction with PMII precursor, demonstrated in the presence of parasite-specific lactate dehydrogenase. Catestatin partially inhibits plasmepsin activity in vitro.\",\n      \"method\": \"Protein-protein interaction assay, enzyme inhibition assay\",\n      \"journal\": \"Cellular and molecular life sciences\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, interaction assay details limited in abstract; partial inhibition only\",\n      \"pmids\": [\"20043183\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Using a genetic cross between a Cambodian multi-drug resistant isolate (KH004, with multiple pm2/3 copies) and a drug-susceptible Malawian parasite (Mal31, single copy pm2/3), inheritance of increased pm2/3 copy number further decreased PPQ susceptibility but did not confer resistance in the absence of additional pfcrt mutations. This epistasis analysis established that PMII copy number variation modulates but does not independently cause piperaquine resistance.\",\n      \"method\": \"Genetic cross, recovery of 104 recombinant progeny, PPQ survival assay, dose-response area under curve, IC50 determination, competitive fitness assays\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — experimental genetic cross with 104 progeny, multiple PPQ phenotypic assays, robust epistasis analysis\",\n      \"pmids\": [\"38912775\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"PMII (PF3D7_1408000) is an aspartic protease synthesized as a type II integral membrane proenzyme (proplasmepsin II) in the trophozoite stage; the proenzyme is trafficked through the secretory pathway and cytostomal vacuoles—assisted by PTEX—to the food vacuole, where falcipains (with autoprocessing as a backup) cleave it to the soluble, active form that degrades hemoglobin at pH 5.4–5.5, generates peptide intermediates for transport out of the vacuole, and participates in a ~200-kDa multi-protease complex with falcipain-2/2', plasmepsin IV, HAP, and heme detoxification protein; PMII is individually dispensable for parasite viability (due to functional redundancy) but contributes to optimal growth, can also cleave erythrocyte cytoskeletal proteins (spectrin, actin, protein 4.1) at neutral pH, and increased copy number of the pmII/III locus modulates (but does not independently confer) piperaquine resistance in the context of pfcrt mutations.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PMII (PF3D7_1408000) is a food-vacuole aspartic protease of Plasmodium falciparum that initiates hemoglobin catabolism during the intraerythrocytic trophozoite stage [#7, #3]. It is synthesized as a type II integral membrane proenzyme (proplasmepsin II) later in development than plasmepsin I, transported through the secretory pathway to cytostomal vacuoles and carried with hemoglobin substrate to the acidic (pH 5.4-5.5) food vacuole, where it is cleaved to the soluble mature enzyme [#2, #9, #11]; PTEX core components interact with PMII and are required for its normal trafficking and for hemoglobin digestion [#21]. Zymogen activation proceeds primarily through cleavage by falcipain cysteine proteases, with autoprocessing serving as a redundant backup route [#10]; structurally, the prosegment holds the N-domain shifted away from the catalytic dyad rather than occluding a preformed active site, so low-pH disruption of salt bridges permits assembly of the functional catalytic-aspartate pair (Asp34/Asp214) [#4, #13]. As an endoproteinase, PMII cleaves native hemoglobin into discrete peptides for downstream exopeptidase processing outside the vacuole [#3, #15], with active-site subsite residues (e.g. Met13, Ile287) governing substrate specificity from the S1 pocket out to distal positions [#14, #15]. In the food vacuole PMII is a member of an ~200-kDa multiprotease complex containing falcipain-2/2', plasmepsin IV, histo-aspartic protease, and heme detoxification protein that couples hemoglobin degradation to hemozoin formation [#12]. PMII is individually dispensable for viability owing to redundancy among vacuolar plasmepsins, but its loss lengthens doubling time and impairs growth under amino-acid limitation [#8]. Beyond hemoglobin, recombinant PMII cleaves erythrocyte cytoskeletal proteins (spectrin, actin, protein 4.1) at neutral pH and localizes to the periphery of mature parasites [#5]. Multiple crystal structures reveal marked interdomain and active-site flexibility that has been exploited for inhibitor design, and HIV-1 protease inhibitors such as lopinavir and ritonavir inhibit PMII and block parasite growth [#0, #16, #24, #20]. Increased pm2/3 copy number modulates but does not independently confer piperaquine resistance, which requires additional pfcrt mutations [#26, #22, #23].