flagellar pocket

GO:0020016 · Membrane organelle · Subcellular region · Proposed

Invagination of the plasma membrane from which a flagellum protrudes. [GO:0020016]

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

Components

Taxonomic distribution

• NCBITaxon:5691 Trypanosoma brucei — COMMON: T. brucei cells have a single flagellar pocket that has been reconstructed by electron tomography and used as a model for trypanosomatid endocytosis and exocytosis. [DOI:10.1242/jcs.045740]

Canonical examples

• NCBITaxon:5691 Trypanosoma brucei — African trypanosome in which flagellar-pocket membrane domains, electron-tomographic architecture and BILBO1-dependent biogenesis have been studied. [DOI:10.1242/jcs.045740]

Functions

• endocytic and exocytic gateway — The flagellar pocket concentrates endocytosis and exocytosis at the site where the flagellum exits the trypanosome cell body.
  • DOI:10.1038/nrmicro2221 Field and Carrington 2009 reviewed the trypanosome flagellar pocket as the dominant site of endo- and exocytosis.
  • DOI:10.1016/j.pt.2020.11.005 Halliday and Sunter 2021 review how the trypanosomatid flagellar pocket couples pocket structure to trafficking functions.
• flagellum exit-site organization — The pocket organizes the membrane invagination and neck through which the eukaryotic flagellum emerges from the cell body.
  • DOI:10.1242/jcs.045740 Lacomble et al. 2009 reconstructed the T. brucei flagellar pocket and associated cytoskeleton by electron microscope tomography.

Mechanism graphs

Flagellar pocket boundaries organize surface traffic (FUNCTION)

The flagellar pocket membrane forms a specialized surface invagination whose neck is marked by the ciliary pocket collar, concentrating endocytic and exocytic traffic at the base of the flagellum.

Discussions

• CURATION_TODO (OPEN): Resolve the hook complex, microtubule quartet, flagellum attachment zone filament and flagellar-pocket membrane proteins before expanding the flagellar-pocket boundary graph. Electron-tomographic and proteomic studies define several cytoskeletal features around the pocket, but this first record curates only the membrane and the already grounded ciliary pocket collar.

Evidence

• DOI:10.1038/nrmicro2221 Field and Carrington 2009, The trypanosome flagellar pocket, Nature Reviews Microbiology.
• DOI:10.1242/jcs.045740 Lacomble et al. 2009, Three-dimensional cellular architecture of the flagellar pocket and associated cytoskeleton in trypanosomes revealed by electron microscope tomography, Journal of Cell Science.
• DOI:10.1073/pnas.0909289106 Gadelha et al. 2009, Membrane domains and flagellar pocket boundaries are influenced by the cytoskeleton in African trypanosomes, Proceedings of the National Academy of Sciences.
• DOI:10.1016/j.pt.2020.11.005 Halliday and Sunter 2021, Trypanosomatid Flagellar Pocket from Structure to Function, Trends in Parasitology.
• DOI:10.1371/journal.pbio.0060105 Bonhivers et al. 2008, Biogenesis of the trypanosome endo-exocytotic organelle is cytoskeleton mediated, PLOS Biology.

Curation history

• 2026-09-10T12:13:38Z claude · CREATED_RECORD — Scaffolded by scripts/new_record.py
• 2026-09-10T12:14:11Z claude · EXPANDED_RECORD — Added FP synonymy, ciliary pocket membrane and ciliary pocket collar components, Trypanosoma brucei scope, endocytic and exocytic gateway functions, flagellar pocket literature evidence, a nonmechanistic boundary/traffic graph, and a cytoskeletal-boundary curation TODO.
• 2026-09-10T12:20:26Z claude · ADDRESSED_PR_REVIEW — Addressed PR #362 review issues #363 and #364 by removing the ambiguous FP synonym and retargeting the ciliary pocket collar graph edge to the flagellar pocket neck.

Source: data/structures/membrane_organelle/flagellar_pocket.yaml