Beta clamp domain. The beta subunit (processivity factor) of DNA polymerase III holoenzyme, refered to as the beta clamp, forms a ring shaped dimer that encircles dsDNA (sliding clamp) in bacteria. The beta-clamp is structurally similar to the trimeric ring formed by PCNA (found in eukaryotes and archaea) and the processivity factor (found in bacteriophages T4 and RB69). This structural correspondence further substantiates the mechanistic connection between eukaryotic and prokaryotic DNA replication that has been suggested on biochemical grounds.
Jiyao W et al.(2023). "The conserved domain database in 2023.",