axonemal B tubule inner sheath

GO:0160112 · Cytoskeleton · Multiprotein complex · Proposed

The microtubule-inner-protein network inside the lumen of the B tubule of the axonemal doublet microtubule. [GO:0160112]

Part of: axonemal microtubule doublet inner sheath (GO:0160110); B axonemal microtubule (GO:0097650)

Taxonomic distribution

NCBITaxon:3055 Chlamydomonas reinhardtii — COMMON: Chlamydomonas axonemal B tubules contain a luminal inner-sheath MIP network within native doublet microtubules. [DOI:10.1016/j.cell.2019.09.030]

NCBITaxon:3055 Chlamydomonas reinhardtii — Green-algal model whose B-tubule luminal MIP densities were resolved in decorated axonemal doublets. [DOI:10.1016/j.cell.2019.09.030]

B-tubule luminal stabilization — The axonemal B tubule inner sheath is a luminal MIP network that helps stabilize the B tubule of the axonemal doublet.
- GO:0160112 GO defines the axonemal B tubule inner sheath as a MIP network inside the B-tubule lumen that helps stabilize the B tubule.
- DOI:10.1016/j.cell.2019.09.030 Ma et al. 2019 resolved interconnected MIP densities inside native Chlamydomonas B tubules.

In Chlamydomonas axonemal doublets, the B-tubule inner sheath is the MIP network inside the B-tubule lumen and is part of the doublet inner sheath.

Subject	Predicate	Object	Evidence
axonemal B tubule inner sheath	is part of	axonemal microtubule doublet inner sheath	`GO:0160112` GO places the axonemal B tubule inner sheath within the axonemal microtubule doublet inner sheath.
axonemal B tubule inner sheath	occupies lumen of	B axonemal microtubule	`GO:0160112` GO defines the B-tubule inner sheath as a MIP network inside the B-tubule lumen.
axonemal B tubule inner sheath	stabilizes	B axonemal microtubule	`GO:0160112` GO defines the B-tubule inner sheath by its B-tubule-stabilizing function.

CURATION_TODO (OPEN): Resolve exact conserved B-tubule MIP family groundings, positions and copy numbers for the axonemal B tubule inner sheath. GO exactly identifies the B-tubule inner sheath, but this pass does not assign individual B-lumen MIP families, positions or copy numbers.
INTERPRETATION (OPEN): Reconcile the GO:0160112 typed A-tubule parthood relation with its B-lumen definition and primary structural evidence. On 2026-10-11, QuickGO, the typed OLS part_of endpoint and AmiGO expose GO:0097649 A axonemal microtubule for GO:0160112, while the term definition locates the sheath in the B lumen. Ma et al. 2019 independently supports B-lumen MIP networks. The native GO:0097650 parthood is retained on that biological evidence; the conflicting ontology relationship is not copied or claimed to be corrected.

GO:0160112 Gene Ontology cellular-component term for the axonemal B tubule inner sheath.
GO:0160110 Gene Ontology places the axonemal B tubule inner sheath within the axonemal microtubule doublet inner sheath.
GO:0097650 GO identifies the B axonemal microtubule. B-lumen containment is supported by the GO:0160112 textual definition and Ma et al. 2019, not by its current typed GO parthood edge, which names the A tubule.
DOI:10.1016/j.cell.2019.09.030 Ma et al. 2019, 'Structure of the Decorated Ciliary Doublet Microtubule', Cell. The luminal-coating and MIP-network Results support the B-lumen network and its B-tubule containment; this evidence is retained separately from the conflicting GO relationship.

2026-09-23T18:29:30Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-23T18:30:46Z codex · EXPANDED_RECORD — Added inner-sheath and B-tubule parthood, Chlamydomonas scope, GO and DOI evidence, a nonmechanistic B-tubule inner-sheath graph, and a B-tubule MIP-family TODO.
2026-10-11T08:09:49Z codex · ADDRESS_SAVED_REVIEW — Addressed #2194: Corrected B-sheath ontology attribution and retained the current source discrepancy explicitly without changing primary-supported B-tubule containment or the existing MIP-family TODO.