ciliary centrin arm

GO:0120269 · Cytoskeleton · Multiprotein complex · Proposed

A rod-shaped protein complex containing Centrin4 protein that flanks the flagellum attachment zone (FAZ) filament and the quartet microtubules. [GO:0120269]

Part of: flagellar pocket (GO:0020016)

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
Centrin4 ciliary centrin arm protein	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	TbCentrin4		UNKNOWN	Centrin-family marker of the rod-shaped ciliary centrin arm in the trypanosome hook-complex/bilobe region. `GO:0120269` GO:0120269 defines the ciliary centrin arm as a rod-shaped protein complex containing Centrin4. `DOI:10.3390/cells4040726` Morriswood 2015 distinguished the TbCentrin4-positive centrin arm from the TbMORN1-positive hook complex in T. brucei, while discussing their historical grouping as the bilobe and unresolved physical boundaries.

Taxonomic distribution

NCBITaxon:5691 Trypanosoma brucei — COMMON: The ciliary centrin arm has been studied as a Centrin4-positive rod alongside the trypanosome hook complex, neighboring the microtubule quartet and FAZ filament. [DOI:10.1242/jcs.230581]

Canonical examples

NCBITaxon:5691 Trypanosoma brucei — Trypanosome model in which BOH1 and hook-complex proteins have been connected to ciliary centrin arm assembly and flagellum inheritance. [DOI:10.1074/jbc.RA120.014237]

Functions

hook-complex and FAZ filament flanking — The ciliary centrin arm flanks the flagellum attachment zone filament and the microtubule quartet in the T. brucei flagellar pocket-associated cytoskeleton.
- GO:0120269 The GO definition places the ciliary centrin arm beside the FAZ filament and quartet microtubules.
- DOI:10.3390/cells4040726 Morriswood 2015 described the Centrin4-positive centrin arm alongside the MORN1-positive hook complex, distinguishing these terms within the historical trypanosome bilobe region.
flagellum inheritance support — Hook-complex integrity and ciliary centrin arm assembly support flagellum inheritance in T. brucei.
- DOI:10.1074/jbc.RA120.014237 Pham et al. 2020 connected maintenance of hook-complex integrity and centrin arm assembly to flagellum inheritance in T. brucei.

Discussions

CURATION_TODO (OPEN): Resolve additional ciliary centrin arm and hook-complex proteins before expanding the component list. The ciliary centrin arm is a Centrin4-containing complex, but this first record does not assert BOH1 or other hook-complex proteins as arm constituents until source-neutral families and their structural boundaries are curated.
CURATION_TODO (OPEN): Keep the ciliary centrin arm separated from the complete bilobe or hook complex in future graph curation. GO:0120269 denotes the rod-shaped Centrin4 arm, whereas GO:0120120 denotes the larger bilobe structure that links the ciliary pocket collar and the flagellum attachment zone.

Evidence

DOI:10.3390/cells4040726 Morriswood 2015, Form, Fabric, and Function of a Flagellum-Associated Cytoskeletal Structure, Cells.
DOI:10.1242/jcs.230581 Pham et al. 2019, BOH1 cooperates with Polo-like kinase to regulate flagellum inheritance and cytokinesis initiation in Trypanosoma brucei, Journal of Cell Science.
DOI:10.1074/jbc.RA120.014237 Pham, Hu and Li 2020, Maintenance of hook complex integrity and centrin arm assembly facilitates flagellum inheritance in Trypanosoma brucei, Journal of Biological Chemistry.

Curation history

2026-10-03T04:29:00Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-03T04:29:46Z codex · EXPANDED_RECORD — Added intracellular-protein-complex parentage and ciliary-pocket parthood, curated Centrin4 as a reviewed-label-only constituent, added Trypanosoma brucei scope, hook/FAZ and flagellum-inheritance functions, core literature evidence, and open component-boundary discussions.
2026-10-11T23:33:45Z codex · ADDRESS_SAVED_REVIEW — Addressed #2266: distinguished centrin-arm and hook-complex terminology in assertion-local source notes and occurrence wording.

Source: data/structures/cytoskeleton/ciliary_centrin_arm.yaml