bactofilin filament

cellstructuremech:bactofilin_filament · Cytoskeleton · Filament · Proposed

A cytoskeletal filament assembled from beta-helical bactofilin proteins. In bacteria, these filaments provide scaffolds for species-specific cellular organization, including polar stalk biogenesis in Caulobacter vibrioides. [DOI:10.1038/s41564-019-0544-0]

Synonyms: bactofilin cytoskeleton; Caulobacter BacA/BacB polar bactofilin scaffold

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
bactofilin proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	bacA, bacB		ESSENTIAL	Beta-helical cytoskeletal proteins that self-assemble into bactofilin filaments; the bacterial family is not exclusive to Bacteria. `DOI:10.1038/emboj.2009.358` Kuhn et al. 2010 identified BacA and BacB as Caulobacter bactofilins that assemble into a membrane-proximal polar cytoskeletal structure. `DOI:10.1038/s41564-019-0544-0` Deng et al. 2019 structurally analyzed bactofilin filaments and demonstrated in vitro polymerization of recombinant Phytophthora infestans PiBac as well as bacterial proteins.

Taxonomic distribution

NCBITaxon:2 Bacteria — VARIABLE: Bactofilins are widespread bacterial cytoskeletal proteins, but the family is not asserted to be universal across Bacteria. [DOI:10.1038/emboj.2009.358]
NCBITaxon:155892 Caulobacter vibrioides — COMMON: Caulobacter vibrioides BacA and BacB cooperate to form a polar bactofilin structure that recruits the PbpC cell wall synthase. [DOI:10.1038/emboj.2009.358]

Canonical examples

NCBITaxon:565050 Caulobacter vibrioides NA1000 — Model Caulobacter strain used to identify BacA/BacB bactofilin polymers and PbpC recruitment to the stalked cell pole. [DOI:10.1038/emboj.2009.358]

Functions

Caulobacter stalk biogenesis scaffold — The BacA/BacB bactofilin structure in Caulobacter vibrioides recruits the PbpC peptidoglycan synthase to the stalked pole for stalk biogenesis.
- DOI:10.1038/emboj.2009.358 Kuhn et al. 2010 showed that Caulobacter BacA and BacB recruit PbpC to the stalked pole and support stalk morphogenesis.

Mechanism graphs

BacA/BacB bactofilins recruit PbpC to the Caulobacter stalked pole (FUNCTION)

Caulobacter BacA and BacB assemble into a polar bactofilin scaffold that localizes the PbpC cell-wall synthase and supports stalk biogenesis.

Subject	Predicate	Object	Evidence
BacA and BacB bactofilins	polymerize into	bactofilin filament	`DOI:10.1038/emboj.2009.358` Kuhn et al. 2010 localized Caulobacter BacA and BacB to the same polar cytoskeletal structure.
bactofilin filament	localizes to	Caulobacter stalked pole	`DOI:10.1038/emboj.2009.358` Kuhn et al. 2010 observed a polar BacA/BacB structure near the stalked pole.
bactofilin filament	recruits	PbpC	`DOI:10.1038/emboj.2009.358` Kuhn et al. 2010 showed that BacA/BacB are needed for PbpC polar localization.
PbpC	supports	Caulobacter stalk biogenesis	`DOI:10.1038/emboj.2009.358` Kuhn et al. 2010 connected PbpC localization by bactofilins to Caulobacter stalk morphogenesis.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral grounding for full-length filament-forming bactofilin proteins. This first record curates experimentally demonstrated bactofilin filament formation without asserting that a single unverified domain or family accession captures the full bactofilin constituent class.
INTERPRETATION (RESOLVED): Separate bactofilin family scope from native structural occurrence. Deng et al. 2019 demonstrate in vitro filament formation by recombinant PiBac from the oomycete Phytophthora infestans. Their archaeal bactofilin-domain sequence hits are a different evidence level and do not establish archaeal filament formation.

Evidence

DOI:10.1038/emboj.2009.358 Kuhn, Briegel, Morschel, Kahnt, Leser et al. 2010, 'Bactofilins, a ubiquitous class of cytoskeletal proteins mediating polar localization of a cell wall synthase in Caulobacter crescentus', EMBO Journal.
DOI:10.1073/pnas.1418450112 Vasa et al. 2015, 'beta-Helical architecture of cytoskeletal bactofilin filaments revealed by solid-state NMR', PNAS.
DOI:10.1038/s41564-019-0544-0 Deng et al. 2019, 'The structure of bactofilin filaments reveals their mode of membrane binding and lack of polarity', Nature Microbiology.
GO:0099513 — polymeric cytoskeletal fiber Broader polymeric cytoskeletal fiber class; this protein filament retains its specific local identity.
GO:0005856 — cytoskeleton The cytoskeletal framework contains this filament; the filament is part of it, not a type of the entire framework.

Curation history

2026-09-11T10:12:30Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-11T10:13:21Z codex · EXPANDED_RECORD — Added cytoskeleton parentage, bactofilin synonymy and component curation, bacterial and Caulobacter vibrioides scope, a Caulobacter stalk-scaffold function, DOI evidence, a nonmechanistic BacA/BacB-to-PbpC graph, and a bactofilin grounding TODO.
2026-09-11T10:21:49Z codex · REVIEW_FIX — Addressed PR review issues #459 and #460 by softening the Caulobacter BacA/BacB synonym from a narrow filament synonym to a related polar-scaffold synonym and removing unsupported BacM gene-symbol scope.
2026-10-11T18:52:23Z codex · ADDRESS_SAVED_REVIEW — Addressed #2242, #2243: Corrected cytoskeletal fiber is-a and containing-framework parthood. Removed bacteria-specific family wording and grounded the broader architecture in Deng 2019. An appended discussion distinguishes demonstrated recombinant PiBac polymerization from unproven native oomycete function and archaeal sequence hits. Existing bacterial occurrences and Caulobacter graph are unchanged.

Source: data/structures/cytoskeleton/bactofilin_filament.yaml