DNA polymerase III is a complex, multichain enzyme responsible for most of the replicative synthesis in bacteria. This DNA polymerase also exhibits 3' to 5' exonuclease activity. The alpha chain is the DNA polymerase (By similarity). a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) DNA polymerase III contains a core (composed of alpha, epsilon and theta chains) that associates with a tau subunit. This core dimerizes to form the PolIII' complex. PolIII' associates with the gamma complex (composed of gamma, delta, delta', psi and chi chains) and with the beta chain to form the complete DNA polymerase III complex (By similarity). This protein undergoes a protein self splicing that involves a post-translational excision of the intervening region (intein) followed by peptide ligation. The intein is a split intein capable of protein trans-splicing. The N- and C-terminal halves of dnaE are encoded by two separate genes located 745 kb apart in the genome and on opposite DNA strands. The dnaE-N product consists of a N-extein sequence followed by a 123-aa intein sequence (Ssp dnaE1), whereas the dnaE-C product consists of a 36-aa intein sequence (Ssp dnaE2) followed by a C-extein sequence. The N- and C-extein sequences together reconstitute a complete DnaE sequence that is interrupted by the intein sequences inside the beta- and tau-binding domains. Belongs to the DNA polymerase type-C family. DnaE subfamily.