A slow ATP-induced conformational change limits the rate of DNA binding but not the rate of beta clamp binding by the escherichia coli gamma complex clamp loader.

ABSTRACT: In Escherichia coli, the gamma complex clamp loader loads the beta-sliding clamp onto DNA. The beta clamp tethers DNA polymerase III to DNA and enhances the efficiency of replication by increasing the processivity of DNA synthesis. In the presence of ATP, gamma complex binds beta and DNA to form a ternary complex. Binding to primed template DNA triggers gamma complex to hydrolyze ATP and release the clamp onto DNA. Here, we investigated the kinetics of forming a ternary complex by measuring rates of gamma complex binding beta and DNA. A fluorescence intensity-based beta binding assay was developed in which the fluorescence of pyrene covalently attached to beta increases when bound by gamma complex. Using this assay, an association rate constant of 2.3 x 10(7) m(-1) s(-1) for gamma complex

SUBMITTER: Thompson JA 

PROVIDER: S-EPMC2797285 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature