id: Pfam:PF11439
pfam_id: PF11439
name: Type III secretion system filament chaperone CesA
short_name: T3SchapCesA
seed_status: EX_DUF
characterization_status: UNSCORED
curation_status: SEEDED
source_url: https://www.ebi.ac.uk/interpro/api/entry/pfam/PF11439
counters:
  proteins: 8
  matches: 8
  proteomes: 5
  taxa: 24
  structures: 3
  alphafold_models: 6
  domain_architectures: 1
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:IPR021545
description: This family represents a chaperone protein for the type III secretion system - TTSS - translocon
  protein EspA, to prevent the latter's self-polymerisation. The TTSS is a highly specialised bacterial
  protein secretory pathway, similar in many ways to the flagellar system, that is essential for the pathogenesis
  of many Gram-negative bacteria. The twenty or so proteins making up the TTSS apparatus, referred to
  as the needle complex, allow the injection of virulence proteins (known as effectors) directly into
  the cytoplasm of the eukaryotic host cells they infect; however, the injection process itself is mediated
  by a subset of extracellular proteins that are secreted by the needle complex to the bacterial surface
  and assembled into the type III translocon - EspA. EspB and EspD. EspA polymerises into an extracellular
  filament, and, as with other fibrous proteins, is apt to undergo massive polymerisation when overexpressed.
  CesA is the secretion chaperone protein that binds to EspA. CesA is dimeric and helical, and it traps
  EspA in a monomeric state and inhibits its polymerisation.