radial spoke head
Protein complex forming portion of the radial spoke that is orthogonal to the elongated stalk and which projects towards the central pair of microtubules within the ciliary or flagellum axoneme. [GO:0001535]
Part of: radial spoke (GO:0001534)
Components
| Component | Type | Part of / acts on | Grounding | Genes | Stoichiometry | Essential | Role |
|---|---|---|---|---|---|---|---|
| radial spoke head proteins | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Protein constituents of the globular radial-spoke head that projects toward the axonemal central pair.
|
Taxonomic distribution
NCBITaxon:3055Chlamydomonas reinhardtii — COMMON: Chlamydomonas flagellar axonemes carry radial spokes with globular head subcomplexes resolved by cryo-EM. [DOI:10.1242/jcs.245233]
Canonical examples
NCBITaxon:3055Chlamydomonas reinhardtii — Green-algal model whose radial-spoke heads project toward the central pair in 9+2 flagellar axonemes. [DOI:10.1126/science.1128618]
Functions
- radial spoke head central-pair coupling — The radial spoke head forms the central-pair-facing tip of the radial spoke within the axonemal motility transducer apparatus.
GO:0001535GO:0001535 defines the radial spoke head by its projection toward the axonemal central pair.DOI:10.1242/jcs.245233Poghosyan et al. 2020 describe the Chlamydomonas radial spoke as a complex in the ciliary motility transducer apparatus and assign head-region proteins.
Mechanism graphs
Radial-spoke head topology (FUNCTION)
Radial-spoke-head proteins form the central-pair-facing head of the axonemal radial spoke.
| Subject | Predicate | Object | Evidence |
|---|---|---|---|
| radial spoke head proteins | contributes to | radial spoke head |
|
| radial spoke head | is part of | radial spoke |
|
| radial spoke head | projects toward | axonemal central pair |
|
Discussions
- INTERPRETATION (RESOLVED): Keep the radial spoke head distinct from the whole radial spoke and adjacent neck and stalk subcomplexes. GO:0001535 denotes the terminal protein-complex portion of the radial spoke that projects toward the central pair, GO:0001534 denotes the complete radial spoke, GO:0120343 denotes the radial spoke neck, and GO:0001536 denotes the radial spoke stalk.
- CURATION_TODO (OPEN): Resolve exact source-neutral groundings and copy numbers for Chlamydomonas radial-spoke-head RSP proteins. Poghosyan et al. 2020 assigned individual Chlamydomonas RSP densities to the head 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:0001535Gene Ontology cellular-component term for the radial spoke head.GO:0032991Gene Ontology cellular-component term for protein-containing complex.GO:0001534Gene Ontology cellular-component term for the containing radial spoke.DOI:10.1126/science.1128618Nicastro et al. 2006, 'The molecular architecture of axonemes revealed by cryoelectron tomography', Science.DOI:10.1242/jcs.245233Poghosyan et al. 2020, 'The structure and symmetry of the radial spoke protein complex in Chlamydomonas flagella', Journal of Cell Science.
Curation history
2026-09-29T23:26:09Zcodex · CREATED_RECORD — Scaffolded by scripts/new_record.py2026-09-29T23:27:21Zcodex · EXPANDED_RECORD — Added protein-complex parentage, radial-spoke parthood, a reviewed-label-only head-protein constituent, Chlamydomonas scope and canonical example, a central-pair-facing function, GO/DOI evidence, a nonmechanistic topology graph, and boundary and component-grounding discussions.2026-09-30T00:09:09Zcodex · FIX_PARENT_STRUCTURE — Replaced the erroneous GO:0140513 nuclear protein-containing-complex parent with the generic GO:0032991 protein-containing-complex term.