All families / PF11439
PF11439: T3SchapCesA
Type III secretion system filament chaperone CesA
- Curation status
- SEEDED
- Seed status
- EX DUF
- Characterization
- UNSCORED
Grounding
PF11439: Type III secretion system filament chaperone CesA
IPR021545: integrated entry for Type III secretion system filament chaperone CesA
Source 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.
Evidence and references
Source descriptions and links are provenance, not independent functional validation.
Evidence counts: not scored.
Curated functional assertions
No curated functional assertions supplied.
Protein sequence examples
No sibling protein candidate in the scanned commits.
Pfam membership is not functional evidence. Whole-protein sequences do not establish domain boundaries. A coverage gap here is not absence from UniProt.
Sequences and metadata: UniProt Consortium, CC BY 4.0.
Domain matches
No residue-level domain match evidence is available in this build. Structure and AlphaFold counters do not supply coordinates or establish function.
Snapshot counters
- proteins
- 8
- matches
- 8
- proteomes
- 5
- taxa
- 24
- structures
- 3
- alphafold models
- 6
- domain architectures
- 1
Classification basis
pfam previous unknown name
No scoring reasons supplied.
Related Mech records
This family joined the worklist after the frozen cross-Mech scan, so other Mechs were not searched for it. Missing links here are not evidence that other Mechs lack it; rows shown come from mentions of a former DUF/UPF name.
No cross-Mech examples are present in the supplied snapshot.
Curation history and reviews
No retained curation events supplied.
No retained review supplied.
Record source
Status and evidence
- Seed status
- A name-based classification of frozen InterPro/Pfam metadata. UNKNOWN CANDIDATE means the metadata explicitly says the function is unknown. KNOWN HISTORICAL DUF means a DUF name matched without that wording; this heuristic is not proof of a known function and does not establish experimental characterization. EX DUF means Pfam renamed the family away from a DUF/UPF name, as recorded in Pfam's previous identifiers; a rename usually follows published work on some members but is naming history, not proof of function for every member. Some EX DUF families' current names or descriptions still say the function is unknown; their classification basis lists this, and scoring does not treat them as characterized. FALSE POSITIVE TEXT HIT means the naming rules did not match.
- Characterization
- A separate evidence-scoring result. UNSCORED means no score has been calculated; it is not evidence that the family lacks a known function. Missing scores are not negative evidence. PARTIALLY CHARACTERIZED has partial support; KNOWN HISTORICAL DUF can inherit the seed label or reflect a known-function signal. Neither label implies experimental validation.
- Evidence counts
- Source-specific signals, not unique proteins, publications, or confidence scores. Known counts Rhea reactions and experimentally supported GO molecular-function annotations. Partial counts functional/domain assignments. Context counts structural, environmental, orthology, interaction and neighborhood signals; context alone does not assign function. Repeated annotations may not be independent.
- Curation status
- Reported separately from seed classification and characterization. SNAPSHOT ONLY means no curated metadata was supplied for this build. SEEDED denotes a source-derived record, not an expert-reviewed functional claim.
- Missing counts
- Not available means the source did not supply that counter. A zero is a reported count. Not scored means evidence counts are unavailable.