microtubule

GO:0005874 · Cytoskeleton · Filament · Proposed

Any of the long, generally straight, hollow tubes of internal diameter 12-15 nm and external diameter 24 nm found in a wide variety of eukaryotic cells; each consists (usually) of 13 protofilaments of polymeric tubulin, staggered in such a manner that the tubulin monomers are arranged in a helical pattern on the microtubular surface, and with the alpha/beta axes of the tubulin subunits parallel to the long axis of the tubule; exist in equilibrium with pool of tubulin monomers and can be rapidly assembled or disassembled in response to physiological stimuli; concerned with force generation, e.g. in the spindle. [GO:0005874]

Synonyms: microtubuli; microtubulus; neurotubule

Part of: GO:0015630 — microtubule cytoskeleton (no local record)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Taxonomic distribution

• NCBITaxon:3055 Chlamydomonas reinhardtii — COMMON: Chlamydomonas flagella contain axonemal microtubules that have been characterized by cryoelectron tomography. [DOI:10.1126/science.1128618]
• NCBITaxon:5741 Giardia intestinalis — COMMON: Giardia trophozoites contain ventral-disc microtubule arrays that have been mapped by electron tomography. [DOI:10.1371/journal.pone.0043783]

Canonical examples

• NCBITaxon:3055 Chlamydomonas reinhardtii — Green-algal model whose 9+2 flagellar axoneme has been used for cryoelectron-tomographic analysis of eukaryotic microtubule doublets. [DOI:10.1126/science.1128618]
• NCBITaxon:5741 Giardia intestinalis — Parasitic diplomonad model whose ventral-disc microtubule spiral exemplifies a microbial eukaryote-specific microtubule array. [DOI:10.1371/journal.pone.0043783]

Functions

• microtubule cytoskeletal scaffold — Eukaryotic microtubules act as tubulin-polymer scaffolds for microbial structures including Chlamydomonas axonemes and Giardia ventral-disc arrays.
  • DOI:10.1126/science.1128618 Nicastro et al. 2006 resolved the microtubule scaffold of Chlamydomonas axonemes.
  • DOI:10.1371/journal.pone.0043783 Schwartz et al. 2012 resolved the Giardia ventral-disc microtubule spiral and associated dorsal microribbons.

Mechanism graphs

Alpha- and beta-tubulins polymerize into microtubules (ASSEMBLY)

Eukaryotic alpha- and beta-tubulin subunits polymerize into microtubules, the hollow cytoskeletal fibers that make up the microtubule cytoskeleton.

Discussions

• CURATION_TODO (OPEN): Resolve exact source-neutral grounding for the alpha- and beta-tubulins that build canonical eukaryotic microtubules. This first GO:0005874 record curates broad eukaryotic tubulin constituents without asserting that a general tubulin/FtsZ GTPase-domain accession exactly denotes the microtubule alpha/beta-tubulin constituent set.
• CURATION_TODO (OPEN): Curate axonemal doublets, basal-body triplets, haptonemal singlets and other array-specific microtubule subtypes as exact subtypes or array-specific components before mapping them back to GO:0005874. Microbial eukaryotes build specialized microtubule arrays; this generic record records only the shared GO:0005874 polymer boundary and does not flatten doublet, triplet, singlet or ventral-disc-specific morphologies into one component.
• INTERPRETATION (RESOLVED): Keep bacterial, archaeal and phage tubulin-like filaments separate from the GO:0005874 eukaryotic microtubule record. GO:0005874 denotes eukaryotic microtubules built from alpha/beta tubulin into canonical hollow tubes, while this corpus separately models bacterial BtubAB mini-microtubules, bacterial TubZ partition filaments, phage PhuZ spindles, archaeal CetZ filaments and FtsZ-family division rings as non-eukaryotic tubulin/FtsZ-superfamily or tubulin-like cytoskeletal systems with different subunits, architectures or cargo relationships.

Evidence

• GO:0005874 Gene Ontology cellular-component term for the microtubule.
• GO:0099513 — polymeric cytoskeletal fiber Gene Ontology places microtubules under polymeric cytoskeletal fibers.
• GO:0015630 — microtubule cytoskeleton Gene Ontology records microtubules as part of the broader microtubule cytoskeleton.
• DOI:10.1126/science.1128618 Nicastro et al. 2006, 'The molecular architecture of axonemes revealed by cryoelectron tomography', Science.
• 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.
• DOI:10.1186/s13630-016-0039-z Dutcher and O'Toole 2016 reviewed Chlamydomonas reinhardtii basal-body triplet microtubules.
• DOI:10.1242/bio.036590 Nomura et al. 2019 analyzed haptophyte haptonemal microtubules during calcium-dependent coiling.
• DOI:10.1371/journal.pbio.1001213 Pilhofer, Ladinsky, McDowall, Petroni and Jensen 2011, 'Microtubules in bacteria: Ancient tubulins build a five-protofilament homolog of the eukaryotic cytoskeleton', PLoS Biology.
• DOI:10.1073/pnas.1705062114 Deng, Fink, Bharat, He, Kureisaite-Ciziene and Lowe 2017, 'Four-stranded mini microtubules formed by Prosthecobacter BtubAB show dynamic instability', PNAS.
• DOI:10.1101/gad.1546107 Larsen, Cusumano, Fujioka, Lim-Fong, Patterson and Pogliano 2007 characterized bacterial TubZ as a treadmilling prokaryotic tubulin-like plasmid-stability protein.
• DOI:10.7554/eLife.03197 Erb, Kraemer, Coker, Chaikeeratisak, Nonejuie, Agard and Pogliano 2014 characterized PhuZ as a bacteriophage tubulin that forms dynamic filaments.
• DOI:10.1038/nature13983 Duggin et al. 2015 characterized archaeal CetZ tubulin-like proteins as Haloferax cell-shape cytoskeletal factors.
• DOI:10.1146/annurev-biophys-121219-081703 McQuillen and Xiao 2020 reviewed FtsZ rings as tubulin-homolog organizers of bacterial cytokinesis.

Curation history

• 2026-09-16T00:55:25Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
• 2026-09-16T00:56:33Z codex · EXPANDED_RECORD — Added GO microtubule synonyms, polymeric-fiber parentage and microtubule-cytoskeleton parthood, a label-only alpha/beta tubulin component, Chlamydomonas and Giardia scope, DOI/GO evidence, a nonmechanistic tubulin-polymer graph, and curation discussions for tubulin grounding, microtubule subtypes and BtubAB boundaries.
• 2026-09-16T01:06:47Z codex · POLISH_DISCUSSION — Clarified the array-specific microtubule subtype TODO so specialized doublet, triplet, singlet and ventral-disc microtubules are deferred to exact subtype or array-specific component curation rather than implied as generic microtubule components.
• 2026-09-16T01:14:13Z codex · REVIEW_FIXES — Addressed PR #1044 review issues #1045 and #1046 by adding direct basal-body and haptonema evidence to the microtubule subtype TODO and broadening the BtubAB-only boundary to representative bacterial, archaeal and phage tubulin-like filaments.

Source: data/structures/cytoskeleton/microtubule.yaml