elongasome

cellstructuremech:elongasome · Division machinery · Multiprotein complex · Proposed

The membrane-associated Rod complex that synthesizes lateral peptidoglycan during rod-shaped growth in model bacteria such as Escherichia coli and Bacillus subtilis. Its SEDS-family RodA polymerase works with an elongation-specific class B penicillin-binding transpeptidase, PBP2 in E. coli. Associated MreB filaments orient synthesis, while wall synthesis and filament motion are coupled; this is not a universal mechanism of rod shape in all bacteria. [DOI:10.1038/nmicrobiol.2016.172]

Synonyms: Rod complex; RodA-PBP2 complex

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

Components

Component	Type	Part of / acts on	Genes	Essential	Role
SEDS glycosyltransferase RodA	Protein	part of	rodA	ESSENTIAL	Polymerises the glycan strand; the SEDS-family partner of the class B PBP. `DOI:10.1038/nature19331` — Here, we have presented evidence that the SEDS family protein RodA is the principal PGT in the Rod complex and is likely to be responsible for its dynamic movement. Verbatim from PMC5161649. Meeske et al.2016 establish RodA polymerase activity in B. subtilis. Typas et al.2011 do mention RodA in Table1 and Figure1, with a then-proposed flippase function; mentioning the protein is different from establishing its later polymerase activity. Earlier history asserting the name was absent is retained as historical provenance, not current evidence. `DOI:10.1038/nature19331` — RodA is a member of the SEDS family of proteins that play essential but ill-defined roles in cell wall biogenesis during growth, division and sporulation. Verbatim; supports the SEDS family assignment in the component label.
class B penicillin-binding protein PBP2	Protein	part of	mrdA, pbpA	ESSENTIAL	Crosslinks the new glycan strands into the existing sacculus; the target of mecillinam. `DOI:10.1038/nrmicro2677` Typas et al. 2011 describe PBP2 as the elongation-specific crosslinking enzyme.
MreC and MreD	Protein	part of	mreC, mreD	ESSENTIAL	Membrane and periplasmic subunits that hold the synthases in an active arrangement. Moved here from the MreB filament record, where they were mis-scoped: they build this machine, not the filament (#102). `DOI:10.1038/nrmicro2677` Typas et al. 2011 place MreC and MreD within the elongation complex.
RodZ	Protein	acts on	rodZ	CONDITIONAL	Couples MreB to wall-synthesis proteins in E. coli. RodZ loss impairs MreB rotation in ordinary backgrounds, but suppressors can restore rod shape without restoring rotation. `DOI:10.1016/j.cell.2018.02.050` Shi et al. 2018 describe RodZ coupling MreB to the synthetic complex. `DOI:10.1073/pnas.1509610112` Complete primary abstract: RodZ links MreB rotation to wall synthesis; suppressors restore shape without rotation in standard laboratory conditions. Full Methods were not available in this review.

Organism-specific protein examples

Named proteins in which each component's role was established, with the organism the evidence comes from. The component above is the taxon-agnostic family; these are the specific entries behind it.

SEDS glycosyltransferase RodA

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P0ABG7`	Peptidoglycan glycosyltransferase MrdB	mrdB	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene rodA, which UniProt lists under the primary name mrdB, in Escherichia coli K-12, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:6348029` Stoker NG et al. 1983, ‘Identification of the rodA gene product of Escherichia coli.’, J Bacteriol. ECO:0000269 experimental evidence cited by UniProt for the 'Cell inner membrane' localisation of P0ABG7.

class B penicillin-binding protein PBP2

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P0AD65`	Peptidoglycan D,D-transpeptidase MrdA	mrdA	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (2 references) The single reviewed UniProtKB entry for gene mrdA in Escherichia coli K-12, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:1103132` Spratt BG 1975, ‘Distinct penicillin binding proteins involved in the division, elongation, and shape of Escherichia coli K12.’, Proc Natl Acad Sci U S A. ECO:0000269 experimental evidence cited by UniProt for the 'Cell inner membrane' localisation of P0AD65. `PMID:3009484` Ishino F et al. 1986, ‘Peptidoglycan synthetic activities in membranes of Escherichia coli caused by overproduction of penicillin-binding protein 2 and rodA protein.’, J Biol Chem. ECO:0000269 experimental evidence cited by UniProt for the 'Cell inner membrane' localisation of P0AD65.

