type IV pilus

GO:0044096 · Appendage · Appendage · Proposed

A dynamic bacterial surface filament assembled from type IV pilins by an inner-membrane ATPase machinery. Reversible extension and retraction can generate force for twitching motility, adhesion, surface sensing, and DNA uptake. [DOI:10.1038/nrmicro.2017.40]

Synonyms: type 4 pilus; T4P

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
major type IV pilin	Protein	part of				ESSENTIAL	Polymerizes into the extracellular pilus filament. `DOI:10.1038/nrmicro.2017.40` Hospenthal et al. review T4P filament architecture.

Taxonomic distribution

NCBITaxon:2 Bacteria — VARIABLE: Widely distributed but absent from many lineages and strains. [DOI:10.1038/nrmicro.2017.40]

Canonical examples

NCBITaxon:287 Pseudomonas aeruginosa — Canonical retractile T4P model for twitching motility. [DOI:10.1038/nrmicro.2017.40]
NCBITaxon:264462 Bdellovibrio bacteriovorus HD100 — Attack-phase cells in the primary cryo-ET study include manually annotated type IV pili. [DOI:10.1038/s41564-023-01401-2]

Functions

type IV pilus-dependent motility GO:0043107 — Repeated extension, surface attachment, and retraction pull the cell across a surface.
- DOI:10.1038/nrmicro.2017.40 T4P dynamics generate motility and adhesion forces.

Mechanism graphs

PilB and PilT drive a type IVa pilus extension-retraction cycle (FUNCTION)

The extension ATPase assembles pilin subunits into the extracellular filament, and the retraction ATPase pulls an attached filament back through the envelope. Surface-attached retraction generates the force used for twitching motility.

Subject	Predicate	Object	Evidence
PilB-family extension ATPase	extends	type IV pilus	`DOI:10.1038/nrmicro.2017.40` Hospenthal, Costa and Waksman 2017 review the PilB-family ATPase as the motor that extends Gram-negative type IV pili.
major type IV pilin	polymerizes into	type IV pilus	`DOI:10.1038/nrmicro.2017.40` Hospenthal, Costa and Waksman 2017 describe T4P fibres as polymers of pilin subunits assembled by the biogenesis machinery.
type IV pilus	reaches	surface-bound type IV pilus	`DOI:10.1073/pnas.121171698` Skerker and Berg 2001 directly observed Pseudomonas aeruginosa type IV pili extending, attaching at their distal ends and retracting.
PilT-family retraction ATPase	retracts	surface-bound type IV pilus	`DOI:10.1038/35024105` Merz, So and Sheetz 2000 measured Neisseria gonorrhoeae pilus retraction and showed that force generation and motility require PilT.
surface-bound type IV pilus	pulls cell during	type IV pilus-dependent motility	`DOI:10.1038/35024105` Merz, So and Sheetz 2000 used laser tweezers to show that T4P filaments retract with enough force to move cells. `DOI:10.1073/pnas.121171698` Skerker and Berg 2001 directly observed Pseudomonas aeruginosa pili alternating extension and retraction during surface motility.

Discussions

CURATION_TODO (RESOLVED): Keep PilB and PilT in the mechanism graph rather than the filament constituent table. The cited review distinguishes the pilin filament from the cytoplasmic PilB/PilT motor subcomplex and its PilC platform. Motor activity is required for extension/retraction in the described type IVa systems but does not make either motor a filament constituent. Keeping motors as external graph nodes avoids assigning filament-formation essentiality to nonconstituents.
CURATION_TODO (OPEN): Resolve exact family groundings for the pilins represented by this broad type IV filament record. The component is the major type IV pilin class. An exact family accession has not been verified for the full subtype scope; do not substitute a broader type-IV-filament or secretion-system domain match.

Datasets

Bdellovibrio attack-phase (CryoETDataPortal:10155) · CRYOET_DATA_PORTAL · STRUCTURAL_IMAGING
Organism: NCBITaxon:264462 Bdellovibrio bacteriovorus HD100 · Platform: cryo-electron tomography
Run 7978 annotation 30707 identifies 8 GO:0044096 (type IV pilus) objects.
CryoET Data Portal dataset 10155; canary run 7978 (ycw2012-11-14-17), one of 105 portal runs; annotation 30707: method_type=manual, annotation_method=manual labeling., annotation_software=IMOD, ground_truth_status=true, is_curator_recommended=true, released 2024-06-03T00:00:00+00:00; deposited 2023-10-01T00:00:00+00:00; released 2023-12-01T00:00:00+00:00; last modified 2023-12-01T00:00:00+00:00. Public portal submissions are CC0 (https://cryoetdataportal.czscience.com/data-submission-policy). Metadata-only ingest: no tomogram or annotation volume was requested, downloaded or hosted.
- DOI:10.1038/s41564-023-01401-2

Evidence

DOI:10.1038/nrmicro.2017.40 A comprehensive guide to pilus biogenesis in Gram-negative bacteria.

Curation history

2026-08-30T19:30:00Z codex · CREATED_RECORD — Added as a literature-backed foundational seed. Identity checked against the 2026-07-01 Gene Ontology release; requires human review.
2026-08-30T20:30:00Z codex · CORRECTED_GROUNDING — Corrected the type IV pilus motility grounding from GO:0009290 (DNA import during transformation) to current GO:0043107 (type IV pilus-dependent motility), verified in QuickGO.
2026-08-31T06:12:34Z claude · SET_COMPONENT_ROLE — component_role became required (#77) so the constituent/machinery distinction is machine-readable rather than prose. Set per component; ASSOCIATED_MACHINERY only where the protein acts on the already-assembled structure.
2026-09-02T06:21:09Z codex · ADD_CANONICAL_EXAMPLE — Added the publication-backed Bdellovibrio bacteriovorus HD100 strain as a canonical type-IV-pilus example before CryoET dataset ingestion.
2026-09-02T06:29:03Z cryoet_data_portal · ADD_STRUCTURAL_DATASET — Added CryoET Data Portal dataset 10155 after exact GraphQL resolution of run 7978 and annotation 30707; required the record's pre-existing exact NCBI taxon and exact GO identity, preserved annotation quality metadata, and stored no imaging volumes.
2026-09-04T00:58:09Z codex · ADD_CAUSAL_GRAPH — Added a DOI-backed FUNCTION graph for the PilB/PilT extension-retraction cycle that assembles type IV pili and pulls surface-bound cells during twitching motility.
2026-10-11T06:33:24Z codex · ADDRESS_SAVED_REVIEW — Addressed #2184: Removed cytoplasmic motor constituent rows, retained their evidenced external graph nodes, and scoped the separate-motor mechanism to type IVa systems.

Source: data/structures/appendage/type_iv_pilus.yaml