{"gene":"PF3D7_0623200","run_date":"2026-09-08T12:51:26","timeline":{"discoveries":[{"year":2000,"finding":"FNR (plant-type ferredoxin-NADP+ reductase) from Apicomplexan parasites is nuclear-encoded but localizes to the apicoplast, bearing an N-terminal bipartite transit peptide domain. The recombinant protein was obtained in active form, and the system is proposed to supply reduced ferredoxin for biosynthetic processes in the apicoplast.","method":"Cloning, recombinant protein expression, Western blot showing unprocessed and native forms indicative of apicoplast import/processing, phylogenetic analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization evidence (bipartite transit peptide, Western blot processing), recombinant activity confirmed, single lab","pmids":["11056177"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"FNR and ferredoxin of P. falciparum constitute an NADPH-dependent electron transfer chain that serves as the physiological electron donor for LytB (the last enzyme of the DOXP/MEP isoprenoid biosynthesis pathway). LytB and ferredoxin were shown to form a stable protein complex, and LytB was catalytically active only in the presence of the NADPH→FNR→Fd electron transfer system.","method":"In vitro reconstitution of electron transfer pathway, stable complex formation demonstrated between LytB and ferredoxin, enzymatic activity assay","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with defined components, enzymatic activity shown, stable complex detected; independently corroborated by other studies","pmids":["16289098"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"Recombinant P. falciparum FNR transfers electrons selectively to P. falciparum ferredoxin in a reconstituted NADPH-dependent cytochrome c reduction system, demonstrating that an NADPH→FNR→Fd cascade is operative. The crystal structure of P. falciparum ferredoxin (its redox partner) was solved, showing backbone similarity to plant ferredoxins but with unique surface charge distribution.","method":"Recombinant protein production (synthetic genes), NADPH-dependent cytochrome c reduction assay, X-ray crystallography of Fd","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution assay establishing selective electron transfer, single lab but multiple orthogonal methods","pmids":["17251200"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"Crystal structures of P. falciparum FNR were solved in free form (2.4 Å) and in complex with 2'-phospho-AMP (2.7 Å). The structures reveal a covalent dimer stabilized by an intermolecular disulfide bond at Cys99. Binding of 2'-phospho-AMP (mimicking the adenylate moiety of NADP(H)) triggers a helix-coil transition in the NADP-binding domain. NADP+ and 2'-phospho-AMP promote dimer formation in solution, and the isolated dimer is essentially inactive; full activity is recovered upon disulfide reduction.","method":"X-ray crystallography, kinetic characterization, ligand binding studies, solution studies with oxidizing/reducing agents","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures with functional validation, multiple orthogonal methods (crystallography + kinetics + solution studies), single lab","pmids":["17258767"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"NMR chemical shift perturbation mapping and site-directed mutagenesis of ferredoxin identified two acidic regions on P. falciparum Fd (Asp26/Glu29/Glu34 and Asp65/Glu66) as the dominant electrostatic interaction sites with FNR. Glu29 is the single most important residue; mutations in these regions reduced electron transfer activity and affinity for FNR.","method":"NMR chemical shift perturbation, site-directed mutagenesis of Fd, electron transfer activity assay, affinity chromatography","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR mapping plus mutagenesis plus functional assay, multiple orthogonal methods, single lab","pmids":["17938142"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"P. falciparum FNR displays a kcat five-fold lower than typical plastidic FNRs. Rapid kinetics showed that hydride transfer between NADPH and FAD is slower than in homologues, and the FAD semiquinone species is highly destabilized. These two features account for the enzyme's poor catalytic efficiency. Under oxidizing conditions (H2O2), FNR forms an inactive disulfide-stabilized dimer; glutathione and lipoate can reverse this, suggesting redox-regulated quaternary structure as a possible regulatory mechanism in the apicoplast.","method":"Steady-state and rapid-reaction kinetics, redox potential determination, oxidizing/reducing agent treatments","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical characterization with multiple orthogonal methods (rapid kinetics, redox potentials, solution studies), single lab","pmids":["19523113"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"P. falciparum FNR catalyzes single-electron reduction of quinones (redox cycling), contributing to antiplasmodial activity. The presence of aziridinyl groups on quinones does not enhance redox cycling by FNR; instead aziridinyl-quinones likely act as DNA-alkylating agents after two-electron reduction, which can be carried out by single-electron flavoenzymes including FNR under partial anaerobiosis.","method":"In vitro single-electron reduction rate measurements, multiparameter statistical analysis of antiplasmodial activity","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro enzyme kinetics, multiple compound series, single lab","pmids":["19919822"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"FcB1"}]},{"year":2009,"finding":"His286 in the NADP-binding site of P. falciparum FNR plays a dual role: it provides binding energy for NADPH and favors the catalytically competent orientation of the nicotinamide ring for hydride transfer. Replacement with aliphatic residues decreased both NADPH affinity and kcat; replacement with Gln produced a more active enzyme; replacement with Lys destabilized the nicotinamide-isoalloxazine interaction. Lys249 participates in NADPH recognition via interaction with the 2'-phosphate group.","method":"Site-directed mutagenesis, kinetic characterization, crystal structures of mutant-2'-P-AMP complexes","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — active-site mutagenesis combined with crystal structures and kinetics, multiple orthogonal methods, single lab","pmids":["19736991"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"finding":"The conserved Tyr258 hydroxyl group of P. falciparum FNR, which interacts with the 2'-phosphate of NADPH, is the primary determinant of coenzyme specificity. The Y258F mutation selectively decreased kcat for NADPH-dependent reactions ~2-fold (matching the NADH rate), increased Km for NADPH 4-fold, decreased Km for NADH 3-fold, and reduced coenzyme discrimination from 70-fold to 1.5-fold. Rapid kinetics and active-site titrations indicated the effect arises from destabilization of the catalytically competent conformation of bound NADPH.","method":"Site-directed mutagenesis, steady-state kinetics, rapid-reaction kinetics, active-site titrations, anaerobic photoreduction","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis with multiple orthogonal functional assays establishing mechanism, single lab but rigorous","pmids":["22519987"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Basic amino acid residues on the FAD-binding face of