The beta(2) clamp in the Mycobacterium tuberculosis DNA polymerase III alpha beta(2)epsilon replicase promotes polymerization and reduces exonuclease activity

摘要: DNA polymerase III (DNA pol III) is a multi-subunit replication machine responsible for the accurate and rapid replication of bacterial genomes, however, how it functions in Mycobacterium tuberculosis (Mtb) requires further investigation. We have reconstituted the leading-strand replication process of the Mtb DNA pol III holoenzyme in vitro, and investigated the physical and functional relationships between its key components. We verify the presence of an alpha beta(2)epsilon polymerase-clamp-exonuclease replicase complex by biochemical methods and protein-protein interaction assays in vitro and in vivo and confirm that, in addition to the polymerase activity of its a subunit, Mtb DNA pol III has two potential proofreading subunits; the alpha and epsilon subunits. During DNA replication, the presence of the beta(2) clamp strongly promotes the polymerization of the alpha beta(2)epsilon replicase and reduces its exonuclease activity. Our work provides a foundation for further research on the mechanism by which the replication machinery switches between replication and proofreading and provides an experimental platform for the selection of antimicrobials targeting DNA replication in Mtb.