DNA polymerase III, beta sliding clamp, central (IPR022637)

Short name: DNA_polIII_beta_cen

Overlapping homologous superfamilies


Domain relationships



DNA polymerase III is a complex, multichain holoenzyme responsible for most of the replicative synthesis in bacteria [PMID: 8548826]. It functions by adding nucleotide triphosphate (dNTP) residues to the 5'-end of a growing DNA chain, using a complementary DNA as template. The elongation factor beta-clamp, also called beta subunit, is part of the DNA polymerase III holoenzyme. However, beta-clamp is not attached to polymerase III permanently like the other subunits. It is loaded on the DNA, by clamp loader, a subunit of DNA Pol III [PMID: 27499105].

The beta clamp forms a ring shaped dimer that encircles dsDNA (sliding clamp) in bacteria. The bacterial beta clamp is a homodimer; each monomer consists of three globular domains to yield a six-domain ring [PMID: 18191219]. It is structurally similar to the trimeric ring formed by proliferating cell nuclear antigen (PCNA) (found in eukaryotes and archaea) and the processivity factor (found in bacteriophages T4 and RB69) [PMID: 1358275]. This structural correspondence further substantiates the mechanistic connection between eukaryotic and prokaryotic DNA replication that has been suggested on biochemical grounds.

This entry describes the central domain of the beta sliding clamp.

GO terms

Biological Process

GO:0006260 DNA replication

Molecular Function

GO:0008408 3'-5' exonuclease activity
GO:0003887 DNA-directed DNA polymerase activity

Cellular Component

GO:0009360 DNA polymerase III complex

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.