id: Pfam:PF10934
pfam_id: PF10934
name: Contractile injection system sheath initiator
short_name: Sheath_initiator
seed_status: EX_DUF
characterization_status: UNSCORED
curation_status: SEEDED
source_url: https://www.ebi.ac.uk/interpro/api/entry/pfam/PF10934
counters:
  proteins: 2400
  matches: 2400
  proteomes: 1845
  taxa: 3585
  structures: 26
  alphafold_models: 1129
  domain_architectures: 7
provenance:
  snapshot_id: interpro-pfam-duf-2026-10-10
  path: data/worklists/interpro-pfam-duf-2026-10-10.json
  sha256: 17fb625876c9326ed284263a47bcd84e0d7844a31c040dc06cd2260c36f1c383
  generated_at: '2026-10-10T07:44:21.614711Z'
  source_url: https://www.ebi.ac.uk/interpro/api/entry/pfam/
interpro_id: InterPro:IPR020288
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. The
  N-terminal loops of adjacent sheath initiators adopt different conformations to accommodate the symmetry
  mismatch between the baseplate wedge and hub.