P. falciparum FNR, including residues within a Plasmodium-specific insertion region, are important for interaction with P. falciparum ferredoxin. Comprehensive substitution to acidic residues showed that these basic residues are Plasmodium-specific (not conserved in plants/cyanobacteria), explaining the higher affinity and specificity of PfFd:PfFNR interaction compared to plant systems.","method":"Site-directed mutagenesis of FNR, kinetic analysis of electron transfer, affinity chromatography to immobilized Fd, thermodynamic binding measurements (ITC or equivalent)","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — comprehensive mutagenesis with kinetic, physical binding, and thermodynamic analyses, multiple orthogonal methods, single lab","pmids":["29688515"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"P. falciparum FNR catalyzes single-electron reduction of quinones, nitroaromatic compounds, and aromatic N-oxides via a ping-pong mechanism. Reactivity of all compound classes increases with their single-electron reduction midpoint potential (E17). For quinones, oxidation of FADH• to FAD is the possible rate-limiting step during FAD reoxidation. Ferredoxin stimulates the quinone- and nitro-reductase reactions of FNR by providing an additional reduction pathway via reduced Fd.","method":"In vitro kinetic study of single-electron reduction, ping-pong mechanism analysis, electron transfer distance calculations","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro mechanistic enzyme kinetics with mechanistic analysis, single lab","pmids":["32370303"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"P. falciparum FNR catalyzes redox cycling of the antimalarial compound plasmodione (PD) in the presence of NADPH and oxygen, generating both key metabolites PD-bzol (benzylic alcohol) and PDO (3-benzoylmenadione) via a semiquinone radical intermediate. This FNR-mediated redox cycling generates reactive oxygen species (ROS) in the apicoplast, as demonstrated using a genetically encoded glutathione redox sensor in live parasites.","method":"In vitro enzyme redox cycling assay, LC-MS metabolite detection, live parasite imaging with genetically encoded redox sensor (hGrx1-roGFP2) in transgenic 3D7 P. falciparum","journal":"ACS infectious diseases","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution plus live parasite validation with orthogonal methods, single lab","pmids":["33855850"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2021,"finding":"Three chemically reactive residues are important for P. falciparum FNR activity: Cys99 (active-site, responsible for hydride transfer), Cys284 (whose oxidation leads to inactive dimer), and His286 (NADPH binding). Both cysteines are promising targets for covalent inhibition, as shown using residue-specific chemical reagents.","method":"Site-directed mutagenesis, residue-specific chemical modification, enzymatic activity assays","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — mechanistic residue identification via chemical modification and mutagenesis, single lab, abstract-level detail","pmids":["34509083"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"Genetic deletion of FNR in P. falciparum (using an apicoplast metabolic bypass line) demonstrated that FNR is essential for blood-stage parasite survival but is not required for apicoplast maintenance. The Fd/FNR system provides reducing power to certain downstream iron-sulfur cluster proteins that are individually essential for parasite survival.","method":"Genetic deletion (conditional KO in PfMev apicoplast bypass line), growth/viability assays, double deletion epistasis with FeS transfer proteins SufA and NfuApi","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic deletion with defined phenotypic readout (essentiality), apicoplast bypass system controls, epistasis analysis, replicated across multiple gene deletions","pmids":["35164549"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"P. falciparum FNR (ptFNR) can functionally replace the endogenous E. coli flavodoxin reductase in an E. coli complementation system, where bacterial growth depends on ptFd, ptFNR, and IspH from P. falciparum reconstituting the last step of the MEP isoprenoid biosynthesis pathway. This validated an in situ screening platform for MEP pathway inhibitors and functional mutations.","method":"E. coli complementation (genetic reconstitution), bacterial growth assays, LC-MS metabolite analysis, validation in conditional T. gondii Fd KO strain","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — functional reconstitution in heterologous system with growth readout and metabolomic validation, confirmed in parasites","pmids":["40967433"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"P. falciparum FNR (PF3D7_0623200) is a FAD-containing, apicoplast-localized, plant-type NADPH-dependent oxidoreductase that is essential for blood-stage parasite survival; it transfers electrons from NADPH via FAD to ferredoxin (which then reduces downstream iron-sulfur cluster enzymes including LytB of the MEP isoprenoid pathway), forms an inactive disulfide-stabilized dimer at Cys284/Cys99 under oxidizing conditions, uses Tyr258 and His286/Lys249 for NADPH specificity and hydride transfer, and also catalyzes single-electron reduction of redox-cycling xenobiotics (quinones, nitroaromatics, aromatic N-oxides) via a ping-pong mechanism."},"narrative":{"mechanistic_narrative":"PF3D7_0623200 (FNR) is a nuclear-encoded, plant-type ferredoxin-NADP+ reductase that is targeted to the apicoplast via an N-terminal bipartite transit peptide and supplies reducing power for apicoplast biosynthesis [PMID:11056177]. It initiates an NADPH→FNR→ferredoxin electron transfer cascade in which FNR selectively reduces P. falciparum ferredoxin, which in turn delivers electrons to downstream iron-sulfur cluster enzymes; reconstitution showed this system is the physiological electron donor required for activity of LytB/IspH, the terminal enzyme of the DOXP/MEP isoprenoid pathway [PMID:16289098, PMID:17251200, PMID:40967433]. Genetic deletion in an apicoplast metabolic bypass line established that FNR is essential for blood-stage survival by feeding reducing power to individually essential Fe-S cluster proteins, while being dispensable for apicoplast maintenance itself [PMID:35164549]. Structurally, FNR forms a covalent dimer stabilized by an intermolecular disulfide involving Cys99/Cys284; this dimer is essentially inactive and forms under oxidizing conditions (H2O2), but is reversed by disulfide reduction (glutathione, lipoate), pointing to redox-regulated quaternary structure [PMID:17258767, PMID:19523113, PMID:34509083]. Coenzyme specificity and hydride transfer depend on defined active-site residues: Tyr258 is the primary determinant of NADPH over NADH selectivity, His286 provides binding energy and orients the nicotinamide ring for hydride transfer, and Lys249 recognizes the 2'-phosphate of NADPH [PMID:19736991, PMID:22519987]. Basic residues on the FAD-binding face, including a Plasmodium-specific insertion, engage acidic patches on ferredoxin (notably Glu29) to confer the high-affinity, species-specific Fd:FNR interaction [PMID:17938142, PMID:29688515]. Beyond its physiological cascade, FNR catalyzes single-electron reduction of redox-cycling xenobiotics—quinones, nitroaromatics, and aromatic N-oxides—via a ping-pong mechanism, generating