{"gene":"PF3D7_1320100","run_date":"2026-09-08T14:19:06","timeline":{"discoveries":[{"year":2016,"finding":"Crystal structure of P. falciparum ClpS (PF3D7_1320100) solved at 2.7 Å resolution reveals a hydrophobic N-degron binding pocket occluded by a conserved surface loop acting as a latch; despite the closed conformation in the crystal, solution binding assays show ClpS binds and discriminates peptides mimicking N-end rule substrates.","method":"X-ray crystallography (2.7 Å); solution peptide-binding assays","journal":"Protein science : a publication of the Protein Society","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with functional validation by solution binding assay in a single rigorous study","pmids":["26701219"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"The presence of an apicoplast targeting peptide in P. falciparum ClpS (PF3D7_1320100) indicates it localizes to the apicoplast, consistent with its predicted function as a substrate adaptor for the apicoplast Clp machinery.","method":"Sequence analysis of apicoplast targeting peptide (bioinformatic/structural study)","journal":"Protein science : a publication of the Protein Society","confidence":"Low","confidence_rationale":"Tier 4 / Weak — localization inferred from targeting peptide sequence, not confirmed by direct imaging or fractionation experiment","pmids":["26701219"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"Conditional mutants of P. falciparum ClpS (PF3D7_1320100, referred to as PfClpS in this study) demonstrate that ClpS is essential for apicoplast biogenesis in blood-stage parasites.","method":"Conditional (inducible) genetic knockdown/mutant with apicoplast biogenesis phenotypic readout","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional null mutant with defined organelle biogenesis phenotype in a rigorous study","pmids":["32482878"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"Affinity purification screens identified P. falciparum ClpS (PF3D7_1320100) as part of the apicoplast Clp complex, establishing its membership in a multi-subunit protease complex that includes PfClpP and PfClpC.","method":"Multiple affinity purification/mass spectrometry screens","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple independent affinity purification experiments converging on complex membership, but no reciprocal co-IP or reconstitution","pmids":["32482878"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"P. falciparum ClpS (PF3D7_1320100) is an apicoplast-localized N-end rule substrate adaptor that adopts a bacterial ClpS-like fold with a hydrophobic N-degron binding pocket (occluded in the crystal by a surface loop but open in solution), functions as part of the multi-subunit apicoplast Clp proteolytic complex (with PfClpP and PfClpC), and is essential for apicoplast biogenesis."},"narrative":{"mechanistic_narrative":"P. falciparum ClpS (PF3D7_1320100) is a substrate adaptor of the apicoplast Clp proteolytic machinery that is essential for apicoplast biogenesis in blood-stage parasites [PMID:32482878]. Its 2.7 Å crystal structure reveals a bacterial ClpS-like fold with a hydrophobic N-degron binding pocket; in the crystal this pocket is occluded by a conserved surface loop acting as a latch, yet solution binding assays show that ClpS binds and discriminates peptides mimicking N-end rule substrates, consistent with a role in recognizing and delivering N-degron-bearing substrates for proteolysis [PMID:26701219]. Affinity purification screens place ClpS within a multi-subunit apicoplast Clp complex that includes PfClpP and PfClpC [PMID:32482878]. Beyond its membership in this complex, its N-degron recognition activity, and its requirement for apicoplast biogenesis, no further mechanistic detail — including direct identification of its physiological substrates or reciprocal validation of its complex interactions — has been characterized in the available corpus.","teleology":[{"year":2016,"claim":"It was unknown whether Plasmodium ClpS retained the structural machinery to act as an N-end rule substrate adaptor; the crystal structure and solution binding assays established that it adopts a ClpS-like fold with a hydrophobic N-degron pocket capable of discriminating N-end rule peptides despite a latch-occluded conformation in the crystal.","evidence":"X-ray crystallography at 2.7 Å with solution peptide-binding assays","pmids":["26701219"],"confidence":"High","gaps":["Physiological N-degron substrates in the parasite not identified","Conformational switching of the latch loop not directly demonstrated in a functional cycle"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Where ClpS acts in the cell was addressed bioinformatically: the presence of an apicoplast targeting peptide indicated apicoplast localization consistent with a role in the organellar Clp machinery.","evidence":"Sequence analysis of apicoplast targeting peptide","pmids":["26701219"],"confidence":"Low","gaps":["Localization inferred from targeting sequence only, not confirmed by imaging or fractionation","Does not establish the timing or stage-specificity of apicoplast import"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"Whether ClpS was functionally required, rather than merely present, was resolved by conditional mutants showing ClpS is essential for apicoplast biogenesis in blood-stage parasites.","evidence":"Conditional inducible genetic knockdown/mutant with apicoplast biogenesis phenotypic readout","pmids":["32482878"],"confidence":"High","gaps":["Does not identify the substrates whose mis-regulation causes the biogenesis defect","Does not distinguish the adaptor step from downstream proteolysis in the essential