{"gene":"PF3D7_0716600","run_date":"2026-09-08T12:51:27","timeline":{"discoveries":[{"year":2013,"finding":"P. falciparum SufS localizes exclusively to the apicoplast (not mitochondria) and has cysteine desulfurase activity, demonstrated by complementation assay. Disruption of the Suf pathway with a dominant negative mutant caused loss of the apicoplast organelle and its organellar genome, a phenotype rescued by IPP supplementation, establishing SufS/the Suf pathway as essential for apicoplast maintenance beyond its role in isoprenoid biosynthesis.","method":"Fluorescence localization, complementation assay, dominant-negative mutant with IPP rescue","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (localization, complementation assay, genetic disruption with specific rescue), single lab but rigorous controls","pmids":["24086138"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"P. falciparum SufS has cysteine desulfurase activity that is greatly enhanced by its partner PfSufE; the PfSufS–PfSufE complex is detected in vivo. Structural modeling places conserved cysteine residues of PfSufS and PfSufE in proximity, consistent with sulfide transfer from the PLP-bound active site of PfSufS to PfSufE. The PLP inhibitor d-cycloserine forms an adduct with PfSufS-bound PLP and inhibits sulfide release from l-cysteine.","method":"In vitro cysteine desulfurase activity assay, co-immunoprecipitation (in vivo complex detection), structural modeling, inhibitor (d-cycloserine) biochemical assay","journal":"Antimicrobial agents and chemotherapy","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro enzymatic assay, in vivo complex detection, structural modeling with functional validation; single lab, multiple orthogonal methods","pmids":["24709262"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"In P. berghei, SufS (SUFS) is refractory to targeted gene deletion during asexual blood stages, and all five tagged SUF proteins including SufS localize to the apicoplast, validating SufS as essential for blood-stage parasite survival.","method":"Targeted gene deletion attempts, fluorescent tagging and localization","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic deletion attempted in multiple SUF members, fluorescent localization; single lab, multiple SUFs assessed together","pmids":["24586983"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2017,"finding":"Conditional knockout of SufS by selective excision in mosquito stages of P. berghei severely impaired sporozoite development in oocysts, establishing essentiality of SufS (and the SUF machinery) in the insect vector life-cycle stage.","method":"Conditional knockout (Cre-lox selective excision) in P. berghei mosquito stages, sporozoite development assay","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional genetic knockout with defined developmental phenotype, single lab","pmids":["28695709"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2019,"finding":"In P. vivax clinical isolates, SufS and SufE interact in vitro to form a complex responsible for sulfur mobilization in the apicoplast, and this interaction is conserved despite sequence variations in pathway proteins relative to lab strains.","method":"In vitro protein interaction assay using P. vivax clinical isolate proteins","journal":"Experimental parasitology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single in vitro interaction assay, single lab, clinical isolate material","pmids":["30721667"],"is_preprint":false,"attribution":[{"species":"Plasmodium vivax","strain":""}]},{"year":2022,"finding":"D-cycloserine (DCS) and L-cycloserine (LCS) inhibit SufS cysteine desulfurase activity via distinct mechanisms: DCS yields a pyridoxamine-5'-phosphate (PMP) dead-end product, while LCS yields a PMP-3-hydroxyisoxazole adduct (PMP-isoxazole). Conserved His and Arg residues at the active site are key determinants of these distinct inhibition mechanisms, established by biochemical and structural analysis of B. subtilis SufS variants (informing P. falciparum SufS drug design).","method":"Biochemical inhibition assays, X-ray crystallography, active-site mutagenesis of B. subtilis SufS (with relevance to P. falciparum SufS)","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — structure + mutagenesis but performed on B. subtilis SufS as a surrogate for P. falciparum SufS; mechanistic insight directly extrapolated to PfSufS but not confirmed experimentally in the parasite","pmids":["35395703"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"Deletion of SufS in P. falciparum disrupts the apicoplast organelle and causes loss of the organellar genome, a phenotype distinct from deletion