semiquinone radicals and apicoplast ROS, a property exploited by the antimalarial plasmodione [PMID:19919822, PMID:32370303, PMID:33855850].","teleology":[{"year":2000,"claim":"Established that FNR is a nuclear-encoded plant-type reductase trafficked to the apicoplast, defining where in the parasite its redox chemistry operates.","evidence":"Cloning, recombinant expression, and Western blot showing transit-peptide processing plus phylogenetic analysis","pmids":["11056177"],"confidence":"Medium","gaps":["Did not identify the physiological electron acceptor or downstream pathway","Import mechanism inferred from processing, not directly traced"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"claim":"Answered what FNR's reducing power is used for by placing it at the head of an NADPH→FNR→Fd chain that drives the terminal MEP isoprenoid enzyme LytB.","evidence":"In vitro reconstitution with defined components and demonstration of a stable LytB-ferredoxin complex","pmids":["16289098"],"confidence":"High","gaps":["Physiological essentiality not yet demonstrated in parasites","Kinetic parameters of the full cascade not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"claim":"Confirmed the selective electron flow from FNR to its cognate ferredoxin and provided structural context for the redox partner.","evidence":"Reconstituted NADPH-dependent cytochrome c reduction assay and X-ray structure of P. falciparum ferredoxin","pmids":["17251200"],"confidence":"High","gaps":["Interface residues on FNR not yet mapped","FNR structure not solved in this study"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"claim":"Revealed the structural basis of FNR's redox-sensitive quaternary regulation—a disulfide-linked, inactive dimer whose formation is coupled to NADP(H) adenylate binding.","evidence":"Crystal structures of free and 2'-phospho-AMP-bound FNR with kinetic and solution redox studies","pmids":["17258767"],"confidence":"High","gaps":["In vivo relevance of dimerization not established","Cys284 contribution not yet distinguished"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"claim":"Defined the electrostatic docking sites on ferredoxin, showing Glu29 as the dominant residue governing the Fd:FNR interaction.","evidence":"NMR chemical shift perturbation, Fd mutagenesis, and electron transfer/affinity assays","pmids":["17938142"],"confidence":"High","gaps":["Complementary interface residues on FNR not identified in this work","No co-crystal of the complex"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"claim":"Explained the enzyme's unusually low catalytic efficiency and tied its inactivation to oxidative disulfide dimer formation reversible by cellular thiols.","evidence":"Steady-state/rapid-reaction kinetics, redox potential determination, and oxidizing/reducing treatments","pmids":["19523113"],"confidence":"High","gaps":["Whether redox regulation operates in vivo not shown","Biological trigger for oxidation not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"claim":"Dissected the dual role of His286 and the role of Lys249 in NADPH recognition and productive hydride-transfer geometry.","evidence":"Site-directed mutagenesis with kinetics and mutant 2'-P-AMP co-crystal structures","pmids":["19736991"],"confidence":"High","gaps":["Effect on ferredoxin reduction in the full cascade not measured","Contribution to coenzyme discrimination not isolated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"claim":"Showed FNR can perform single-electron quinone reduction, framing it as a mediator of antiplasmodial redox-cycling drug chemistry.","evidence":"In vitro single-electron reduction rate measurements with statistical analysis of antiplasmodial activity","pmids":["19919822"],"confidence":"Medium","gaps":["Cellular relevance of quinone reduction not demonstrated in parasites here","Aziridinyl-quinone two-electron pathway inferred, not directly resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":"FcB1"}]},{"year":2012,"claim":"Identified Tyr258 as the principal determinant of NADPH-over-NADH specificity, acting by stabilizing the catalytically competent coenzyme conformation.","evidence":"Y258F mutagenesis with steady-state and rapid kinetics, active-site titrations, and anaerobic photoreduction","pmids":["22519987"],"confidence":"High","gaps":["Impact on physiological Fd reduction rate not quantified","No structure of the Y258F mutant"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"Mapped the complementary FNR interface, showing Plasmodium-specific basic residues on the FAD-binding face drive the high-affinity, species-specific ferredoxin interaction.","evidence":"Comprehensive FNR mutagenesis with kinetic, affinity, and thermodynamic binding analyses","pmids":["29688515"],"confidence":"High","gaps":["No experimental structure of the Fd:FNR complex","Whether this specificity can be exploited for inhibition untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"Generalized FNR's xenobiotic-reducing activity to quinones, nitroaromatics, and aromatic N-oxides via a ping-pong mechanism, with ferredoxin providing an additional reduction route.","evidence":"In vitro kinetic analysis of single-electron reduction and electron-transfer distance calculations","pmids":["32370303"],"confidence":"Medium","gaps":["In vivo contribution to drug activation not addressed here","Rate-limiting FAD reoxidation step only partially resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"claim":"Demonstrated in live parasites that FNR-driven redox cycling of the antimalarial plasmodione generates apicoplast ROS, linking its enzymology to a drug mechanism of action.","evidence":"In vitro redox cycling with LC-MS metabolite detection and live-parasite imaging with an hGrx1-roGFP2 redox sensor in transgenic 3D7","pmids":["33855850"],"confidence":"High","gaps":["Relative contribution of FNR versus other flavoenzymes in cells not quantified","Downstream ROS targets not identified"],"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2021,"claim":"Nominated Cys99, Cys284, and His286 as chemically reactive, functionally critical residues and candidate covalent-inhibition sites.","evidence":"Site-directed mutagenesis with residue-specific chemical modification and activity assays","pmids":["34509083"],"confidence":"Medium","gaps":["No inhibitor with parasite activity demonstrated","Abstract-level mechanistic detail; selectivity over host reductases untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"claim":"Provided direct genetic proof that FNR is essential for blood-stage survival through supply of reducing power to essential Fe-S cluster proteins, while being dispensable for apicoplast maintenance.","evidence":"Conditional deletion in the PfMev apicoplast metabolic bypass line with growth assays and epistasis against SufA and NfuApi","pmids":["35164549"],"confidence":"High","gaps":["The specific essential Fe-S enzymes downstream not fully enumerated","Non-MEP essential functions not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"claim":"Established a heterologous reconstitution platform in which FNR, ferredoxin, and IspH from P. falciparum functionally replace E. coli flavodoxin reductase, enabling in situ MEP-pathway inhibitor screening.","evidence":"E. coli complementation with growth and LC-MS readouts, validated in a conditional T. gondii Fd KO strain","pmids":["40967433"],"confidence":"High","gaps":["Not