radial spoke stalk

GO:0001536 · Cytoskeleton · Multiprotein complex · Proposed

Protein complex forming the elongated portion of the radial spoke between the base which binds to the A-tubule of each microtubule outer doublet and the neck which connects to the spoke head within the ciliary or flagellum axoneme. [GO:0001536]

Part of: radial spoke (GO:0001534)

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
radial spoke stalk proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Protein constituents of the elongated stalk subcomplex that links the A-tubule-binding base to the radial-spoke neck. `GO:0001536` GO:0001536 defines the radial spoke stalk as a protein complex forming the elongated radial-spoke portion between the A-tubule-binding base and the neck. `DOI:10.1242/jcs.245233` Poghosyan et al. 2020 refined the Chlamydomonas radial-spoke architecture and assigned proteins to the stalk region.

Taxonomic distribution

NCBITaxon:3055 Chlamydomonas reinhardtii — COMMON: Chlamydomonas flagellar axonemes carry radial spokes with elongated stalk subcomplexes resolved by cryo-EM. [DOI:10.1242/jcs.245233]

Canonical examples

NCBITaxon:3055 Chlamydomonas reinhardtii — Green-algal model whose radial-spoke stalks connect the A-tubule-proximal radial-spoke base to the neck in 9+2 flagellar axonemes. [DOI:10.1126/science.1128618]

Functions

radial spoke stalk outer-doublet linkage — The radial spoke stalk forms the elongated portion of each radial spoke between its A-tubule-binding base and the neck that connects to the head.
- GO:0001536 GO:0001536 defines the stalk by its position between the A-tubule-binding radial-spoke base and the neck.
- DOI:10.1242/jcs.245233 Poghosyan et al. 2020 describe the Chlamydomonas radial spoke as a complex in the ciliary motility transducer apparatus and assign stalk-region proteins.

Mechanism graphs

Radial-spoke stalk topology (FUNCTION)

Radial-spoke-stalk proteins form the elongated radial-spoke subcomplex between the outer-doublet-associated base and the neck.

Subject	Predicate	Object	Evidence
radial spoke stalk proteins	contribute to	radial spoke stalk	`GO:0001536` GO:0001536 identifies the radial spoke stalk as a protein complex.
radial spoke stalk	is part of	radial spoke	`GO:0001536` GO:0001536 places the radial spoke stalk as part of the radial spoke.
radial spoke stalk	connects to	radial spoke base	`GO:0001536` GO:0001536 defines the stalk as the elongated radial-spoke portion between the A-tubule-binding base and the neck.
radial spoke stalk	connects to	radial spoke neck	`GO:0001536` GO:0001536 places the stalk between the radial-spoke base and the neck.

Discussions

INTERPRETATION (RESOLVED): Keep the radial spoke stalk distinct from the whole radial spoke and adjacent head and neck subcomplexes. GO:0001536 denotes the elongated radial-spoke portion between the A-tubule-binding base and the neck, GO:0001534 denotes the complete radial spoke, GO:0120343 denotes the radial spoke neck, and GO:0001535 denotes the radial spoke head.
CURATION_TODO (OPEN): Resolve exact source-neutral groundings and copy numbers for Chlamydomonas radial-spoke-stalk RSP proteins. Poghosyan et al. 2020 assigned individual Chlamydomonas RSP densities to the stalk region, but this first child-subcomplex record keeps a reviewed-label-only aggregate instead of guessing exact InterPro, Pfam, NCBIfam, or UniProtKB groundings and cross-species boundaries.

Evidence

GO:0001536 Gene Ontology cellular-component term for the radial spoke stalk.
GO:0032991 Gene Ontology cellular-component term for protein-containing complex.
GO:0001534 Gene Ontology cellular-component term for the containing radial spoke.
GO:0120343 Gene Ontology cellular-component term for the radial spoke neck.
DOI:10.1126/science.1128618 Nicastro et al. 2006, 'The molecular architecture of axonemes revealed by cryoelectron tomography', Science.
DOI:10.1242/jcs.245233 Poghosyan et al. 2020, 'The structure and symmetry of the radial spoke protein complex in Chlamydomonas flagella', Journal of Cell Science.

Curation history

2026-09-30T00:51:27Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-30T00:52:19Z codex · EXPANDED_RECORD — Added protein-complex parentage, radial-spoke parthood, a reviewed-label-only stalk-protein constituent, Chlamydomonas scope and canonical example, an outer-doublet-linkage function, GO/DOI evidence, a nonmechanistic topology graph, and boundary and component-grounding discussions.
2026-09-30T01:02:11Z codex · REFINE_STALK_TOPOLOGY — Narrowed the stalk graph so the GO:0001536 stalk connects to a radial-spoke base node rather than directly to the axonemal doublet microtubule.

Source: data/structures/cytoskeleton/radial_spoke_stalk.yaml