of other FeS pathway components. The requirement of SufS for organelle maintenance is not due to its role in FeS biosynthesis but rather its function in providing sulfur to MnmA, a tRNA-modifying enzyme localized to the apicoplast. Complementation with a bacterial MnmA and its cognate cysteine desulfurase rescued the phenotype, strongly establishing that P. falciparum SufS provides sulfur for both FeS cluster biosynthesis and tRNA modification (s2U) in the apicoplast.","method":"Conditional gene deletion (chemical bypass), organelle/genome integrity assays, localization of MnmA, bacterial complementation assay","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (deletion, complementation, localization), cross-species complementation confirms mechanism, single lab but rigorous experimental design","pmids":["37166116"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"SufS (alongside MnmA) was previously shown to catalyze the s2U tRNA modification in the P. falciparum apicoplast; deletion of SufS causes apicoplast disruption and parasite death, a phenotype mirrored by deletion of MnmA, MnmE, and MnmG, supporting that SufS supplies sulfur specifically for xm5s2U tRNA modification in the apicoplast.","method":"Comparative genomics, genetic deletion with apicoplast-integrity phenotype readout (corroborating prior SufS findings)","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic deletion with defined phenotype; preprint, single lab; corroborates published eLife findings","pmids":["39763917"],"is_preprint":true,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"P. falciparum SufS (PF3D7_0716600) is a PLP-dependent cysteine desulfurase that localizes exclusively to the apicoplast, where it forms a complex with SufE to mobilize sulfur as the first step of Fe-S cluster biosynthesis via the SUF pathway; critically, SufS also provides sulfur to the tRNA-modifying enzyme MnmA for s2U/xm5s2U modification of apicoplast tRNAs, and this dual role in both FeS biogenesis and tRNA modification explains why SufS deletion uniquely disrupts the apicoplast organelle and organellar genome, making it essential for parasite survival across blood and mosquito stages."},"narrative":{"mechanistic_narrative":"PF3D7_0716600 (SufS) is a PLP-dependent cysteine desulfurase that localizes exclusively to the apicoplast, where it mobilizes sulfur from L-cysteine as the entry step of the SUF Fe-S cluster biosynthesis pathway and is essential for maintenance of the apicoplast organelle and its genome [PMID:24086138]. Its desulfurase activity is greatly enhanced by the partner SufE, with which it forms an in vivo complex; structural modeling places conserved cysteines of SufS and SufE in proximity, consistent with sulfide transfer from the PLP-bound SufS active site to SufE [PMID:24709262]. Beyond Fe-S biogenesis, SufS provides sulfur to the apicoplast tRNA-modifying enzyme MnmA for s2U/xm5s2U modification, and bacterial MnmA-plus-desulfurase complementation shows this tRNA-modification role—not Fe-S biosynthesis—accounts for the unique apicoplast- and organellar-genome-disrupting phenotype of SufS deletion [PMID:37166116, PMID:39763917]. This dual role makes SufS essential across the parasite life cycle: it is refractory to deletion in asexual blood stages and its conditional knockout impairs sporozoite development in the mosquito vector [PMID:24586983, PMID:28695709]. The PLP-directed inhibitors D- and L-cycloserine form adducts with SufS-bound PLP and block sulfide release, defining an antimalarial drug-target vulnerability [PMID:24709262, PMID:35395703].","teleology":[{"year":2013,"claim":"Established that SufS is an apicoplast-resident cysteine desulfurase and that its pathway is essential for organelle maintenance beyond isoprenoid biosynthesis, defining the first functional role for the gene.","evidence":"Fluorescence localization, complementation of desulfurase activity, dominant-negative disruption with IPP rescue in P. falciparum","pmids":["24086138"],"confidence":"High","gaps":["Did not resolve which downstream product of sulfur mobilization is required for organelle maintenance","Enzymatic partners not yet identified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"Identified SufE as the functional partner that enhances SufS desulfurase activity and defined the sulfide-transfer geometry and PLP-directed inhibition, converting a lone enzyme into a characterized two-component sulfur-mobilization module.","evidence":"In vitro desulfurase assays, in vivo co-immunoprecipitation, structural modeling, and D-cycloserine adduct/inhibition assays in P. falciparum","pmids":["24709262"],"confidence":"High","gaps":["Sulfide