a native parasite context for kinetics","Screening hits against FNR itself not reported"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How FNR's redox-regulated dimerization and xenobiotic single-electron chemistry are controlled and exploited in vivo, and whether its species-specific ferredoxin interface can be pharmacologically targeted, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experimental structure of the Fd:FNR complex","In vivo trigger and physiological role of the inactive disulfide dimer not established","No validated FNR-selective inhibitor with parasite efficacy"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Redox-sensitive covalent FNR homodimer stabilized by an intermolecular disulfide (Cys99/Cys284), catalytically inactive and reversed by thiol reduction [#3, #5, #12]","FNR functions with ferredoxin as an NADPH-dependent electron transfer pair; ferredoxin further forms a stable complex with LytB/IspH [#1, #2]"],"partners":["P. FALCIPARUM FERREDOXIN (FD) — COGNATE ELECTRON ACCEPTOR VIA ACIDIC PATCHES INCLUDING GLU29 AND FNR BASIC FAD-FACE RESIDUES [#2, #4, #9]","LYTB/ISPH (TERMINAL MEP PATHWAY ENZYME) — DOWNSTREAM ACCEPTOR OF THE FNR→FD CASCADE [#1, #14]","DOWNSTREAM ESSENTIAL FE-S CLUSTER PROTEINS (FUNCTIONAL EPISTASIS WITH SUFA AND NFUAPI) [#13]"],"other_free_text":["Tyr258 is the primary determinant of NADPH over NADH coenzyme specificity [#8]","His286 provides NADPH binding energy and orients the nicotinamide ring for hydride transfer; Lys249 recognizes the NADPH 2'-phosphate [#7]","Exhibits low catalytic efficiency due to slow hydride transfer and a destabilized FAD semiquinone [#5]","Catalyzes single-electron reduction of quinones, nitroaromatics, and aromatic N-oxides by a ping-pong mechanism; ferredoxin stimulates these reactions [#6, #10]","Mediates redox cycling of the antimalarial plasmodione, generating apicoplast ROS in live parasites [#11]","Essential for blood-stage survival but dispensable for apicoplast maintenance [#13]","Functionally reconstitutable in E. coli as part of a P. falciparum Fd/FNR/IspH MEP module [#14]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"18307973","id":"PMC_18307973","title":"Structural and functional diversity of ferredoxin-NADP(+) reductases.","date":"2008","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/18307973","citation_count":127,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"11056177","id":"PMC_11056177","title":"Apicomplexan parasites possess distinct nuclear-encoded, but apicoplast-localized, plant-type ferredoxin-NADP+ reductase and ferredoxin.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11056177","citation_count":87,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16289098","id":"PMC_16289098","title":"Reconstitution of an apicoplast-localised electron transfer pathway involved in the isoprenoid biosynthesis of Plasmodium falciparum.","date":"2005","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/16289098","citation_count":72,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16178751","id":"PMC_16178751","title":"The plant-type ferredoxin-NADP+ reductase/ferredoxin redox system as a possible drug target against apicomplexan human parasites.","date":"2005","source":"Current pharmaceutical design","url":"https://pubmed.ncbi.nlm.nih.gov/16178751","citation_count":55,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17258767","id":"PMC_17258767","title":"Ferredoxin-NADP+ reductase from Plasmodium falciparum undergoes NADP+-dependent dimerization and inactivation: functional and crystallographic analysis.","date":"2007","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/17258767","citation_count":42,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19523113","id":"PMC_19523113","title":"The ferredoxin-NADP+ reductase/ferredoxin electron transfer system of Plasmodium falciparum.","date":"2009","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/19523113","citation_count":31,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17251200","id":"PMC_17251200","title":"Cloning and characterization of ferredoxin and ferredoxin-NADP+ reductase from human malaria parasite.","date":"2007","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17251200","citation_count":29,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25532844","id":"PMC_25532844","title":"Design and synthesis of chalcone derivatives as inhibitors of the ferredoxin - ferredoxin-NADP+ reductase interaction of Plasmodium falciparum: pursuing new antimalarial agents.","date":"2014","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/25532844","citation_count":23,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35164549","id":"PMC_35164549","title":"Roles of Ferredoxin-Dependent Proteins in the Apicoplast of Plasmodium falciparum Parasites.","date":"2022","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/35164549","citation_count":21,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19919822","id":"PMC_19919822","title":"Antiplasmodial activity of quinones: roles of aziridinyl substituents and the inhibition of Plasmodium falciparum glutathione reductase.","date":"2009","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/19919822","citation_count":21,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32370303","id":"PMC_32370303","title":"Reactions of Plasmodium falciparum Ferredoxin:NADP+ Oxidoreductase with Redox Cycling Xenobiotics: A Mechanistic Study.","date":"2020","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/32370303","citation_count":19,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17938142","id":"PMC_17938142","title":"Molecular interaction of ferredoxin and ferredoxin-NADP+ reductase from human malaria parasite.","date":"2007","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17938142","citation_count":19,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31835450","id":"PMC_31835450","title":"Antiplasmodial Activity of Nitroaromatic Compounds: Correlation with Their Reduction Potential and Inhibitory Action on Plasmodium falciparum Glutathione Reductase.","date":"2019","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/31835450","citation_count":17,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22519987","id":"PMC_22519987","title":"A single tyrosine hydroxyl group almost entirely controls the NADPH specificity of Plasmodium falciparum ferredoxin-NADP+ reductase.","date":"2012","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22519987","citation_count":14,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"29688515","id":"PMC_29688515","title":"Plasmodium-specific basic amino acid residues important for the interaction with ferredoxin on the surface of ferredoxin-NADP+ reductase.","date":"2018","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/29688515","citation_count":11,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19736991","id":"PMC_19736991","title":"Plasmodium falciparum ferredoxin-NADP+ reductase His286 plays a dual role in NADP(H) binding and catalysis.","date":"2009","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19736991","citation_count":10,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33855850","id":"PMC_33855850","title":"Plasmodium falciparum Ferredoxin-NADP+ Reductase-Catalyzed Redox Cycling of Plasmodione Generates Both Predicted Key Drug Metabolites: Implication for Antimalarial