phenotype"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"How ClpS integrates with the protease was addressed by affinity purification screens placing it within a multi-subunit apicoplast Clp complex containing PfClpP and PfClpC.","evidence":"Multiple affinity purification/mass spectrometry screens","pmids":["32482878"],"confidence":"Medium","gaps":["No reciprocal co-IP or reconstitution to confirm direct interaction","Stoichiometry and architecture of ClpS within the complex not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"The physiological N-degron substrates that ClpS recognizes and delivers to the apicoplast Clp protease, and the mechanism coupling substrate recognition to degradation and apicoplast biogenesis, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No endogenous substrate identified","Direct interaction with PfClpC/PfClpP not reconstituted","Mechanism linking substrate delivery to apicoplast biogenesis unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Apicoplast Clp proteolytic complex (with PfClpP and PfClpC) [#3]"],"partners":["PFCLPP (COMPLEX CO-MEMBER) [#3]","PFCLPC (COMPLEX CO-MEMBER) [#3]"],"other_free_text":["Bacterial ClpS-like fold with a hydrophobic N-degron binding pocket occluded by a conserved surface-loop latch in the crystal but open in solution [#0]","Binds and discriminates peptides mimicking N-end rule substrates [#0]","Essential for apicoplast biogenesis in blood-stage parasites (conditional mutant) [#2]","Apicoplast localization inferred from a targeting peptide, not confirmed by imaging [#1]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"33497624","id":"PMC_33497624","title":"Structure, function, and substrates of Clp AAA+ protease systems in cyanobacteria, plastids, and apicoplasts: A comparative analysis.","date":"2021","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/33497624","citation_count":61,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ClpS","ATP"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32482878","id":"PMC_32482878","title":"Plastid biogenesis in malaria parasites requires the interactions and catalytic activity of the Clp proteolytic system.","date":"2020","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/32482878","citation_count":29,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfClpS"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"26701219","id":"PMC_26701219","title":"Structure of a putative ClpS N-end rule adaptor protein from the malaria pathogen Plasmodium falciparum.","date":"2016","source":"Protein science : a publication of the Protein Society","url":"https://pubmed.ncbi.nlm.nih.gov/26701219","citation_count":24,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ClpS"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":4426,"output_tokens":1066,"usd":0.014634,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5865,"output_tokens":2154,"usd":0.041587,"stage2_stop_reason":"end_turn"},"total_usd":0.056221,"stage1_batch_id":"msgbatch_011BPjN2BL33F8cJXD1r7V7T","stage2_batch_id":"msgbatch_01Qwg6vP7qxkpL6Gsc7tajsb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"Crystal structure of P. falciparum ClpS (PF3D7_1320100) solved at 2.7 Å resolution reveals a hydrophobic N-degron binding pocket occluded by a conserved surface loop acting as a latch; despite the closed conformation in the crystal, solution binding assays show ClpS binds and discriminates peptides mimicking N-end rule substrates.\",\n      \"method\": \"X-ray crystallography (2.7 Å); solution peptide-binding assays\",\n      \"journal\": \"Protein science : a publication of the Protein Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with functional validation by solution binding assay in a single rigorous study\",\n      \"pmids\": [\"26701219\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The presence of an apicoplast targeting peptide in P. falciparum ClpS (PF3D7_1320100) indicates it localizes to the apicoplast, consistent with its predicted function as a substrate adaptor for the apicoplast Clp machinery.\",\n      \"method\": \"Sequence analysis of apicoplast targeting peptide (bioinformatic/structural study)\",\n      \"journal\": \"Protein science : a publication of the Protein Society\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — localization inferred from targeting peptide sequence, not confirmed by direct imaging or fractionation experiment\",\n      \"pmids\": [\"26701219\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Conditional mutants of P. falciparum ClpS (PF3D7_1320100, referred to as PfClpS in this study) demonstrate that ClpS is essential for apicoplast biogenesis in blood-stage parasites.\",\n      \"method\": \"Conditional (inducible) genetic knockdown/mutant with apicoplast biogenesis phenotypic readout\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional null mutant with defined organelle biogenesis phenotype in a rigorous study\",\n      \"pmids\": [\"32482878\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Affinity purification screens identified P. falciparum ClpS (PF3D7_1320100) as part of the apicoplast Clp complex, establishing its membership in a multi-subunit protease complex that includes PfClpP and PfClpC.