transfer to SufE inferred from modeling, not from a solved SufS-SufE structure","Downstream Fe-S assembly steps not reconstituted"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"Genetic evidence that SufS is required for asexual blood-stage survival, establishing essentiality in the rodent malaria model.","evidence":"Failed targeted gene deletion and fluorescent apicoplast localization of tagged SUF proteins including SufS in P. berghei","pmids":["24586983"],"confidence":"Medium","gaps":["Refractoriness to deletion does not by itself define the essential molecular function","Assessed alongside other SUF members rather than SufS in isolation"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2017,"claim":"Extended essentiality of SufS from blood stages to the mosquito vector, showing the gene is required across life-cycle transitions.","evidence":"Cre-lox conditional knockout in P. berghei mosquito stages with sporozoite development assay","pmids":["28695709"],"confidence":"High","gaps":["Molecular basis of the sporozoite defect not resolved","Whether the requirement reflects Fe-S or tRNA-modification function not addressed"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2019,"claim":"Showed the SufS-SufE sulfur-mobilization interaction is conserved in clinical parasite material despite sequence variation from lab strains.","evidence":"In vitro protein interaction assay using P. vivax clinical-isolate proteins","pmids":["30721667"],"confidence":"Low","gaps":["Single in vitro interaction assay without reciprocal or in vivo validation","No enzymatic or phenotypic readout for the P. vivax proteins"],"attribution":[{"species":"Plasmodium vivax","strain":""}]},{"year":2022,"claim":"Defined the distinct mechanisms by which D- and L-cycloserine inactivate SufS PLP chemistry, informing structure-based antimalarial design.","evidence":"Biochemical inhibition, X-ray crystallography, and active-site mutagenesis using B. subtilis SufS as a surrogate for the P. falciparum enzyme","pmids":["35395703"],"confidence":"Medium","gaps":["Mechanistic detail extrapolated from a bacterial surrogate, not confirmed in P. falciparum SufS","Selectivity against host desulfurases not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"claim":"Resolved why SufS deletion is uniquely lethal by showing its essential role is supplying sulfur to the tRNA-modifying enzyme MnmA rather than to Fe-S biosynthesis, distinguishing SufS from other pathway components.","evidence":"Conditional gene deletion with chemical bypass, organelle/genome integrity assays, MnmA localization, and cross-species bacterial MnmA-plus-desulfurase complementation in P. falciparum","pmids":["37166116"],"confidence":"High","gaps":["Direct sulfur-transfer between SufS and MnmA not biochemically reconstituted","Relative contribution of Fe-S versus tRNA-modification pathways to viability not quantified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"claim":"Corroborated that SufS supplies sulfur for xm5s2U apicoplast tRNA modification by showing its deletion phenotype is mirrored by loss of MnmA, MnmE, and MnmG.","evidence":"Comparative genomics and genetic deletion with apicoplast-integrity readout in P. falciparum (preprint)","pmids":["39763917"],"confidence":"Medium","gaps":["Preprint, single lab","Does not add direct biochemical demonstration of SufS-to-MnmA sulfur transfer"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How SufS partitions its mobilized sulfur between SufE/Fe-S assembly and MnmA/tRNA modification, and whether a direct SufS-MnmA transfer complex forms, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No reconstituted SufS-MnmA sulfur-transfer assay","No solved structure of SufS in complex with SufE or MnmA","Mechanism directing sulfur to competing acceptors unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["SufS-SufE sulfur-mobilization complex (in vivo, P. falciparum) [#1]"],"partners":["SUFE (ENHANCES DESULFURASE ACTIVITY; SULFIDE ACCEPTOR) [#1, #4]","MNMA (TRNA-MODIFYING ENZYME; SULFUR ACCEPTOR FOR S2U/XM5S2U MODIFICATION) [#6, #7]"],"other_free_text":["Deletion of SufS uniquely disrupts the apicoplast and causes loss of the organellar genome, a phenotype attributable to its tRNA-modification (MnmA) role rather than Fe-S biosynthesis [#6].","Essential across life-cycle stages: refractory to blood-stage deletion in P. berghei and required for mosquito-stage sporozoite development [#2, #3].","PLP-directed inhibitors D- and L-cycloserine form adducts with SufS-bound PLP and block sulfide release, marking a drug-target vulnerability [#1, #5]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"24086138","id":"PMC_24086138","title":"The