Drug Development.","date":"2021","source":"ACS infectious diseases","url":"https://pubmed.ncbi.nlm.nih.gov/33855850","citation_count":10,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"34415329","id":"PMC_34415329","title":"Functional analyses of plasmodium ferredoxin Asp97Tyr mutant related to artemisinin resistance of human malaria parasites.","date":"2021","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/34415329","citation_count":9,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32470136","id":"PMC_32470136","title":"C-terminal aromatic residue of Plasmodium ferredoxin important for the interaction with ferredoxin: NADP(H) oxidoreductase: possible involvement for artemisinin resistance of human malaria parasites.","date":"2020","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/32470136","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33228195","id":"PMC_33228195","title":"Aerobic Cytotoxicity of Aromatic N-Oxides: The Role of NAD(P)H:Quinone Oxidoreductase (NQO1).","date":"2020","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33228195","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30225138","id":"PMC_30225138","title":"Inhibitory Activity and Docking Analysis of Antimalarial Agents from Stemona sp. toward Ferredoxin-NADP+ Reductase from Malaria Parasites.","date":"2018","source":"Journal of parasitology research","url":"https://pubmed.ncbi.nlm.nih.gov/30225138","citation_count":6,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37131988","id":"PMC_37131988","title":"Antagonistic antimalarial properties of a methoxyamino chalcone derivative and 3-hydroxypyridinones in combination with dihydroartemisinin against Plasmodium falciparum.","date":"2023","source":"PeerJ","url":"https://pubmed.ncbi.nlm.nih.gov/37131988","citation_count":4,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FNR","ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"40480411","id":"PMC_40480411","title":"Rational synthesis, activity and mechanism insights of a new aminoquinoline salt against malaria parasites: in vitro and in vivo approaches.","date":"2025","source":"Chemico-biological interactions","url":"https://pubmed.ncbi.nlm.nih.gov/40480411","citation_count":4,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"34509083","id":"PMC_34509083","title":"Covalent inhibition of P. falciparum ferredoxin-NADP+ reductase: Exploring alternative strategies for the development of new antimalarial drugs.","date":"2021","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/34509083","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"40967433","id":"PMC_40967433","title":"Reconstituted ferredoxin-MEP pathway of Apicomplexa in Escherichiacoli as an in situ screening platform for inhibitors and essential enzyme mutations.","date":"2025","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/40967433","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ferredoxin--NADP reductase","NADP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16252,"output_tokens":4442,"usd":0.057693,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10881,"output_tokens":5622,"usd":0.097477,"stage2_stop_reason":"end_turn"},"total_usd":0.15517,"stage1_batch_id":"msgbatch_01DisAaTypwmC8QwdMBuePHo","stage2_batch_id":"msgbatch_0184zxZTqxiEfdYYfPMfkqjb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"FNR (plant-type ferredoxin-NADP+ reductase) from Apicomplexan parasites is nuclear-encoded but localizes to the apicoplast, bearing an N-terminal bipartite transit peptide domain. The recombinant protein was obtained in active form, and the system is proposed to supply reduced ferredoxin for biosynthetic processes in the apicoplast.\",\n      \"method\": \"Cloning, recombinant protein expression, Western blot showing unprocessed and native forms indicative of apicoplast import/processing, phylogenetic analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization evidence (bipartite transit peptide, Western blot processing), recombinant activity confirmed, single lab\",\n      \"pmids\": [\"11056177\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FNR and ferredoxin of P. falciparum constitute an NADPH-dependent electron transfer chain that serves as the physiological electron donor for LytB (the last enzyme of the DOXP/MEP isoprenoid biosynthesis pathway). LytB and ferredoxin were shown to form a stable protein complex, and LytB was catalytically active only in the presence of the NADPH→FNR→Fd electron transfer system.\",\n      \"method\": \"In vitro reconstitution of electron transfer pathway, stable complex formation demonstrated between LytB and ferredoxin, enzymatic activity assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with defined components, enzymatic activity shown, stable complex detected; independently corroborated by other studies\",\n      \"pmids\": [\"16289098\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Recombinant P. falciparum FNR transfers electrons selectively to P. falciparum ferredoxin in a reconstituted NADPH-dependent cytochrome c reduction system, demonstrating that an NADPH→FNR→Fd cascade is operative. The crystal structure of P. falciparum ferredoxin (its redox partner) was solved, showing backbone similarity to plant ferredoxins but with unique surface charge distribution.\",\n      \"method\": \"Recombinant protein production (synthetic genes), NADPH-dependent cytochrome c reduction assay, X-ray crystallography of Fd\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution assay establishing selective electron transfer, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"17251200\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Crystal structures of P. falciparum FNR were solved in free form (2.4 Å) and in complex with 2'-phospho-AMP (2.7 Å). The structures reveal a covalent dimer stabilized by an intermolecular disulfide bond at Cys99. Binding of 2'-phospho-AMP (mimicking the adenylate moiety of NADP(H)) triggers a helix-coil transition in the NADP-binding domain. NADP+ and 2'-phospho-AMP promote dimer formation in solution, and the isolated dimer is essentially inactive; full activity is recovered upon disulfide reduction.\",\n      \"method\": \"X-ray crystallography, kinetic characterization, ligand binding studies, solution studies with oxidizing/reducing agents\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures with functional validation, multiple orthogonal methods (crystallography + kinetics + solution studies), single lab\",\n      \"pmids\": [\"17258767\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"NMR chemical shift perturbation mapping and site-directed mutagenesis of ferredoxin identified two acidic regions on P. falciparum Fd (Asp26/Glu29/Glu34 and Asp65/Glu66) as the dominant electrostatic interaction sites with FNR. Glu29 is the single most important residue; mutations in these regions reduced electron transfer activity and affinity for FNR.\",\n      \"method\": \"NMR chemical shift perturbation, site-directed mutagenesis of Fd, electron transfer activity assay, affinity chromatography\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR mapping plus mutagenesis plus functional assay, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"17938142\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"P. falciparum FNR displays a kcat five-fold lower than typical plastidic FNRs. Rapid kinetics showed that hydride transfer between NADPH and FAD is slower than in homologues, and the FAD semiquinone species is highly destabilized. These two features account for the enzyme's poor catalytic efficiency. Under oxidizing conditions (H2O2), FNR forms an inactive disulfide-stabilized dimer; glutathione and lipoate can reverse this, suggesting redox-regulated quaternary structure as a possible regulatory mechanism in the apicoplast.