BtubAB bacterial microtubule

cellstructuremech:btubab_bacterial_microtubule · Cytoskeleton · Filament · Proposed

A bacterial cytoskeletal microtubule assembled from BtubA and BtubB tubulin homologs that form tube-like filaments in Prosthecobacter cells and in purified BtubA/B reactions. [DOI:10.1371/journal.pbio.1001213]

Synonyms: bacterial microtubule; bMT

Part of: GO:0005856 — cytoskeleton (no local record)

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

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
BtubA	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	btubA	ESSENTIAL	Bacterial tubulin subunit that co-assembles with BtubB into the BtubAB microtubule protofilaments. `DOI:10.1073/pnas.012516899` Jenkins et al. 2002 identified bacterial tubulin A among the tubulin-like proteins encoded by Prosthecobacter. `DOI:10.1371/journal.pbio.1001213` Pilhofer et al. 2011 imaged BtubA/B tubes in Prosthecobacter and in recombinant or purified BtubA/B assembly reactions. `DOI:10.1073/pnas.1705062114` Deng et al. 2017 resolved purified BtubABC mini-microtubules and modeled BtubA as one alternating tubulin subunit in the polymer.
BtubB	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	btubB	ESSENTIAL	Bacterial tubulin subunit that co-assembles with BtubA into the BtubAB microtubule protofilaments. `DOI:10.1073/pnas.012516899` Jenkins et al. 2002 identified bacterial tubulin B among the tubulin-like proteins encoded by Prosthecobacter. `DOI:10.1371/journal.pbio.1001213` Pilhofer et al. 2011 localized BtubA and BtubB proteins to Prosthecobacter tube-like structures and reconstituted BtubA/B tube assembly. `DOI:10.1073/pnas.1705062114` Deng et al. 2017 resolved purified BtubABC mini-microtubules and modeled BtubB as one alternating tubulin subunit in the polymer.
BtubC	Protein	acts on	Reviewed label only (reviewed name; no accession asserted)	btubC	UNKNOWN	Bacterial kinesin-light-chain-like protein that binds along BtubAB microtubules; purified BtubABC and membrane-linking assays support polymer decoration and in vitro membrane association. `DOI:10.1073/pnas.1705062114` Deng et al. 2017 resolved BtubC decorating the exterior of purified BtubABC mini-microtubules. `DOI:10.1038/srep45668` Akendengue et al. 2017 reported that Bklc/BtubC co-localizes with the bacterial tubulin cytoskeleton and links Btub filaments to membranes in vitro.

Taxonomic distribution

NCBITaxon:48466 Prosthecobacter vanneervenii — COMMON: Prosthecobacter vanneervenii was the native bacterium in which BtubA/B cytoplasmic tubes were directly imaged by electron cryotomography. [DOI:10.1371/journal.pbio.1001213]

Canonical examples

NCBITaxon:48466 Prosthecobacter vanneervenii — Verrucomicrobiota species used for the in vivo cryotomograms that defined BtubA/B bacterial microtubules as cytoplasmic five-protofilament tubes. [DOI:10.1371/journal.pbio.1001213]

Mechanism graphs

BtubA/B subunits form a bacterial microtubule (ASSEMBLY)

BtubA and BtubB co-assemble into tubulin-like microtubules, and BtubC binds the BtubAB polymer exterior as stabilizing associated machinery.

Subject	Predicate	Object	Evidence
BtubA	co-assembles into	BtubAB bacterial microtubule	`DOI:10.1371/journal.pbio.1001213` Pilhofer et al. 2011 assigned BtubA/B proteins to tube-like structures in Prosthecobacter and reconstituted bacterial microtubule-like tubes. `DOI:10.1073/pnas.1705062114` Deng et al. 2017 resolved alternating BtubA and BtubB subunits in a purified mini-microtubule.
BtubB	co-assembles into	BtubAB bacterial microtubule	`DOI:10.1371/journal.pbio.1001213` Pilhofer et al. 2011 assigned BtubA/B proteins to tube-like structures in Prosthecobacter and reconstituted bacterial microtubule-like tubes. `DOI:10.1073/pnas.1705062114` Deng et al. 2017 resolved alternating BtubA and BtubB subunits in a purified mini-microtubule.
BtubC	binds	BtubAB bacterial microtubule	`DOI:10.1073/pnas.1705062114` Deng et al. 2017 resolved BtubC decorating purified BtubABC mini-microtubules.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral grounding for Prosthecobacter BtubA and BtubB bacterial tubulins. This first record curates bacterial tubulins from BtubAB-forming Prosthecobacter without asserting that a broad FtsZ/tubulin-family GTPase domain or eukaryotic tubulin-family accession exactly denotes full-length BtubA/B microtubule subunits.
CURATION_TODO (OPEN): Resolve exact source-neutral grounding for BtubC/Bklc proteins. This first record curates BtubC as membrane-linking associated machinery for BtubAB bacterial microtubules without asserting that a tetratricopeptide-repeat or kinesin-light-chain-like domain accession exactly denotes this Prosthecobacter protein class.
INTERPRETATION (RESOLVED): BtubC is associated Btub cytoskeleton machinery rather than an alternating bacterial tubulin subunit. BtubC decorates the outside of the BtubAB mini-microtubule and links Btub cytoskeletal filaments to membranes; BtubA and BtubB are the tubulin homologs that make the alternating protofilament polymer.
INTERPRETATION (RESOLVED): BtubC essentiality is left unknown instead of dispensable for native Prosthecobacter BtubAB microtubules. Purified BtubA/B can form tubes without BtubC, supporting BtubC as an associated factor rather than an alternating tubulin constituent, but the first record does not cite a native Prosthecobacter loss-of-BtubC assembly assay.
INTERPRETATION (RESOLVED): BtubC in vitro membrane-linking activity is not modeled as a native bacterial-membrane assembly edge. Bklc/BtubC links BtubAB filaments with membranes in vitro, but the assembly graph only keeps directly structure-scoped BtubA/B polymerization and BtubC binding to the BtubAB polymer.

Evidence

DOI:10.1073/pnas.012516899 Jenkins, Samudrala, Anderson, Hedlund and Petroni 2002, 'Genes for the cytoskeletal protein tubulin in the bacterial genus Prosthecobacter', PNAS.
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:10.1038/srep45668 Akendengue et al. 2017, 'Bacterial Kinesin Light Chain (Bklc) Links the Btub Cytoskeleton to Membranes', Scientific Reports.
GO:0005856 — cytoskeleton The containing cytoskeletal framework; this filament system is part of it, not a type of the whole framework.
GO:0099513 — polymeric cytoskeletal fiber Broader polymeric cytoskeletal fiber class; this specific protein polymer retains its local identity.

Curation history

2026-09-11T12:03:51Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-11T12:04:54Z codex · EXPANDED_RECORD — Added cytoskeleton parentage, bacterial microtubule synonymy, BtubA/B and BtubC component curation, Prosthecobacter vanneervenii scope, DOI evidence, a nonmechanistic BtubABC assembly graph, Btub family and BtubC grounding TODOs, and a BtubC boundary discussion.
2026-09-11T12:13:20Z codex · REVIEW_FIX — Addressed PR review issues #476 and #477 by changing BtubC essentiality to UNKNOWN, removing the in vitro membrane-linking edge from the assembly graph, and adding resolved boundary discussions.
2026-10-11T17:56:28Z codex · ADDRESS_SAVED_REVIEW — Addressed #2231: Corrected cytoskeleton parthood and retained the specific filament-system identity.

Source: data/structures/cytoskeleton/btubab_bacterial_microtubule.yaml