suf iron-sulfur cluster synthesis pathway is required for apicoplast maintenance in malaria parasites.","date":"2013","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/24086138","citation_count":92,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["SufS","cysteine desulfurase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"11555280","id":"PMC_11555280","title":"Nifs and Sufs in malaria.","date":"2001","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/11555280","citation_count":80,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["SufS"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"24709262","id":"PMC_24709262","title":"Sulfur mobilization for Fe-S cluster assembly by the essential SUF pathway in the Plasmodium falciparum apicoplast and its inhibition.","date":"2014","source":"Antimicrobial agents and chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/24709262","citation_count":40,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["SufS","cysteine desulfurase","PfSufS"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"28695709","id":"PMC_28695709","title":"[Fe-S] cluster assembly in the apicoplast and its indispensability in mosquito stages of the malaria parasite.","date":"2017","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/28695709","citation_count":30,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["SufS"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"24586983","id":"PMC_24586983","title":"Identification of vital and dispensable sulfur utilization factors in the Plasmodium apicoplast.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24586983","citation_count":27,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["SufS"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37166116","id":"PMC_37166116","title":"The Plasmodium falciparum apicoplast cysteine desulfurase provides sulfur for both iron-sulfur cluster assembly and tRNA modification.","date":"2023","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/37166116","citation_count":13,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["SufS","cysteine desulfurase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35395703","id":"PMC_35395703","title":"Cycloserine enantiomers inhibit PLP-dependent cysteine desulfurase SufS via distinct mechanisms.","date":"2022","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/35395703","citation_count":11,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["SufS","cysteine desulfurase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30721667","id":"PMC_30721667","title":"Functional analysis of iron-sulfur cluster biogenesis (SUF pathway) from Plasmodium vivax clinical isolates.","date":"2019","source":"Experimental parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/30721667","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["SufS","cysteine desulfurase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"39763917","id":"PMC_39763917","title":"tRNA modifying enzymes MnmE and MnmG are essential for Plasmodium falciparum apicoplast maintenance.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/39763917","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["SufS"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7175,"output_tokens":2373,"usd":0.02856,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7760,"output_tokens":3439,"usd":0.062387,"stage2_stop_reason":"end_turn"},"total_usd":0.090947,"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\": 2013,\n      \"finding\": \"P. falciparum SufS localizes exclusively to the apicoplast (not mitochondria) and has cysteine desulfurase activity, demonstrated by complementation assay. Disruption of the Suf pathway with a dominant negative mutant caused loss of the apicoplast organelle and its organellar genome, a phenotype rescued by IPP supplementation, establishing SufS/the Suf pathway as essential for apicoplast maintenance beyond its role in isoprenoid biosynthesis.\",\n      \"method\": \"Fluorescence localization, complementation assay, dominant-negative mutant with IPP rescue\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (localization, complementation assay, genetic disruption with specific rescue), single lab but rigorous controls\",\n      \"pmids\": [\"24086138\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"P. falciparum SufS has cysteine desulfurase activity that is greatly enhanced by its partner PfSufE; the PfSufS–PfSufE complex is detected in vivo. Structural modeling places conserved cysteine residues of PfSufS and PfSufE in proximity, consistent with sulfide transfer from the PLP-bound active site of PfSufS to PfSufE. The PLP inhibitor d-cycloserine forms an adduct with PfSufS-bound PLP and inhibits sulfide release from l-cysteine.