\",\n      \"method\": \"Steady-state and rapid-reaction kinetics, redox potential determination, oxidizing/reducing agent treatments\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical characterization with multiple orthogonal methods (rapid kinetics, redox potentials, solution studies), single lab\",\n      \"pmids\": [\"19523113\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"P. falciparum FNR catalyzes single-electron reduction of quinones (redox cycling), contributing to antiplasmodial activity. The presence of aziridinyl groups on quinones does not enhance redox cycling by FNR; instead aziridinyl-quinones likely act as DNA-alkylating agents after two-electron reduction, which can be carried out by single-electron flavoenzymes including FNR under partial anaerobiosis.\",\n      \"method\": \"In vitro single-electron reduction rate measurements, multiparameter statistical analysis of antiplasmodial activity\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro enzyme kinetics, multiple compound series, single lab\",\n      \"pmids\": [\"19919822\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"FcB1\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"His286 in the NADP-binding site of P. falciparum FNR plays a dual role: it provides binding energy for NADPH and favors the catalytically competent orientation of the nicotinamide ring for hydride transfer. Replacement with aliphatic residues decreased both NADPH affinity and kcat; replacement with Gln produced a more active enzyme; replacement with Lys destabilized the nicotinamide-isoalloxazine interaction. Lys249 participates in NADPH recognition via interaction with the 2'-phosphate group.\",\n      \"method\": \"Site-directed mutagenesis, kinetic characterization, crystal structures of mutant-2'-P-AMP complexes\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — active-site mutagenesis combined with crystal structures and kinetics, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"19736991\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The conserved Tyr258 hydroxyl group of P. falciparum FNR, which interacts with the 2'-phosphate of NADPH, is the primary determinant of coenzyme specificity. The Y258F mutation selectively decreased kcat for NADPH-dependent reactions ~2-fold (matching the NADH rate), increased Km for NADPH 4-fold, decreased Km for NADH 3-fold, and reduced coenzyme discrimination from 70-fold to 1.5-fold. Rapid kinetics and active-site titrations indicated the effect arises from destabilization of the catalytically competent conformation of bound NADPH.\",\n      \"method\": \"Site-directed mutagenesis, steady-state kinetics, rapid-reaction kinetics, active-site titrations, anaerobic photoreduction\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis with multiple orthogonal functional assays establishing mechanism, single lab but rigorous\",\n      \"pmids\": [\"22519987\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Basic amino acid residues on the FAD-binding face of P. falciparum FNR, including residues within a Plasmodium-specific insertion region, are important for interaction with P. falciparum ferredoxin. Comprehensive substitution to acidic residues showed that these basic residues are Plasmodium-specific (not conserved in plants/cyanobacteria), explaining the higher affinity and specificity of PfFd:PfFNR interaction compared to plant systems.\",\n      \"method\": \"Site-directed mutagenesis of FNR, kinetic analysis of electron transfer, affinity chromatography to immobilized Fd, thermodynamic binding measurements (ITC or equivalent)\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — comprehensive mutagenesis with kinetic, physical binding, and thermodynamic analyses, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"29688515\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"P. falciparum FNR catalyzes single-electron reduction of quinones, nitroaromatic compounds, and aromatic N-oxides via a ping-pong mechanism. Reactivity of all compound classes increases with their single-electron reduction midpoint potential (E17). For quinones, oxidation of FADH• to FAD is the possible rate-limiting step during FAD reoxidation. Ferredoxin stimulates the quinone- and nitro-reductase reactions of FNR by providing an additional reduction pathway via reduced Fd.\",\n      \"method\": \"In vitro kinetic study of single-electron reduction, ping-pong mechanism analysis, electron transfer distance calculations\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro mechanistic enzyme kinetics with mechanistic analysis, single lab\",\n      \"pmids\": [\"32370303\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"P. falciparum FNR catalyzes redox cycling of the antimalarial compound plasmodione (PD) in the presence of NADPH and oxygen, generating both key metabolites PD-bzol (benzylic alcohol) and PDO (3-benzoylmenadione) via a semiquinone radical intermediate. This FNR-mediated redox cycling generates reactive oxygen species (ROS) in the apicoplast, as demonstrated using a genetically encoded glutathione redox sensor in live parasites.\",\n      \"method\": \"In vitro enzyme redox cycling assay, LC-MS metabolite detection, live parasite imaging with genetically encoded redox sensor (hGrx1-roGFP2) in transgenic 3D7 P. falciparum\",\n      \"journal\": \"ACS infectious diseases\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution plus live parasite validation with orthogonal methods, single lab\",\n      \"pmids\": [\"33855850\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Three chemically reactive residues are important for P. falciparum FNR activity: Cys99 (active-site, responsible for hydride transfer), Cys284 (whose oxidation leads to inactive dimer), and His286 (NADPH binding). Both cysteines are promising targets for covalent inhibition, as shown using residue-specific chemical reagents.\",\n      \"method\": \"Site-directed mutagenesis, residue-specific chemical modification, enzymatic activity assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — mechanistic residue identification via chemical modification and mutagenesis, single lab, abstract-level detail\",\n      \"pmids\": [\"34509083\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Genetic deletion of FNR in P. falciparum (using an apicoplast metabolic bypass line) demonstrated that FNR is essential for blood-stage parasite survival but is not required for apicoplast maintenance. The Fd/FNR system provides reducing power to certain downstream iron-sulfur cluster proteins that are individually essential for parasite survival.