Confers DNA tethering and processivity to DNA polymerases and other proteins. Acts as a clamp, forming a ring around DNA (a reaction catalyzed by the clamp-loading complex) which diffuses in an ATP-independent manner freely and bidirectionally along dsDNA (PubMed:2040637). DNA bound in the ring is bent 22 degrees, in solution primed DNA is bound more tightly than dsDNA, suggesting the clamp binds both ss- and dsDNA (PubMed:18191219). In a complex of DNA with this protein, alpha, epsilon and tau subunits however the DNA is only slightly bent (PubMed:26499492). Coordinates protein traffic at the replication fork, where it interacts with multiple DNA polymerases, repair factors and other proteins (PubMed:15466025, PubMed:16168375, PubMed:22716942, PubMed:14592985, PubMed:14729336, PubMed:26499492, PubMed:15952889). Initially characterized for its ability to contact the alpha subunit (dnaE) of DNA polymerase III (Pol III), tethering it to the DNA and conferring very high processivity (PubMed:2040637). Pol III is a complex, multichain enzyme responsible for most of the replicative synthesis in bacteria; it also exhibits 3'-5' exonuclease proofreading activity. The beta chain is required for initiation of replication as well as for processivity of DNA replication (PubMed:3519609, PubMed:2040637). A single clamp can bind both Pol III and IV, allowing the repair Pol IV to access DNA when it is damaged and needs to be fixed, a process the replicative polymerase cannot perform; when DNA is repaired Pol III takes over again (PubMed:16168375). Serves as a processivity factor for DNA polymerases II (PubMed:1999435, PubMed:1534562), IV (PubMed:10801133) and V (PubMed:10801133). A shorter protein beta* may be important for increasing survival after UV irradiation, and stimulates DNA synthesis with increased processivity in the presence of core Pol III plus the clamp loader complex (PubMed:8576210, PubMed:8576212).