\",\n      \"method\": \"In vitro cysteine desulfurase activity assay, co-immunoprecipitation (in vivo complex detection), structural modeling, inhibitor (d-cycloserine) biochemical assay\",\n      \"journal\": \"Antimicrobial agents and chemotherapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro enzymatic assay, in vivo complex detection, structural modeling with functional validation; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"24709262\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In P. berghei, SufS (SUFS) is refractory to targeted gene deletion during asexual blood stages, and all five tagged SUF proteins including SufS localize to the apicoplast, validating SufS as essential for blood-stage parasite survival.\",\n      \"method\": \"Targeted gene deletion attempts, fluorescent tagging and localization\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic deletion attempted in multiple SUF members, fluorescent localization; single lab, multiple SUFs assessed together\",\n      \"pmids\": [\"24586983\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Conditional knockout of SufS by selective excision in mosquito stages of P. berghei severely impaired sporozoite development in oocysts, establishing essentiality of SufS (and the SUF machinery) in the insect vector life-cycle stage.\",\n      \"method\": \"Conditional knockout (Cre-lox selective excision) in P. berghei mosquito stages, sporozoite development assay\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional genetic knockout with defined developmental phenotype, single lab\",\n      \"pmids\": [\"28695709\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In P. vivax clinical isolates, SufS and SufE interact in vitro to form a complex responsible for sulfur mobilization in the apicoplast, and this interaction is conserved despite sequence variations in pathway proteins relative to lab strains.\",\n      \"method\": \"In vitro protein interaction assay using P. vivax clinical isolate proteins\",\n      \"journal\": \"Experimental parasitology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single in vitro interaction assay, single lab, clinical isolate material\",\n      \"pmids\": [\"30721667\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium vivax\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"D-cycloserine (DCS) and L-cycloserine (LCS) inhibit SufS cysteine desulfurase activity via distinct mechanisms: DCS yields a pyridoxamine-5'-phosphate (PMP) dead-end product, while LCS yields a PMP-3-hydroxyisoxazole adduct (PMP-isoxazole). Conserved His and Arg residues at the active site are key determinants of these distinct inhibition mechanisms, established by biochemical and structural analysis of B. subtilis SufS variants (informing P. falciparum SufS drug design).\",\n      \"method\": \"Biochemical inhibition assays, X-ray crystallography, active-site mutagenesis of B. subtilis SufS (with relevance to P. falciparum SufS)\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — structure + mutagenesis but performed on B. subtilis SufS as a surrogate for P. falciparum SufS; mechanistic insight directly extrapolated to PfSufS but not confirmed experimentally in the parasite\",\n      \"pmids\": [\"35395703\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Deletion of SufS in P. falciparum disrupts the apicoplast organelle and causes loss of the organellar genome, a phenotype distinct from deletion of other FeS pathway components. The requirement of SufS for organelle maintenance is not due to its role in FeS biosynthesis but rather its function in providing sulfur to MnmA, a tRNA-modifying enzyme localized to the apicoplast. Complementation with a bacterial MnmA and its cognate cysteine desulfurase rescued the phenotype, strongly establishing that P. falciparum SufS provides sulfur for both FeS cluster biosynthesis and tRNA modification (s2U) in the apicoplast.\",\n      \"method\": \"Conditional gene deletion (chemical bypass), organelle/genome integrity assays, localization of MnmA, bacterial complementation assay\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (deletion, complementation, localization), cross-species complementation confirms mechanism, single lab but rigorous experimental design\",\n      \"pmids\": [\"37166116\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SufS (alongside MnmA) was previously shown to catalyze the s2U tRNA modification in the P. falciparum apicoplast; deletion of SufS causes apicoplast disruption and parasite death, a phenotype mirrored by deletion of MnmA, MnmE, and MnmG, supporting that SufS supplies sulfur specifically for xm5s2U tRNA modification in the apicoplast.