\",\n      \"method\": \"Genetic deletion (conditional KO in PfMev apicoplast bypass line), growth/viability assays, double deletion epistasis with FeS transfer proteins SufA and NfuApi\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic deletion with defined phenotypic readout (essentiality), apicoplast bypass system controls, epistasis analysis, replicated across multiple gene deletions\",\n      \"pmids\": [\"35164549\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"P. falciparum FNR (ptFNR) can functionally replace the endogenous E. coli flavodoxin reductase in an E. coli complementation system, where bacterial growth depends on ptFd, ptFNR, and IspH from P. falciparum reconstituting the last step of the MEP isoprenoid biosynthesis pathway. This validated an in situ screening platform for MEP pathway inhibitors and functional mutations.\",\n      \"method\": \"E. coli complementation (genetic reconstitution), bacterial growth assays, LC-MS metabolite analysis, validation in conditional T. gondii Fd KO strain\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — functional reconstitution in heterologous system with growth readout and metabolomic validation, confirmed in parasites\",\n      \"pmids\": [\"40967433\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"P. falciparum FNR (PF3D7_0623200) is a FAD-containing, apicoplast-localized, plant-type NADPH-dependent oxidoreductase that is essential for blood-stage parasite survival; it transfers electrons from NADPH via FAD to ferredoxin (which then reduces downstream iron-sulfur cluster enzymes including LytB of the MEP isoprenoid pathway), forms an inactive disulfide-stabilized dimer at Cys284/Cys99 under oxidizing conditions, uses Tyr258 and His286/Lys249 for NADPH specificity and hydride transfer, and also catalyzes single-electron reduction of redox-cycling xenobiotics (quinones, nitroaromatics, aromatic N-oxides) via a ping-pong mechanism.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_0623200 (FNR) is a nuclear-encoded, plant-type ferredoxin-NADP+ reductase that is targeted to the apicoplast via an N-terminal bipartite transit peptide and supplies reducing power for apicoplast biosynthesis [#0]. It initiates an NADPH→FNR→ferredoxin electron transfer cascade in which FNR selectively reduces P. falciparum ferredoxin, which in turn delivers electrons to downstream iron-sulfur cluster enzymes; reconstitution showed this system is the physiological electron donor required for activity of LytB/IspH, the terminal enzyme of the DOXP/MEP isoprenoid pathway [#1, #2, #14]. Genetic deletion in an apicoplast metabolic bypass line established that FNR is essential for blood-stage survival by feeding reducing power to individually essential Fe-S cluster proteins, while being dispensable for apicoplast maintenance itself [#13]. Structurally, FNR forms a covalent dimer stabilized by an intermolecular disulfide involving Cys99/Cys284; this dimer is essentially inactive and forms under oxidizing conditions (H2O2), but is reversed by disulfide reduction (glutathione, lipoate), pointing to redox-regulated quaternary structure [#3, #5, #12]. Coenzyme specificity and hydride transfer depend on defined active-site residues: Tyr258 is the primary determinant of NADPH over NADH selectivity, His286 provides binding energy and orients the nicotinamide ring for hydride transfer, and Lys249 recognizes the 2'-phosphate of NADPH [#7, #8]. Basic residues on the FAD-binding face, including a Plasmodium-specific insertion, engage acidic patches on ferredoxin (notably Glu29) to confer the high-affinity, species-specific Fd:FNR interaction [#4, #9]. Beyond its physiological cascade, FNR catalyzes single-electron reduction of redox-cycling xenobiotics—quinones, nitroaromatics, and aromatic N-oxides—via a ping-pong mechanism, generating semiquinone radicals and apicoplast ROS, a property exploited by the antimalarial plasmodione [#6, #10, #11].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established that FNR is a nuclear-encoded plant-type reductase trafficked to the apicoplast, defining where in the parasite its redox chemistry operates.\",\n      \"evidence\": \"Cloning, recombinant expression, and Western blot showing transit-peptide processing plus phylogenetic analysis\",\n      \"pmids\": [\"11056177\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not identify the physiological electron acceptor or downstream pathway\", \"Import mechanism inferred from processing, not directly traced\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Answered what FNR's reducing power is used for by placing it at the head of an NADPH→FNR→Fd chain that drives the terminal MEP isoprenoid enzyme LytB.\",\n      \"evidence\": \"In vitro reconstitution with defined components and demonstration of a stable LytB-ferredoxin complex\",\n      \"pmids\": [\"16289098\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological essentiality not yet demonstrated in parasites\", \"Kinetic parameters of the full cascade not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Confirmed the selective electron flow from FNR to its cognate ferredoxin and provided structural context for the redox partner.\",\n      \"evidence\": \"Reconstituted NADPH-dependent cytochrome c reduction assay and X-ray structure of P. falciparum ferredoxin\",\n      \"pmids\": [\"17251200\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Interface residues on FNR not yet mapped\", \"FNR structure not solved in this study\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Revealed the structural basis of FNR's redox-sensitive quaternary regulation—a disulfide-linked, inactive dimer whose formation is coupled to NADP(H) adenylate binding.\",\n      \"evidence\": \"Crystal structures of free and 2'-phospho-AMP-bound FNR with kinetic and solution redox studies\",\n      \"pmids\": [\"17258767\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of dimerization not established\", \"Cys284 contribution not yet distinguished\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined the electrostatic docking sites on ferredoxin, showing Glu29 as the dominant residue governing the Fd:FNR interaction.\",\n      \"evidence\": \"NMR chemical shift perturbation, Fd mutagenesis, and electron transfer/affinity assays\",\n      \"pmids\": [\"17938142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Complementary interface residues on FNR not identified in this work\", \"No co-crystal of the complex\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Explained the enzyme's unusually low catalytic efficiency and tied its inactivation to oxidative disulfide dimer formation reversible by cellular thiols.\",\n      \"evidence\": \"Steady-state/rapid-reaction kinetics, redox potential determination, and oxidizing/reducing treatments\",\n      \"pmids\": [\"19523113\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether redox regulation operates in vivo not shown\", \"Biological trigger for oxidation not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Dissected the dual role of His286 and the role of Lys249 in NADPH recognition and productive hydride-transfer geometry.\",\n      \"evidence\": \"Site-directed mutagenesis with kinetics and mutant 2'-P-AMP co-crystal structures\",\n      \"pmids\": [\"19736991\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Effect on ferredoxin reduction in the full cascade not measured\", \"Contribution to coenzyme discrimination not isolated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed FNR can perform single-electron quinone reduction, framing it as a mediator of antiplasmodial redox-cycling drug chemistry.