DNA polymerase III, beta sliding clamp processivity factor complex

GO:0044775 · Other · Multiprotein complex · Proposed

A subcomplex of the DNA polymerase III holoenzyme which is responsible for tethering the catalytic subunit of DNA polymerase to DNA during high-speed replication. The complex is homodimeric in prokaryotes, and homotrimeric in other species. [GO:0044775]

Part of: DNA polymerase III complex (GO:0009360)

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
DNA polymerase III beta subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	dnaN	two copies per prokaryotic clamp ring	UNKNOWN	Ring-forming beta subunit that dimerizes to make the prokaryotic DNA polymerase III sliding clamp. `GO:0044775` GO:0044775 defines the beta sliding-clamp processivity factor complex as homodimeric in prokaryotes. `PMID:1349852` Kong et al. 1992 solved the E. coli DNA polymerase III beta subunit crystal structure and described a beta-subunit dimer forming a ring-shaped structure that can encircle duplex DNA. `UniProtKB:P0A988` UniProtKB P0A988 is the reviewed Escherichia coli K-12 dnaN entry for the beta sliding clamp.

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.

DNA polymerase III beta subunit

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P0A988`	Beta sliding clamp	dnaN	Escherichia coli K-12 (`NCBITaxon:83333`)	REVIEWED
Role and evidence (1 reference) Reviewed E. coli K-12 DnaN accession for the DNA polymerase III beta sliding-clamp subunit. `UniProtKB:P0A988` UniProtKB P0A988 is the reviewed Escherichia coli K-12 dnaN entry for the beta sliding clamp.

Canonical examples

NCBITaxon:562 Escherichia coli — Species source for the DNA polymerase III beta-subunit crystal structure used to establish the ring-shaped beta sliding clamp. [PMID:1349852]

Functions

DNA replication GO:0006260 — The DNA polymerase III beta clamp supports processive DNA replication by tethering the Pol III catalytic core to DNA.
- GO:0044775 GO:0044775 defines the beta sliding-clamp complex by its responsibility for tethering the catalytic subunit of DNA polymerase to DNA during high-speed replication.
- GO:0006260 GO:0006260 is the Gene Ontology biological-process term for DNA replication.

Mechanism graphs

Beta sliding clamp tethers DNA polymerase III to DNA (FUNCTION)

The DnaN beta subunit dimer forms the beta sliding clamp that encircles duplex DNA and tethers the Pol III core during processive DNA replication.

Subject	Predicate	Object	Evidence
DNA polymerase III beta subunit	is part of	DNA polymerase III, beta sliding clamp processivity factor complex	`PMID:1349852` Kong et al. 1992 reported that a dimer of the E. coli beta subunit forms a ring-shaped structure. `GO:0044775` GO:0044775 defines the beta sliding-clamp complex as homodimeric in prokaryotes.
DNA polymerase III, beta sliding clamp processivity factor complex	encircles	duplex DNA	`PMID:1349852` The E. coli beta-subunit dimer crystal structure forms a ring lined by alpha helices that can encircle duplex DNA.
DNA polymerase III, beta sliding clamp processivity factor complex	tethers	DNA polymerase III, core complex	`GO:0044775` GO:0044775 defines the beta sliding-clamp complex by its responsibility for tethering the catalytic subunit of DNA polymerase to DNA.
DNA polymerase III, beta sliding clamp processivity factor complex	supports	DNA replication	`GO:0044775` GO:0044775 places the beta sliding clamp within the DNA polymerase III holoenzyme during high-speed DNA replication. `GO:0006260` GO:0006260 defines the DNA replication biological process.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral DnaN/beta sliding-clamp family grounding for the DNA polymerase III beta-clamp component. This first GO:0044775 split captures the E. coli beta subunit from beta-clamp structure literature and the dnaN gene symbol from reviewed UniProtKB:P0A988 while leaving exact source-neutral protein-family grounding to a later pass.

Evidence

GO:0044775 Gene Ontology cellular-component term for the DNA polymerase III beta sliding-clamp processivity factor complex.
GO:0032991 Gene Ontology cellular-component parent term for protein-containing complexes.
GO:0009360 Gene Ontology cellular-component term for the DNA polymerase III holoenzyme complex that contains the beta sliding clamp.
GO:0044776 Gene Ontology cellular-component term for the Pol III core that is tethered by the beta sliding clamp.
GO:0006260 Gene Ontology biological-process term for DNA replication.
PMID:1349852 PubMed identifier for Kong, Onrust, O'Donnell and Kuriyan 1992, Three-dimensional structure of the beta subunit of E. coli DNA polymerase III holoenzyme: a sliding DNA clamp.
DOI:10.1016/0092-8674(92)90445-i DOI for Kong et al. 1992 as reported by PubMed.
UniProtKB:P0A988 Reviewed UniProtKB accession for the Escherichia coli K-12 DnaN beta sliding-clamp protein example.

Curation history

2026-09-28T10:08:14Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-28T10:09:06Z codex · EXPANDED_RECORD — Added protein-containing-complex parentage, DNA polymerase III holoenzyme parthood, a label-only dnaN beta-subunit component, an E. coli canonical example, DNA-replication function evidence, GO/PubMed evidence, a nonmechanistic beta-clamp graph, and a DnaN-grounding TODO.
2026-09-28T10:11:18Z codex · ADD_PROTEIN_EXAMPLE — Added reviewed UniProtKB:P0A988 as the taxon-specific E. coli K-12 DnaN beta-clamp example and cited it for the component gene symbol.
2026-09-28T10:24:35Z codex · FIX_REVIEW_ISSUE — Fixed #1716 by attributing the discussion's dnaN gene-symbol support to UniProtKB:P0A988.

Source: data/structures/other/dna_polymerase_iii_beta_sliding_clamp_processivity_factor_complex.yaml