\",\n      \"method\": \"Multiple affinity purification/mass spectrometry screens\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple independent affinity purification experiments converging on complex membership, but no reciprocal co-IP or reconstitution\",\n      \"pmids\": [\"32482878\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"P. falciparum ClpS (PF3D7_1320100) is an apicoplast-localized N-end rule substrate adaptor that adopts a bacterial ClpS-like fold with a hydrophobic N-degron binding pocket (occluded in the crystal by a surface loop but open in solution), functions as part of the multi-subunit apicoplast Clp proteolytic complex (with PfClpP and PfClpC), and is essential for apicoplast biogenesis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"P. falciparum ClpS (PF3D7_1320100) is a substrate adaptor of the apicoplast Clp proteolytic machinery that is essential for apicoplast biogenesis in blood-stage parasites [#2, #3]. Its 2.7 Å crystal structure reveals a bacterial ClpS-like fold with a hydrophobic N-degron binding pocket; in the crystal this pocket is occluded by a conserved surface loop acting as a latch, yet solution binding assays show that ClpS binds and discriminates peptides mimicking N-end rule substrates, consistent with a role in recognizing and delivering N-degron-bearing substrates for proteolysis [#0]. Affinity purification screens place ClpS within a multi-subunit apicoplast Clp complex that includes PfClpP and PfClpC [#3]. Beyond its membership in this complex, its N-degron recognition activity, and its requirement for apicoplast biogenesis, no further mechanistic detail — including direct identification of its physiological substrates or reciprocal validation of its complex interactions — has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"It was unknown whether Plasmodium ClpS retained the structural machinery to act as an N-end rule substrate adaptor; the crystal structure and solution binding assays established that it adopts a ClpS-like fold with a hydrophobic N-degron pocket capable of discriminating N-end rule peptides despite a latch-occluded conformation in the crystal.\",\n      \"evidence\": \"X-ray crystallography at 2.7 Å with solution peptide-binding assays\",\n      \"pmids\": [\"26701219\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological N-degron substrates in the parasite not identified\", \"Conformational switching of the latch loop not directly demonstrated in a functional cycle\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Where ClpS acts in the cell was addressed bioinformatically: the presence of an apicoplast targeting peptide indicated apicoplast localization consistent with a role in the organellar Clp machinery.\",\n      \"evidence\": \"Sequence analysis of apicoplast targeting peptide\",\n      \"pmids\": [\"26701219\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Localization inferred from targeting sequence only, not confirmed by imaging or fractionation\", \"Does not establish the timing or stage-specificity of apicoplast import\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Whether ClpS was functionally required, rather than merely present, was resolved by conditional mutants showing ClpS is essential for apicoplast biogenesis in blood-stage parasites.\",\n      \"evidence\": \"Conditional inducible genetic knockdown/mutant with apicoplast biogenesis phenotypic readout\",\n      \"pmids\": [\"32482878\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not identify the substrates whose mis-regulation causes the biogenesis defect\", \"Does not distinguish the adaptor step from downstream proteolysis in the essential phenotype\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"How ClpS integrates with the protease was addressed by affinity purification screens placing it within a multi-subunit apicoplast Clp complex containing PfClpP and PfClpC.\",\n      \"evidence\": \"Multiple affinity purification/mass spectrometry screens\",\n      \"pmids\": [\"32482878\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reciprocal co-IP or reconstitution to confirm direct interaction\", \"Stoichiometry and architecture of ClpS within the complex not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The physiological N-degron substrates that ClpS recognizes and delivers to the apicoplast Clp protease, and the mechanism coupling substrate recognition to degradation and apicoplast biogenesis, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No endogenous substrate identified\", \"Direct interaction with PfClpC/PfClpP not reconstituted\", \"Mechanism linking substrate delivery to apicoplast biogenesis unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0030674\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0042277\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020011\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006508\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0071586\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [\n      \"Apicoplast Clp proteolytic complex (with PfClpP and PfClpC) [#3]\"\n    ],\n    \"partners\": [\n      \"PfClpP (complex co-member) [#3]\",\n      \"PfClpC (complex co-member) [#3]\"\n    ],\n    \"other_free_text\": [\n      \"Bacterial ClpS-like fold with a hydrophobic N-degron binding pocket occluded by a conserved surface-loop latch in the crystal but open in solution [#0]\",\n      \"Binds and discriminates peptides mimicking N-end rule substrates [#0]\",\n      \"Essential for apicoplast biogenesis in blood-stage parasites (conditional mutant) [#2]\",\n      \"Apicoplast localization inferred from a targeting peptide, not confirmed by imaging [#1]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1320100","name":null,"product":"ATP-dependent Clp protease adapter protein ClpS","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1418400","name":null,"product":"ATP-dependent Clp protease adapter protein ClpS, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1420700","name":null,"product":"ATP-dependent Clp protease adapter protein ClpS, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"ClpS","evaluation":null}