\",\n      \"evidence\": \"In vitro single-electron reduction rate measurements with statistical analysis of antiplasmodial activity\",\n      \"pmids\": [\"19919822\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cellular relevance of quinone reduction not demonstrated in parasites here\", \"Aziridinyl-quinone two-electron pathway inferred, not directly resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"FcB1\"}]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified Tyr258 as the principal determinant of NADPH-over-NADH specificity, acting by stabilizing the catalytically competent coenzyme conformation.\",\n      \"evidence\": \"Y258F mutagenesis with steady-state and rapid kinetics, active-site titrations, and anaerobic photoreduction\",\n      \"pmids\": [\"22519987\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Impact on physiological Fd reduction rate not quantified\", \"No structure of the Y258F mutant\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Mapped the complementary FNR interface, showing Plasmodium-specific basic residues on the FAD-binding face drive the high-affinity, species-specific ferredoxin interaction.\",\n      \"evidence\": \"Comprehensive FNR mutagenesis with kinetic, affinity, and thermodynamic binding analyses\",\n      \"pmids\": [\"29688515\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No experimental structure of the Fd:FNR complex\", \"Whether this specificity can be exploited for inhibition untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Generalized FNR's xenobiotic-reducing activity to quinones, nitroaromatics, and aromatic N-oxides via a ping-pong mechanism, with ferredoxin providing an additional reduction route.\",\n      \"evidence\": \"In vitro kinetic analysis of single-electron reduction and electron-transfer distance calculations\",\n      \"pmids\": [\"32370303\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo contribution to drug activation not addressed here\", \"Rate-limiting FAD reoxidation step only partially resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated in live parasites that FNR-driven redox cycling of the antimalarial plasmodione generates apicoplast ROS, linking its enzymology to a drug mechanism of action.\",\n      \"evidence\": \"In vitro redox cycling with LC-MS metabolite detection and live-parasite imaging with an hGrx1-roGFP2 redox sensor in transgenic 3D7\",\n      \"pmids\": [\"33855850\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of FNR versus other flavoenzymes in cells not quantified\", \"Downstream ROS targets not identified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Nominated Cys99, Cys284, and His286 as chemically reactive, functionally critical residues and candidate covalent-inhibition sites.\",\n      \"evidence\": \"Site-directed mutagenesis with residue-specific chemical modification and activity assays\",\n      \"pmids\": [\"34509083\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No inhibitor with parasite activity demonstrated\", \"Abstract-level mechanistic detail; selectivity over host reductases untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Provided direct genetic proof that FNR is essential for blood-stage survival through supply of reducing power to essential Fe-S cluster proteins, while being dispensable for apicoplast maintenance.\",\n      \"evidence\": \"Conditional deletion in the PfMev apicoplast metabolic bypass line with growth assays and epistasis against SufA and NfuApi\",\n      \"pmids\": [\"35164549\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The specific essential Fe-S enzymes downstream not fully enumerated\", \"Non-MEP essential functions not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established a heterologous reconstitution platform in which FNR, ferredoxin, and IspH from P. falciparum functionally replace E. coli flavodoxin reductase, enabling in situ MEP-pathway inhibitor screening.\",\n      \"evidence\": \"E. coli complementation with growth and LC-MS readouts, validated in a conditional T. gondii Fd KO strain\",\n      \"pmids\": [\"40967433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Not a native parasite context for kinetics\", \"Screening hits against FNR itself not reported\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FNR's redox-regulated dimerization and xenobiotic single-electron chemistry are controlled and exploited in vivo, and whether its species-specific ferredoxin interface can be pharmacologically targeted, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental structure of the Fd:FNR complex\", \"In vivo trigger and physiological role of the inactive disulfide dimer not established\", \"No validated FNR-selective inhibitor with parasite efficacy\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004324\", \"supporting_discovery_ids\": [1, 2, 5, 7, 8]},\n      {\"term_id\": \"GO:0050660\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"GO:0016651\", \"supporting_discovery_ids\": [1, 2, 10]},\n      {\"term_id\": \"GO:0050661\", \"supporting_discovery_ids\": [7, 8]},\n      {\"term_id\": \"GO:0055114\", \"supporting_discovery_ids\": [6, 10, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020011\", \"supporting_discovery_ids\": [0, 11, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0019288\", \"supporting_discovery_ids\": [1, 14]},\n      {\"term_id\": \"GO:0022900\", \"supporting_discovery_ids\": [1, 2, 13]},\n      {\"term_id\": \"GO:0016226\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"complexes\": [\n      \"Redox-sensitive covalent FNR homodimer stabilized by an intermolecular disulfide (Cys99/Cys284), catalytically inactive and reversed by thiol reduction [#3, #5, #12]\",\n      \"FNR functions with ferredoxin as an NADPH-dependent electron transfer pair; ferredoxin further forms a stable complex with LytB/IspH [#1, #2]\"\n    ],\n    \"partners\": [\n      \"P. falciparum ferredoxin (Fd) — cognate electron acceptor via acidic patches including Glu29 and FNR basic FAD-face residues [#2, #4, #9]\",\n      \"LytB/IspH (terminal MEP pathway enzyme) — downstream acceptor of the FNR→Fd cascade [#1, #14]\",\n      \"Downstream essential Fe-S cluster proteins (functional epistasis with SufA and NfuApi) [#13]\"\n    ],\n    \"other_free_text\": [\n      \"Tyr258 is the primary determinant of NADPH over NADH coenzyme specificity [#8]\",\n      \"His286 provides NADPH binding energy and orients the nicotinamide ring for hydride transfer; Lys249 recognizes the NADPH 2'-phosphate [#7]\",\n      \"Exhibits low catalytic efficiency due to slow hydride transfer and a destabilized FAD semiquinone [#5]\",\n      \"Catalyzes single-electron reduction of quinones, nitroaromatics, and aromatic N-oxides by a ping-pong mechanism; ferredoxin stimulates these reactions [#6, #10]\",\n      \"Mediates redox cycling of the antimalarial plasmodione, generating apicoplast ROS in live parasites [#11]\",\n      \"Essential for blood-stage survival but dispensable for apicoplast maintenance [#13]\",\n      \"Functionally reconstitutable in E. coli as part of a P. falciparum Fd/FNR/IspH MEP module [#14]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0623200","name":null,"product":"ferredoxin--NADP reductase","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1122100","name":null,"product":"ferredoxin--NADP reductase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1127000","name":null,"product":"ferredoxin--NADP reductase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"FNR","evaluation":null}