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Establishing that PMII is a genuine catalytically active aspartic protease was the first step, distinguishing it functionally from its closest human relative renin.\",\n      \"evidence\": \"Recombinant expression in E. coli, refolding, and chromogenic peptide hydrolysis assays\",\n      \"pmids\": [\"7925966\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrate not addressed\", \"In vivo activation and localization unknown at this stage\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Solving the pepstatin-bound structure and defining kinetic parameters gave the atomic and catalytic framework needed to design selective inhibitors that also kill parasites, validating PMII as a drug target.\",\n      \"evidence\": \"X-ray crystallography with pepstatin A, structure-based inhibitor design, fluorogenic substrate kinetics with domain-swap mutagenesis, parasite growth inhibition\",\n      \"pmids\": [\"8816746\", \"8844673\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether inhibitor killing is due specifically to PMII inhibition not established\", \"Interdomain flexibility functional consequences unclear\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Biosynthesis, protonation-state, and hemoglobin-cleavage studies together placed PMII in the hemoglobin-degradation pathway and clarified its acidic activity requirements and endoproteinase mode of action.\",\n      \"evidence\": \"Pulse-chase biosynthesis and inhibitor profiling, isothermal titration calorimetry of pepstatin binding, in vitro hemoglobin digestion with vacuole lysate and mass spectrometry\",\n      \"pmids\": [\"9169469\", \"9405050\", \"9247924\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the in vivo maturation enzyme unresolved\", \"PMII-specific hemoglobin cleavage not separated from other vacuolar proteases in all assays\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Comparing HbF and HbA digestion linked PMII substrate preference to a host protective phenotype, showing enzyme-level substrate discrimination has physiological consequences.\",\n      \"evidence\": \"In vitro recombinant PMII digestion of fetal versus adult hemoglobin\",\n      \"pmids\": [\"9746793\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab in vitro comparison\", \"Contribution relative to other plasmepsins in vivo not addressed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"The zymogen structure, active-site specificity mapping, and neutral-pH cytoskeletal cleavage collectively defined the activation mechanism, substrate recognition determinants, and a possible second (cytoskeletal) function.\",\n      \"evidence\": \"X-ray crystallography of proplasmepsin II, chromogenic octapeptide substitution scans with mutagenesis, in vitro cleavage of spectrin/actin/protein 4.1 with mass spectrometry and immunofluorescence\",\n      \"pmids\": [\"9886289\", \"10548045\", \"10318841\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of neutral-pH cytoskeletal cleavage not established\", \"Trigger of the pH-dependent domain shift not experimentally isolated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Genetic disruption, live-cell trafficking tracing, and extended substrate mapping together established that PMII is dispensable yet growth-promoting, and defined its route to the food vacuole and its distal substrate contacts.\",\n      \"evidence\": \"Double-crossover gene disruption with growth assays, chromosomal proPMII-GFP with live imaging and immuno-EM, fluorescence-quenched peptide extension kinetics with mutagenesis and native hemoglobin degradation\",\n      \"pmids\": [\"15513918\", \"14709539\", \"15574427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of redundancy among plasmepsins not dissected\", \"Proposed hemoglobin denaturase activity mechanism not fully defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Using proPMII-GFP as a reporter fixed the food vacuole pH at 5.4-5.5 and excluded cytostomal vesicles as digestion sites, pinning PMII activity to the acidic terminal compartment.\",\n      \"evidence\": \"proPMII-GFP transfectants, flow cytometry pH measurement, GFP photobleaching, LysoSensor Blue\",\n      \"pmids\": [\"17696875\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Link from compartment pH to PMII function is inferred\", \"No direct in-compartment activity readout\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identifying falcipains as the primary maturation proteases with autoprocessing as backup explained how the membrane-bound zymogen is converted to soluble enzyme and revealed cross-family redundancy in activation.