ventral disc dorsal microribbon

GO:0097594 · Cytoskeleton · Filament · Proposed

Trilaminar structure extending perpendicularly into the cytoplasm along the length of ventral disc microtubules in Giardia species (trophozoite stage). Constituents of dorsal microribbons (also called dorsal ribbons or microribbons) include alpha-coiled-helix proteins approximately 29 to 38 kDa in size. These proteins line the edges of the microribbons but are not found in microtubules. Tubulins are not found in microribbons. [GO:0097594]

Synonyms: dorsal microribbon; dorsal ribbon; microribbon; ventral disk dorsal microribbon

Part of: ventral disc (GO:0097597)

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
microribbon striated-fiber-assemblin homologs	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Alpha-helical microribbon proteins, including beta-giardin, delta-giardin and SALP-1-like constituents, that build the proteinaceous Giardia ventral-disc dorsal microribbon. `GO:0097594` Gene Ontology describes dorsal microribbons as trilaminar structures containing alpha-coiled-helix proteins of approximately 29 to 38 kDa. `DOI:10.1371/journal.pone.0043783` Schwartz et al. 2012 describe microribbons as ventral-disc structures containing striated fiber-assemblin homologs such as beta-giardin, delta-giardin and SALP-1.

Taxonomic distribution

NCBITaxon:5741 Giardia intestinalis — COMMON: Giardia intestinalis is the diplomonad species in which ventral-disc dorsal microribbons were mapped alongside ventral-disc microtubules and crossbridges. [DOI:10.1371/journal.pone.0043783]

Canonical examples

NCBITaxon:5741 Giardia intestinalis — Parasitic diplomonad model used for electron-tomographic mapping of the ventral-disc microtubule and dorsal microribbon scaffold. [DOI:10.1371/journal.pone.0043783]

Functions

ventral disc microribbon scaffold — The dorsal microribbons extend from Giardia ventral-disc microtubules into the cytoplasm and are connected by crossbridges, contributing a proteinaceous scaffold to the ventral disc.
- GO:0097594 Gene Ontology defines the dorsal microribbon as a trilaminar structure that extends from ventral-disc microtubules into the cytoplasm.
- DOI:10.1371/journal.pone.0043783 Schwartz et al. 2012 mapped the trilaminar microribbon and its crossbridges by cryo-electron tomography and sub-tomogram averaging.

Mechanism graphs

Striated-fiber-assemblin homologs build Giardia dorsal microribbons (ASSEMBLY)

In Giardia, striated-fiber-assemblin homologs constitute ventral-disc dorsal microribbons that extend from the microtubule spiral and are laterally linked by crossbridges.

Subject	Predicate	Object	Evidence
microribbon striated-fiber-assemblin homologs	constitute	ventral disc dorsal microribbon	`GO:0097594` Gene Ontology lists alpha-coiled-helix proteins as constituents of dorsal microribbons. `DOI:10.1371/journal.pone.0043783` Schwartz et al. 2012 discuss beta-giardin, delta-giardin and SALP-1 striated-fiber-assemblin homologs in dorsal microribbons.
ventral disc dorsal microribbon	extends from	ventral disc microtubule array	`GO:0097594` Gene Ontology defines dorsal microribbons as extending along ventral-disc microtubules.
ventral disc crossbridge	links	ventral disc dorsal microribbon	`GO:0097595` Gene Ontology defines ventral-disc crossbridges as links between adjacent microribbons.
ventral disc dorsal microribbon	is part of	ventral disc	`GO:0097594` Gene Ontology models GO:0097594 as part of GO:0097597, the ventral disc.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings and finer subcomponent boundaries for Giardia dorsal-microribbon beta-giardin, delta-giardin, SALP-1 and related alpha-coiled-helix proteins. This first dorsal-microribbon record curates a broad striated-fiber-assemblin homolog cohort because GO and Schwartz et al. define the microribbon as a proteinaceous trilaminar structure, but this pass did not verify exact protein-family CURIEs or stable boundaries for the individual giardin and SALP constituents.

Evidence

GO:0097594 Gene Ontology cellular-component term for the Giardia ventral-disc dorsal microribbon.
DOI:10.1371/journal.pone.0043783 Schwartz, Heumann, Dawson and Hoenger 2012, 'A Detailed, Hierarchical Study of Giardia lamblia's Ventral Disc Reveals Novel Microtubule-Associated Protein Complexes', PLOS ONE.

Curation history

2026-09-15T15:05:56Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-15T15:06:43Z codex · EXPANDED_RECORD — Added GO dorsal-microribbon synonyms, ventral-disc partonomy, a label-only striated-fiber-assemblin component, Giardia intestinalis scope, DOI evidence, a nonmechanistic microribbon architecture graph, and a microribbon-protein grounding TODO.
2026-09-15T15:21:27Z codex · REVIEW_FIX — Addressed PR #990 review issue #991 by reclassifying the dorsal microribbon constituent-and-partonomy graph as ASSEMBLY.

Source: data/structures/cytoskeleton/ventral_disc_dorsal_microribbon.yaml