ParM filament

cellstructuremech:parm_filament · Cytoskeleton · Filament · Proposed

A plasmid-encoded bacterial actin-like cytoskeletal filament assembled from ParM that is captured and stabilized by ParR-parC plasmid-centromere complexes to support active segregation of low-copy-number plasmids such as Escherichia coli R1. [DOI:10.1093/emboj/cdf320]

Synonyms: R1 ParM filament; bacterial actin-like ParM filament

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
ParM	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	parM		ESSENTIAL	Plasmid-encoded actin-like ATPase subunit that polymerizes into the dynamically unstable filaments of the ParMRC partition system. `DOI:10.1093/emboj/cdf320` Moller-Jensen et al. 2002 identified R1 plasmid ParM as the actin-like protein forming filaments for active plasmid segregation. `DOI:10.1126/science.1101313` Garner et al. 2004 showed that purified ParM filaments undergo dynamic instability in vitro.

Taxonomic distribution

NCBITaxon:2 Bacteria — VARIABLE: Actin-like ParM partition filaments are plasmid-encoded bacterial systems and are not asserted to be universal across Bacteria. [DOI:10.1038/nrmicro2425]

Canonical examples

NCBITaxon:562 Escherichia coli — Host species for the low-copy-number R1 plasmid whose ParMRC partition system defined ParM filament-driven plasmid segregation. [DOI:10.1093/emboj/cdf320]

Functions

R1 plasmid segregation — ParR-parC complexes on paired R1 plasmids capture ParM filaments, and stabilized filament elongation moves sister plasmids apart before host-cell division.
- DOI:10.1093/emboj/cdf320 Moller-Jensen et al. 2002 connected ParM filament assembly to active segregation of the R1 plasmid.
- DOI:10.1126/science.1229091 Gayathri et al. 2012 reconstituted the antiparallel ParM filament spindle that drives plasmid segregation.

Mechanism graphs

ParM filaments separate R1 plasmids (FUNCTION)

ParM polymerizes into actin-like filaments that are captured by ParR-parC complexes on R1 plasmids; stabilized filament elongation supports plasmid segregation.

Subject	Predicate	Object	Evidence
ParM	polymerizes into	ParM filament	`DOI:10.1093/emboj/cdf320` Moller-Jensen et al. 2002 observed R1 ParM filaments in bacterial cells. `DOI:10.1126/science.1101313` Garner et al. 2004 followed purified ParM polymerization dynamics.
ParM filament	is captured by	ParR-parC plasmid-centromere complex	`DOI:10.1126/science.1229091` Gayathri et al. 2012 reconstituted ParR/parC-dependent capture of ParM filaments.
ParM filament	supports	R1 plasmid segregation	`DOI:10.1126/science.1229091` Gayathri et al. 2012 reconstituted plasmid separation by antiparallel ParM filaments.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral grounding for plasmid-encoded filament-forming ParM proteins. This first record curates ParM from the R1 plasmid partition system without asserting that a broad actin-like ATPase family accession exactly denotes ParM filament-forming proteins.
INTERPRETATION (RESOLVED): ParR and parC are graph-scoped capture machinery rather than ParM filament constituents. ParR bound to the parC plasmid centromere captures and stabilizes ParM filament ends in the partition spindle, so the graph keeps the ParR-parC complex as capture machinery while the component list keeps only the ParM polymer subunit as a constituent.

Evidence

DOI:10.1093/emboj/cdf320 Moller-Jensen, Jensen, Lowe and Gerdes 2002, 'Prokaryotic DNA segregation by an actin-like filament', EMBO Journal.
DOI:10.1126/science.1101313 Garner, Campbell and Mullins 2004, 'Dynamic instability in a DNA-segregating prokaryotic actin homolog', Science.
DOI:10.1126/science.1229091 Gayathri, Fujii, Moller-Jensen, van den Ent, Namba and Lowe 2012, 'A bipolar spindle of antiparallel ParM filaments drives bacterial plasmid segregation', Science.
DOI:10.1038/nature14356 Bharat, Murshudov, Sachse and Lowe 2015, 'Structures of actin-like ParM filaments show architecture of plasmid-segregating spindles', Nature.
DOI:10.1038/nrmicro2425 Salje, Gayathri and Lowe 2010, 'The ParMRC system: molecular mechanisms of plasmid segregation by actin-like filaments', Nature Reviews 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

2026-09-11T10:32:38Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-11T10:33:30Z codex · EXPANDED_RECORD — Added cytoskeleton parentage, ParM filament synonymy and component curation, plasmid-host bacterial scope, R1 plasmid segregation function, DOI evidence, a nonmechanistic ParM-to-R1 segregation graph, and ParM grounding and ParR/parC boundary discussions.
2026-09-11T10:40:25Z codex · FIX_DISCUSSION_ANCHOR — Retargeted the ParR/parC component-boundary discussion from the whole components section to the concrete ParM component anchor.
2026-09-11T10:44:43Z codex · REVIEW_FIX — Addressed PR review issues #462 and #463 by adding a graph-local ParR-parC centromere-complex node, remodeling the final graph edge as ParM-filament support for R1 plasmid segregation, and retargeting the ParR/parC component-boundary discussion to the causal graph.
2026-10-11T18:52:20Z codex · ADDRESS_SAVED_REVIEW — Addressed #2241: Corrected cytoskeletal fiber is-a and containing-framework parthood.

Source: data/structures/cytoskeleton/parm_filament.yaml