TubZ filament

cellstructuremech:tubz_filament · Cytoskeleton · Filament · Proposed

A plasmid-encoded bacterial tubulin-like cytoskeletal filament assembled from TubZ GTPase subunits that supports pBtoxis plasmid partitioning in Bacillus thuringiensis. [DOI:10.1101/gad.1546107]

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	Stoichiometry	Essential	Role
TubZ	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	tubZ		ESSENTIAL	Plasmid-encoded tubulin/FtsZ-family GTPase that polymerizes into dynamic filaments for pBtoxis plasmid partitioning. `DOI:10.1101/gad.1546107` Larsen et al. 2007 characterized Bacillus thuringiensis pBtoxis TubZ as a prokaryotic tubulin-like protein that treadmills and is required for plasmid stability. `DOI:10.1073/pnas.1010176107` Aylett et al. 2010 determined the filament structure of the bacterial tubulin homologue TubZ.

Taxonomic distribution

NCBITaxon:1428 Bacillus thuringiensis — VARIABLE: The TubZ filament is a plasmid-encoded partition filament experimentally characterized from the Bacillus thuringiensis virulence plasmid pBtoxis; it is not asserted to occur in all Bacillus thuringiensis strains. [DOI:10.1101/gad.1546107]

Canonical examples

NCBITaxon:1428 Bacillus thuringiensis — Species hosting the pBtoxis virulence plasmid whose TubZ filaments defined this type III plasmid-partition system. [DOI:10.1101/gad.1546107]

Functions

pBtoxis plasmid partitioning — TubZ filaments interact with TubR-tubC partition complexes to support pBtoxis DNA partitioning and stable plasmid inheritance in Bacillus thuringiensis.
- DOI:10.1101/gad.1546107 Larsen et al. 2007 connected TubZ treadmilling to stable inheritance of the Bacillus thuringiensis pBtoxis plasmid.
- DOI:10.1073/pnas.1003817107 Ni et al. 2010 analyzed TubR DNA binding and TubZ recruitment in the pBtoxis partition system.

Mechanism graphs

TubZ filaments support pBtoxis plasmid partitioning (FUNCTION)

TubZ polymerizes into tubulin-like filaments and TubR bound to pBtoxis tubC centromere DNA engages TubZ filaments to support plasmid partitioning.

Subject	Predicate	Object	Evidence
TubZ	polymerizes into	TubZ filament	`DOI:10.1101/gad.1546107` Larsen et al. 2007 characterized TubZ polymers from the pBtoxis plasmid. `DOI:10.1073/pnas.1010176107` Aylett et al. 2010 solved the TubZ filament structure.
TubR-tubC complex	engages	TubZ filament	`DOI:10.1073/pnas.1003817107` Ni et al. 2010 reported TubR DNA binding and recruitment of TubZ for DNA partition.
TubZ filament	supports	pBtoxis plasmid partitioning	`DOI:10.1101/gad.1546107` Larsen et al. 2007 connected TubZ treadmilling to pBtoxis plasmid stability. `DOI:10.1073/pnas.1210899109` Aylett and Lowe 2012 analyzed the pBtoxis TubR-tubC centromeric partition complex.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral grounding for plasmid-encoded filament-forming TubZ GTPases. This first record curates TubZ from the Bacillus thuringiensis pBtoxis partition system without asserting that a broad tubulin/FtsZ GTPase domain accession exactly denotes TubZ filament-forming proteins.
INTERPRETATION (RESOLVED): TubR and tubC centromere DNA are graph-scoped partition adapters rather than TubZ filament constituents. TubR bound to the pBtoxis tubC centromere site engages TubZ filaments in the TubZRC partition system, but this centromeric complex is cargo-coupling machinery rather than a TubZ polymer subunit.

Evidence

DOI:10.1101/gad.1546107 Larsen, Cusumano, Fujioka, Lim-Fong, Patterson and Pogliano 2007, 'Treadmilling of a prokaryotic tubulin-like protein, TubZ, required for plasmid stability in Bacillus thuringiensis', Genes & Development.
DOI:10.1073/pnas.1010176107 Aylett, Wang, Michie, Amos and Lowe 2010, 'Filament structure of bacterial tubulin homologue TubZ', PNAS.
DOI:10.1073/pnas.1003817107 Ni, Xu, Kumaraswami and Schumacher 2010, 'Plasmid protein TubR uses a distinct mode of HTH-DNA binding and recruits the prokaryotic tubulin homolog TubZ to effect DNA partition', PNAS.
DOI:10.1073/pnas.1210899109 Aylett and Lowe 2012, 'Superstructure of the centromeric complex of TubZRC plasmid partitioning systems', PNAS.
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

2026-09-11T11:25:27Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-11T11:26:08Z codex · EXPANDED_RECORD — Added cytoskeleton parentage, TubZ component curation, Bacillus thuringiensis pBtoxis scope, pBtoxis partitioning function, DOI evidence, a nonmechanistic TubZRC graph, and TubZ grounding and TubR/tubC boundary discussions.
2026-09-11T11:26:26Z codex · NARROW_SYNONYMY — Removed the pBtoxis TubZ filament related synonym because it was a curator paraphrase rather than an attested alternate label.
2026-09-11T11:34:57Z codex · REVIEW_FIX — Addressed PR review issues #470 and #471 by naming pBtoxis tubC in the TubR-tubC graph node and retargeting the adapter edge from TubZ monomers to TubZ filaments.
2026-10-11T17:56:35Z codex · ADDRESS_SAVED_REVIEW — Addressed #2233: Corrected cytoskeleton parthood and retained the specific filament-system identity.

Source: data/structures/cytoskeleton/tubz_filament.yaml