axonemal microtubule doublet ribbon

GO:0160115 · Cytoskeleton · Filament · Proposed

A three-protofilament ribbon formed by A-tubule protofilaments A11, A12 and A13 plus associated microtubule inner proteins that separates the A- and B-tubule lumens within an axonemal doublet microtubule. [GO:0160115]

Part of: axonemal doublet microtubule (GO:0097545)

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
A11-A13 ribbon tubulins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			ESSENTIAL	Alpha- and beta-tubulin subunits that form protofilaments A11, A12 and A13 of the axonemal A-tubule ribbon. `GO:0160115` GO defines the axonemal doublet ribbon as A-tubule protofilaments A11, A12 and A13 plus associated MIPs. `DOI:10.1242/jcs.20.2.405` Linck 1976 biochemically isolated detergent-resistant flagellar doublet ribbons with three protofilaments and minor non-tubulin proteins.
ribbon-associated microtubule inner proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Microtubule inner proteins associated with the axonemal doublet ribbon and its periodic accessory densities. `GO:0160115` GO includes associated MIPs in the axonemal microtubule doublet ribbon boundary. `DOI:10.1074/jbc.M210751200` Ikeda et al. 2003 identified Chlamydomonas Rib72 as a conserved protein associated with the flagellar A-microtubule ribbon compartment. `DOI:10.1002/bies.201700209` Ichikawa and Bui 2018 reviewed MIP densities, including MIPs associated with the A-tubule ribbon region of axonemal doublets.

Taxonomic distribution

NCBITaxon:3055 Chlamydomonas reinhardtii — COMMON: Chlamydomonas flagellar A-microtubules contain a ribbon compartment marked by the conserved Rib72 protein. [DOI:10.1074/jbc.M210751200]

Canonical examples

NCBITaxon:3055 Chlamydomonas reinhardtii — Green-algal model used to identify Rib72 as a conserved axonemal A-microtubule ribbon-compartment protein. [DOI:10.1074/jbc.M210751200]

Functions

A-tubule ribbon stabilization — The A11-A13 protofilament ribbon and its associated MIPs form a stable axonemal doublet substructure that separates the A- and B-tubule lumens.
- GO:0160115 GO defines the ribbon by A11-A13 protofilaments and associated MIPs that stabilize those protofilaments within the axonemal doublet.
- DOI:10.1242/jcs.20.2.405 Linck 1976 found that flagellar doublet extraction leaves stable ribbons of three protofilaments with 16-nm axial repeats.

Mechanism graphs

Tubulin and MIPs form the A-tubule ribbon (FUNCTION)

The A11-A13 tubulin protofilaments and ribbon-associated MIPs form a stable ribbon along the A-tubule side of the axonemal doublet.

Subject	Predicate	Object	Evidence
A11-A13 ribbon tubulins	form	axonemal microtubule doublet ribbon	`GO:0160115` GO identifies A11, A12 and A13 as the ribbon protofilaments.
ribbon-associated microtubule inner proteins	bind	axonemal microtubule doublet ribbon	`DOI:10.1074/jbc.M210751200` Ikeda et al. 2003 localized Chlamydomonas Rib72 to the flagellar A-microtubule ribbon compartment. `DOI:10.1002/bies.201700209` Ichikawa and Bui 2018 reviewed MIPs that decorate the stable axonemal doublet ribbon.
axonemal microtubule doublet ribbon	is part of	axonemal doublet microtubule	`GO:0160115` GO places the axonemal microtubule doublet ribbon within the axonemal doublet microtubule.
axonemal microtubule doublet ribbon	stabilizes	axonemal doublet microtubule	`GO:0160115` GO defines the ribbon as A11-A13 plus associated MIPs that stabilize those protofilaments within the axonemal doublet. `DOI:10.1242/jcs.20.2.405` Linck 1976 found that biochemical extraction of flagellar doublets leaves stable three-protofilament ribbons with 16-nm axial repeats.

Discussions

CURATION_TODO (OPEN): Resolve exact Rib72 and other axonemal doublet ribbon MIP family groundings, memberships and copy numbers. Linck 1976 biochemically identified stable three-protofilament ribbons and Ikeda et al. 2003 localized Rib72 to the Chlamydomonas ribbon compartment, but this pass did not verify source-neutral CURIEs for ribbon-associated MIP families.

Evidence

GO:0160115 Gene Ontology cellular-component term for the axonemal doublet ribbon.
GO:0097545 GO places the axonemal microtubule doublet ribbon within the axonemal doublet microtubule.
DOI:10.1242/jcs.20.2.405 Linck 1976, 'Flagellar doublet microtubules: fractionation of minor components and alpha-tubulin from specific regions of the A-tubule', Journal of Cell Science.
DOI:10.1074/jbc.M210751200 Ikeda et al. 2003, 'Rib72, a conserved protein associated with the ribbon compartment of flagellar A-microtubules and potentially involved in the linkage between outer doublet microtubules', Journal of Biological Chemistry.
DOI:10.1002/bies.201700209 Ichikawa and Bui 2018, 'Microtubule Inner Proteins: A Meshwork of Luminal Proteins Stabilizing the Doublet Microtubule', BioEssays.

Curation history

2026-09-23T13:21:56Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-23T13:22:41Z codex · EXPANDED_RECORD — Added doublet parthood, label-only ribbon tubulin and MIP components, Chlamydomonas scope, A-tubule ribbon stabilization function, GO and DOI evidence, a nonmechanistic ribbon graph, and a ribbon MIP-grounding TODO.
2026-09-23T13:34:46Z codex · ADDRESSED_REVIEW — Addressed PR #1398 review issue #1399 by adding an evidence-backed stabilizes edge to the axonemal doublet ribbon graph.

Source: data/structures/cytoskeleton/axonemal_microtubule_doublet_ribbon.yaml