\",\n      \"evidence\": \"Cysteine protease inhibitors, fluorescence microscopy of processing, in vitro processing assays\",\n      \"pmids\": [\"18308731\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative in vivo contribution of falcipain cleavage versus autoprocessing under physiological conditions not quantified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrating PMII membership in an ~200-kDa multiprotease complex reframed hemoglobin degradation and hemozoin formation as a coordinated assembly rather than the action of isolated enzymes.\",\n      \"evidence\": \"Reciprocal Co-IP/MS, gel filtration, glycerol gradient cosedimentation, in vitro hemoglobin-to-hemozoin reconstitution\",\n      \"pmids\": [\"23471987\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and PMII-specific interaction surfaces within the complex not defined\", \"Whether complex assembly is required for PMII activity unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Later crystal structures with HIV-1 protease inhibitors and copy-number/knockout drug studies refined the inhibitor-binding landscape and clarified PMII's contribution to piperaquine susceptibility as modulatory rather than causal.\",\n      \"evidence\": \"X-ray crystallography with ritonavir/lopinavir plus enzyme inhibition, genetic cross with 104 progeny and PPQ assays, CRISPR knockouts with hemoglobin digestion analysis, overexpression drug-susceptibility assays\",\n      \"pmids\": [\"38304146\", \"38912775\", \"40720544\", \"30580023\", \"20043183\", \"15980379\", \"12614616\", \"15840589\", \"12454457\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic basis by which pm2/3 copy number modulates PPQ susceptibility not resolved\", \"Interaction with catestatin only weakly characterized (single lab, partial inhibition)\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PMII's individual dispensability, its role within the multiprotease complex, and its modulation of drug susceptibility integrate at the systems level remains open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The precise molecular link between pm2/3 copy number and piperaquine resistance in the pfcrt-mutant context is undefined\", \"The in vivo significance of neutral-pH cytoskeletal cleavage is unestablished\", \"The structural basis of PMII's specific contribution to the ~200-kDa complex is unknown\"],\n      \"attribution\": []\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004190\", \"supporting_discovery_ids\": [1, 6, 14, 15]},\n      {\"term_id\": \"GO:0004175\", \"supporting_discovery_ids\": [3, 5, 19]},\n      {\"term_id\": \"GO:0008233\", \"supporting_discovery_ids\": [3, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020020\", \"supporting_discovery_ids\": [7, 9, 11, 12]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0016020\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0044277\", \"supporting_discovery_ids\": [3, 7, 12, 15]},\n      {\"term_id\": \"GO:0006508\", \"supporting_discovery_ids\": [1, 3, 14]}\n    ],\n    \"complexes\": [\"~200-kDa food vacuole multiprotease complex (falcipain-2/2', plasmepsin II, plasmepsin IV, histo-aspartic protease, heme detoxification protein) [#12]\"],\n    \"partners\": [\"Falcipains (activating proteases) [#10]\", \"PTEX core components (PTEX150) [#21]\", \"Falcipain-2/2', plasmepsin IV, histo-aspartic protease, heme detoxification protein (complex members) [#12]\", \"Catestatin (chromogranin A-derived inhibitory peptide, low confidence) [#25]\"],\n    \"other_free_text\": [\n      \"Synthesized as a type II integral membrane proenzyme (proplasmepsin II) in the trophozoite stage; matured to soluble active enzyme by falcipain cleavage with autoprocessing backup [#2, #9, #10].\",\n      \"Catalytic aspartate dyad Asp34/Asp214 with defined protonation states; optimal activity at acidic pH (~5.0-5.5) [#13, #11].\",\n      \"Active-site subsite residues Met13, Ser77, Ile287 and distal (up to P6) contacts govern substrate specificity [#14, #15].\",\n      \"Individually dispensable for viability but contributes to optimal growth under nutrient limitation [#8].\",\n      \"Inhibited by HIV-1 protease inhibitors lopinavir and ritonavir; validated small-molecule and non-peptidic inhibitor target with marked active-site conformational flexibility [#0, #16, #18, #20, #24].\",\n      \"Increased pm2/3 copy number modulates but does not independently confer piperaquine resistance, requiring additional pfcrt mutations [#22, #23, #26].\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1408000","name":null,"product":"plasmepsin II","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"PMII","evaluation":null}