{"id":"59997dee-4652-5f00-be89-9a07d32bcbf1","stable_key":"aaa7baba-8689-56ab-ba1e-b71542bcb8e9:iodine-syn-tpo-heme-structure","predicate":"binds","statement":"Cryo-EM structures of the human TPO extracellular domain resolve heme at the peroxidase active site.","claim_class":"identity","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"d088a297-b4aa-54e1-b8fe-ad4740cb72df","mechanism_event_label":"TPO contains an iron-bearing heme group at its catalytic center.","subject":{"id":"77cde6e6-d7fa-5700-8601-1bf720b6000f","slug":"human-tpo-ectodomain-1-839","display_name":"Human TPO ectodomain residues 1–839","entity_type_key":"protein_state"},"object":{"id":"2e1f7e0a-8b54-5ea3-9d34-01e7167f9097","slug":"heme","display_name":"Heme","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"d088a297-b4aa-54e1-b8fe-ad4740cb72df","stable_key":"aaa7baba-8689-56ab-ba1e-b71542bcb8e9:iodine-syn-tpo-heme-structure-event","event_type":"biochemical_relationship","label":"TPO contains an iron-bearing heme group at its catalytic center.","description":"Cryo-EM structures of the human TPO extracellular domain resolve heme at the peroxidase active site.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"d5e001d7-78aa-5636-8891-07672ef87e0f","slug":"tpo","display_name":"Human thyroid peroxidase","entity_type_key":"protein"},"role":"full_length_parent","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"89bcaf42-b4ab-5760-8c2e-44eace10cee0","slug":"iron","display_name":"Iron","entity_type_key":"nutrient_element"},"role":"heme_metal","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"77cde6e6-d7fa-5700-8601-1bf720b6000f","slug":"human-tpo-ectodomain-1-839","display_name":"Human TPO ectodomain residues 1–839","entity_type_key":"protein_state"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"2e1f7e0a-8b54-5ea3-9d34-01e7167f9097","slug":"heme","display_name":"Heme","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"true","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_span","value_text":"{\"source_cache\": \"artifacts/iodine-synthesis-sources/36537574.txt\", \"start_char\": 17835, \"end_char\": 18855, \"text_sha256\": \"6771d21482631bf712dfa882f1d08e4f40e02507211c65a60c7ef47f0d02e5d4\", \"text_characters\": 1020, \"note\": \"Exact publisher passage retained in the cited local source cache; locator and digest supplied here.\"}","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Cryo-EM of recombinant human TPO extracellular domain with antibody fragments","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Human TPO residues 1–839 expressed in High Five insect cells and bound to 2G4 or 4F5 antibody fragments.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"A structural observation; no selenium catalytic requirement or dietary iron dose is demonstrated.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Iodine research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"iodine","display_name":"Iodine","entity_type_key":"nutrient_element"}},{"dimension":"organism","value_text":"Homo sapiens protein; Trichoplusia ni expression cells","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"TPO contains an iron-bearing heme group at its catalytic center.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[iodine-syn-tpo2023] Cryo-electron microscopy structures of human thyroid peroxidase (TPO) in complex with TPO antibodies. (2023). https://pubmed.ncbi.nlm.nih.gov/36537574/ DOI: 10.1530/jme-22-0149","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Purified extracellular-domain antibody complexes","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"16b5900a-08a1-5f20-8282-7c05f75892e7","evidence_kind":"source_excerpt","locator":"Lines 604-616","start_line":604,"end_line":616,"excerpt":"### iodine-syn-tpo-heme-structure\nCryo-EM structures of the human TPO extracellular domain resolve heme at the peroxidase active site.\nCondition category: normal\nnutrient_topic: Iodine research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: TPO contains an iron-bearing heme group at its catalytic center.\norganism: Homo sapiens protein; Trichoplusia ni expression cells\ntissue_or_cell_type: Purified extracellular-domain antibody complexes\nexperimental_model: Cryo-EM of recombinant human TPO extracellular domain with antibody fragments\nlimitations: A structural observation; no selenium catalytic requirement or dietary iron dose is demonstrated.\nexposure: Human TPO residues 1–839 expressed in High Five insect cells and bound to 2G4 or 4F5 antibody fragments.\ncross_nutrient: true\nevidence_span: {\"source_cache\": \"artifacts/iodine-synthesis-sources/36537574.txt\", \"start_char\": 17835, \"end_char\": 18855, \"text_sha256\": \"6771d21482631bf712dfa882f1d08e4f40e02507211c65a60c7ef47f0d02e5d4\", \"text_characters\": 1020, \"note\": \"Exact publisher passage retained in the cited local source cache; locator and digest supplied here.\"}\n[iodine-syn-tpo2023] Cryo-electron microscopy structures of human thyroid peroxidase (TPO) in complex with TPO antibodies. (2023). https://pubmed.ncbi.nlm.nih.gov/36537574/ DOI: 10.1530/jme-22-0149","model_system":"Cryo-EM of recombinant human TPO extracellular domain with antibody fragments","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [iodine-syn-tpo2023] Cryo-electron microscopy structures of human thyroid peroxidase (TPO) in complex with TPO antibodies. (2023). https://pubmed.ncbi.nlm.nih.gov/36537574/ DOI: 10.1530/jme-22-0149","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"76da623d-a34a-5a5c-a942-d7571a85c486","stable_key":"import-aaa7baba-8689-56ab-ba1e-b71542bcb8e9","title":"Iodine: thyroid hormone production, deficiency, excess and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. 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