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The N-terminal loops of adjacent sheath initiators adopt different conformations to accommodate the symmetry mismatch between the baseplate wedge and hub.","domain_architectures":7,"interpro_id":"IPR020288","known_evidence_count":null,"matches":2400,"name":"Contractile injection system sheath initiator","partial_evidence_count":null,"pfam_id":"PF10934","proteins":2400,"proteomes":1845,"short_name":"Sheath_initiator","source_url":"https://www.ebi.ac.uk/interpro/api/entry/pfam/PF10934","structures":26,"taxa":3585,"unknown_status":"EX_DUF"},"inputs":{"cross_mech":"cross-mech-duf-examples-2026-10-10","members":"pfam-uniprot-uniref90-2026-10-07","protein_examples":"duf-protein-examples-2026-10-13","worklist":"interpro-pfam-duf-2026-10-10"},"members":[],"metadata":{"curation_status":"SEEDED","local_source":"source/data/families/PF10934.yaml","record":{"characterization_status":"UNSCORED","counters":{"alphafold_models":1129,"domain_architectures":7,"matches":2400,"proteins":2400,"proteomes":1845,"structures":26,"taxa":3585},"curation_status":"SEEDED","description":"This entry represents the sheath initiator protein found in contractile injection systems like diffocins, pyocins, and phage tail-like particles. The sheath initiator acts as an intermediate between the baseplate triplex and the first layer of the sheath, and between the tube tail and hub. It has a critical role in transmitting contraction signals from the baseplate wedge to the sheath through the N-terminal domain which binds to the core bundle of the triplex, while the C-terminal beta-hairpin interacts with two sheath proteins on the first layer by forming a conserved handshake interface. 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