MreC and MreD

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P16926`	Cell shape-determining protein MreC	mreC	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene mreC in Escherichia coli K-12, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:15612918` Kruse T et al. 2005, ‘The morphogenetic MreBCD proteins of Escherichia coli form an essential membrane-bound complex.’, Mol Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Cell inner membrane' localisation of P16926.
`UniProtKB:P0ABH4`	Rod shape-determining protein MreD	mreD	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene mreD in Escherichia coli K-12, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `https://www.uniprot.org/uniprotkb/P0ABH4` UniProtKB reviewed (Swiss-Prot) entry P0ABH4, the single reviewed entry for gene mreD in Escherichia coli K-12. Establishes the accession and gene identity only; the component's membership in this structure rests on the record's own sources.

RodZ

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P27434`	Cytoskeleton protein RodZ	rodZ	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene rodZ in Escherichia coli K-12, a taxon this record names; other reviewed entries for this symbol exist on sub-strain nodes and this is the one at the taxon the record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:19008860` Shiomi D et al. 2008, ‘Determination of bacterial rod shape by a novel cytoskeletal membrane protein.’, EMBO J. ECO:0000269 experimental evidence cited by UniProt for the 'Cell inner membrane' localisation of P27434.

Taxonomic distribution

NCBITaxon:2 Bacteria — VARIABLE: Characterized in E. coli and B. subtilis and distributed among many MreB-dependent rod-shaped bacteria; not inferred from rod morphology alone. Some rod-shaped lineages use MreB-independent growth systems. [DOI:10.1016/j.cell.2018.02.050]

Canonical examples

NCBITaxon:83333 Escherichia coli K-12 — Reference system for elongation-specific synthesis and its mecillinam sensitivity. [DOI:10.1038/nrmicro2677]
NCBITaxon:1423 Bacillus subtilis — Reference Gram-positive elongation machinery. [DOI:10.1038/nrmicro2677]

Functions

regulation of cell shape GO:0008360 — Inserts peptidoglycan into the cylindrical sidewall, maintaining width and extending length.
- DOI:10.1038/nrmicro2677 Typas et al. 2011 tie elongation-complex activity to cell shape.
- DOI:10.1016/j.cell.2018.02.050 Shi et al. 2018 link the complex's circumferential motion to rod maintenance.

Associated traits

MODULATES METPO:1000681 rod shaped
- DOI:10.1038/nmicrobiol.2016.172 The Rod system supports rod-shaped growth in E. coli; this is not universal necessity for every rod-shaped bacterium.
- DOI:10.1016/j.cell.2018.02.050 The review describes MreB-independent rod-shaped lineages and shape-restoring suppressors. MODULATES denotes the bounded shape-maintenance role, not sufficiency or universal necessity.

Related pathways

Peptidoglycan cytoplasmic synthesis and recycling pathways (WikiPathways:WP5060) — PARTICIPATES_IN; target taxon NCBITaxon:562.
This refers to sidewall peptidoglycan synthesis in the E. coli exemplar. It does not identify the elongasome with the whole WP5060 pathway or equate the reviewed K-12 PBP2 accession with the separate species-level entry in WP5060.
Basis: The curated sidewall-synthesis function overlaps the peptidoglycan output of WP5060; this is not an exact shared-accession join.. PathwayMech revision: d8ec2b69f7a4c615aecddff80498fef1e1fab0ce.
- DOI:10.1038/nrmicro2677 Typas et al. 2011 review peptidoglycan synthesis complexes and cytoskeletal control of sacculus growth; the existing sidewall-synthesis function provides the structure-specific context. Abstract read through Europe PMC on 2026-10-05.