\",\n      \"method\": \"Comparative genomics, genetic deletion with apicoplast-integrity phenotype readout (corroborating prior SufS findings)\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic deletion with defined phenotype; preprint, single lab; corroborates published eLife findings\",\n      \"pmids\": [\"39763917\"],\n      \"is_preprint\": true,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"P. falciparum SufS (PF3D7_0716600) is a PLP-dependent cysteine desulfurase that localizes exclusively to the apicoplast, where it forms a complex with SufE to mobilize sulfur as the first step of Fe-S cluster biosynthesis via the SUF pathway; critically, SufS also provides sulfur to the tRNA-modifying enzyme MnmA for s2U/xm5s2U modification of apicoplast tRNAs, and this dual role in both FeS biogenesis and tRNA modification explains why SufS deletion uniquely disrupts the apicoplast organelle and organellar genome, making it essential for parasite survival across blood and mosquito stages.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_0716600 (SufS) is a PLP-dependent cysteine desulfurase that localizes exclusively to the apicoplast, where it mobilizes sulfur from L-cysteine as the entry step of the SUF Fe-S cluster biosynthesis pathway and is essential for maintenance of the apicoplast organelle and its genome [#0]. Its desulfurase activity is greatly enhanced by the partner SufE, with which it forms an in vivo complex; structural modeling places conserved cysteines of SufS and SufE in proximity, consistent with sulfide transfer from the PLP-bound SufS active site to SufE [#1]. Beyond Fe-S biogenesis, SufS provides sulfur to the apicoplast tRNA-modifying enzyme MnmA for s2U/xm5s2U modification, and bacterial MnmA-plus-desulfurase complementation shows this tRNA-modification role—not Fe-S biosynthesis—accounts for the unique apicoplast- and organellar-genome-disrupting phenotype of SufS deletion [#6, #7]. This dual role makes SufS essential across the parasite life cycle: it is refractory to deletion in asexual blood stages and its conditional knockout impairs sporozoite development in the mosquito vector [#2, #3]. The PLP-directed inhibitors D- and L-cycloserine form adducts with SufS-bound PLP and block sulfide release, defining an antimalarial drug-target vulnerability [#1, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Established that SufS is an apicoplast-resident cysteine desulfurase and that its pathway is essential for organelle maintenance beyond isoprenoid biosynthesis, defining the first functional role for the gene.\",\n      \"evidence\": \"Fluorescence localization, complementation of desulfurase activity, dominant-negative disruption with IPP rescue in P. falciparum\",\n      \"pmids\": [\"24086138\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which downstream product of sulfur mobilization is required for organelle maintenance\", \"Enzymatic partners not yet identified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified SufE as the functional partner that enhances SufS desulfurase activity and defined the sulfide-transfer geometry and PLP-directed inhibition, converting a lone enzyme into a characterized two-component sulfur-mobilization module.\",\n      \"evidence\": \"In vitro desulfurase assays, in vivo co-immunoprecipitation, structural modeling, and D-cycloserine adduct/inhibition assays in P. falciparum\",\n      \"pmids\": [\"24709262\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Sulfide transfer to SufE inferred from modeling, not from a solved SufS-SufE structure\", \"Downstream Fe-S assembly steps not reconstituted\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Genetic evidence that SufS is required for asexual blood-stage survival, establishing essentiality in the rodent malaria model.\",\n      \"evidence\": \"Failed targeted gene deletion and fluorescent apicoplast localization of tagged SUF proteins including SufS in P. berghei\",\n      \"pmids\": [\"24586983\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Refractoriness to deletion does not by itself define the essential molecular function\", \"Assessed alongside other SUF members rather than SufS in isolation\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended essentiality of SufS from blood stages to the mosquito vector, showing the gene is required across life-cycle transitions.