Mechanism graphs

Rod-system synthesis, MreB rotation and model-specific shape maintenance (FUNCTION)

E. coli RodA/PBP2 synthesize lateral wall, and inhibition experiments couple synthesis to MreB rotation. MreB rotation and synthase movement are separate readouts, not interchangeable with rod shape. RodZ promotes normal MreB rotation, but suppressor backgrounds can retain rod shape without rotation. B. subtilis uses related machinery, including its own elongation-specific transpeptidases; this graph is not a universal inventory or necessity claim.

Subject	Predicate	Object	Evidence
SEDS glycosyltransferase RodA	polymerizes glycans during	peptidoglycan biosynthetic process	`DOI:10.1038/nature19331` B. subtilis biochemical and genetic experiments establish RodA polymerase activity; Cho2016 supplies complementary E. coli evidence.
class B penicillin-binding protein PBP2	crosslinks peptides during	peptidoglycan biosynthetic process	`DOI:10.1038/nmicrobiol.2016.172` Mecillinam perturbation separates glycan polymerization from crosslinking in the E. coli Rod system.
peptidoglycan biosynthetic process	drives coupled	circumferential MreB filament rotation	`DOI:10.1038/nmicrobiol.2016.172` RodA(D262N) inhibits Rod-system polymerization and MreB rotation; aPBP inhibition does not eliminate that rotation before lysis.
RodZ	couples	MreB filament	`DOI:10.1016/j.cell.2018.02.050` Review discusses cytoplasmic MreB binding and periplasmic interactions with synthetic proteins.
RodZ	promotes	circumferential MreB filament rotation	`DOI:10.1073/pnas.1509610112` Complete primary abstract distinguishes normal rotation from suppressor-restored rod shape; not evidence that all synthase movement is absent.
peptidoglycan biosynthetic process	is coupled to	directional RodA-PBP2 movement in E. coli	`DOI:10.1038/nmicrobiol.2016.172` Imaging resolves both nondirectional diffusion and MreB-like circumferential motion for RodA/PBP2; directional fractions respond to Rod-system perturbation.
peptidoglycan biosynthetic process	produces	cylindrical sidewall extension	`DOI:10.1038/nmicrobiol.2016.172` Primary radiolabeling and synthesis perturbations support the wall-producing activity of the Rod system.
MreB filament	supports	rod-shaped cell	`DOI:10.1016/j.cell.2018.02.050` Review describes morphology perturbations, geometric organization and lineage-specific exceptions.
cylindrical sidewall extension	maintains	rod-shaped cell	`DOI:10.1038/nrmicro2677` Review connects spatial control of peptidoglycan growth to bacterial morphology; no universal constant-width law is inferred.

Discussions

KNOWLEDGE_GAP (OPEN): This machine is guided by the MreB filament, and the schema has no relation that says so. The partner statement to the discussion on the MreB filament record (#119). RodZ couples the two, which is recorded in that component's role, but the structure-to-structure relationship has no field.
CURATION_TODO (RESOLVED): Which source establishes the RodA polymerase assignment used in the definition? The definition and synonyms now cite inspected 2016 primary evidence. Typas et al. 2011 mention RodA, but predate the polymerase discovery; absence of that later finding is not absence of the protein name. The RodA component now carries Meeske 2016 with verbatim support (#161), so the claim itself is sourced. What remains is that the record-level definition still attributes it to a review that predates the finding. Rewording a definition changes what the record asserts it is, which is a curator's call, not an automatic edit.