\",\n      \"evidence\": \"Cre-lox conditional knockout in P. berghei mosquito stages with sporozoite development assay\",\n      \"pmids\": [\"28695709\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of the sporozoite defect not resolved\", \"Whether the requirement reflects Fe-S or tRNA-modification function not addressed\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed the SufS-SufE sulfur-mobilization interaction is conserved in clinical parasite material despite sequence variation from lab strains.\",\n      \"evidence\": \"In vitro protein interaction assay using P. vivax clinical-isolate proteins\",\n      \"pmids\": [\"30721667\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single in vitro interaction assay without reciprocal or in vivo validation\", \"No enzymatic or phenotypic readout for the P. vivax proteins\"],\n      \"attribution\": [{\"species\": \"Plasmodium vivax\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined the distinct mechanisms by which D- and L-cycloserine inactivate SufS PLP chemistry, informing structure-based antimalarial design.\",\n      \"evidence\": \"Biochemical inhibition, X-ray crystallography, and active-site mutagenesis using B. subtilis SufS as a surrogate for the P. falciparum enzyme\",\n      \"pmids\": [\"35395703\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic detail extrapolated from a bacterial surrogate, not confirmed in P. falciparum SufS\", \"Selectivity against host desulfurases not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved why SufS deletion is uniquely lethal by showing its essential role is supplying sulfur to the tRNA-modifying enzyme MnmA rather than to Fe-S biosynthesis, distinguishing SufS from other pathway components.\",\n      \"evidence\": \"Conditional gene deletion with chemical bypass, organelle/genome integrity assays, MnmA localization, and cross-species bacterial MnmA-plus-desulfurase complementation in P. falciparum\",\n      \"pmids\": [\"37166116\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct sulfur-transfer between SufS and MnmA not biochemically reconstituted\", \"Relative contribution of Fe-S versus tRNA-modification pathways to viability not quantified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Corroborated that SufS supplies sulfur for xm5s2U apicoplast tRNA modification by showing its deletion phenotype is mirrored by loss of MnmA, MnmE, and MnmG.\",\n      \"evidence\": \"Comparative genomics and genetic deletion with apicoplast-integrity readout in P. falciparum (preprint)\",\n      \"pmids\": [\"39763917\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, single lab\", \"Does not add direct biochemical demonstration of SufS-to-MnmA sulfur transfer\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SufS partitions its mobilized sulfur between SufE/Fe-S assembly and MnmA/tRNA modification, and whether a direct SufS-MnmA transfer complex forms, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reconstituted SufS-MnmA sulfur-transfer assay\", \"No solved structure of SufS in complex with SufE or MnmA\", \"Mechanism directing sulfur to competing acceptors unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0031071\", \"supporting_discovery_ids\": [0, 1, 5, 6]},\n      {\"term_id\": \"GO:0030170\", \"supporting_discovery_ids\": [1, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020011\", \"supporting_discovery_ids\": [0, 2, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0016226\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0002143\", \"supporting_discovery_ids\": [6, 7]}\n    ],\n    \"complexes\": [\n      \"SufS-SufE sulfur-mobilization complex (in vivo, P. falciparum) [#1]\"\n    ],\n    \"partners\": [\n      \"SufE (enhances desulfurase activity; sulfide acceptor) [#1, #4]\",\n      \"MnmA (tRNA-modifying enzyme; sulfur acceptor for s2U/xm5s2U modification) [#6, #7]\"\n    ],\n    \"other_free_text\": [\n      \"Deletion of SufS uniquely disrupts the apicoplast and causes loss of the organellar genome, a phenotype attributable to its tRNA-modification (MnmA) role rather than Fe-S biosynthesis [#6].\",\n      \"Essential across life-cycle stages: refractory to blood-stage deletion in P. berghei and required for mosquito-stage sporozoite development [#2, #3].\",\n      \"PLP-directed inhibitors D- and L-cycloserine form adducts with SufS-bound PLP and block sulfide release, marking a drug-target vulnerability [#1, #5].\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0716600","name":null,"product":"cysteine desulfurase","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0614300","name":null,"product":"cysteine desulfurase","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0311200","name":null,"product":"cysteine desulfurase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"SufS","evaluation":null}