Evidence

DOI:10.1038/nrmicro2677 Typas A, Banzhaf M, Gross CA, Vollmer W 2011, 'From the regulation of peptidoglycan synthesis to bacterial growth and morphology', Nature Reviews Microbiology.
DOI:10.1016/j.cell.2018.02.050 Shi H, Bratton BP, Gitai Z, Huang KC 2018, 'How to Build a Bacterial Cell: MreB as the Foreman of E. coli Construction', Cell.
DOI:10.1038/nmicrobiol.2016.172 Primary E. coli radiolabeling, perturbation and imaging experiments distinguish RodA/PBP2 synthesis from semi-autonomous aPBP activity and the wall product.
DOI:10.1038/nature19331 Primary B. subtilis work establishes RodA as the Rod-complex glycan polymerase.
DOI:10.1038/s41467-021-23099-8 Scope comparison only: archaeal pseudomurein is distinct from bacterial peptidoglycan. This paper does not establish a domain-wide negative assay for the elongasome; the unsupported Archaea ABSENT row is removed without asserting presence.

Curation history

2026-09-02T04:49:54Z claude · CREATED_RECORD — Drafted from the cited reviews; every GO term, taxon id and DOI resolved live before writing. Not yet human-reviewed.
2026-09-02T04:57:03Z claude · ADD_TRAIT_LINK — Self-review of PR #118: linked METPO:1000681 rod shaped, which the machine is required for, and recorded the missing guided-by relation (#119).
2026-09-02T23:48:01Z claude · ADD_CAUSAL_GRAPH — #120: added the sidewall-elongation causal graph, every edge carrying a verbatim quotation from open-access full text. Reading the sources reversed the causality the issue proposed: #120 described MreB filaments moving and carrying the synthases, but Typas et al. 2011 report that depleting the elongation transpeptidase abolishes filament movement, so peptidoglycan synthesis is the motor and the filament steers it. #161: the RodA component cited Shi et al. 2018 and Typas et al. 2011, neither of which contains the strings RodA or SEDS -- RodA was shown to be the polymerase in 2016, five years after Typas. Both notes are replaced by Meeske et al. 2016 with verbatim support.
2026-09-02T23:48:58Z claude · OPEN_DISCUSSION — #161: flagged that definition_source (Typas et al. 2011) predates the RodA/SEDS finding the definition asserts. The component evidence is corrected; rewording the definition is left to a curator.
2026-09-02T23:56:08Z claude · NORMALISE_NODE_REFERENCE — Self-review: the MreB node used xrefs where every other STRUCTURE node in the corpus uses grounding. xrefs asserts equivalence -- the misuse #119 removed from the MreB / elongasome pair -- while grounding names what the node denotes, which is what was meant.
2026-09-02T23:57:26Z claude · STRENGTHEN_EDGE_EVIDENCE — Self-review: the pg_synthesis drives complex_motion edge rested on a sentence about comparable velocities, which shows coupling rather than direction. The depletion result -- stopping synthesis stops the movement -- is what supports 'drives', so it now leads the evidence and the velocity observation is labelled for what it shows.
2026-09-08T07:39:02Z uniprot_genes · SEED_PROTEIN_EXAMPLES — #183: added 5 protein example(s) by resolving each of the component's declared gene symbols to the single reviewed UniProtKB entry for that symbol in a taxon this record names, deduplicated by accession. Symbols resolving to more than one reviewed entry were skipped rather than chosen between.
2026-10-05T17:45:01Z codex · ADD_PATHWAY_LINK — Added an evidence-backed, organism-scoped PathwayMech link with a full source commit and explicit relation limits.
2026-10-12T06:20:01Z codex · ADDRESS_SAVED_REVIEW — Addressed 20261012T061610Z-elongasome-evidence-review: elongasome-definition-source-residual; elongasome-wall-parthood; elongasome-motion-and-shape-scope; elongasome-archaeal-negative-evidence. Corrected evidence scope and mechanism claims using inspected sources. Original history/rationale and posed dates remain intact; source discrepancies are explicitly retained.
2026-10-12T06:32:01Z codex · CORRECT_RESOLVED_DISCUSSION_PROMPT — Complete rendered acceptance for 20261012T061610Z-elongasome-evidence-review F1: replace the unchanged false premise in the visible resolved-discussion prompt. The template does not display resolution_note. Preserve original rationale, posed date and all previous history; the pre-edit prompt remains in Git and the immutable observation.

Source: data/structures/division_machinery/elongasome.yaml