Temporal correlation of DNA binding, ATP hydrolysis, and clamp release in the clamp loading reaction catalyzed by the Escherichia coli gamma complex.

ABSTRACT: Clamp loaders are multisubunit complexes that use the energy derived from ATP binding and hydrolysis to assemble ring-shaped sliding clamps onto DNA. Sliding clamps in turn tether DNA polymerases to the templates being copied to increase the processivity of DNA synthesis. Here, the rate of clamp release during the clamp loading reaction was measured directly for the first time using a FRET-based assay in which the E. coli gamma complex clamp loader (gamma3deltadelta'chipsi) was labeled with a fluorescent donor, and the beta-clamp was labeled with a nonfluorescent quencher. When a beta.gamma complex is added to DNA, there is a significant time lag before the clamp is released onto DNA. To establish what events take place during this time lag, the timing of clamp release was compared to the

SUBMITTER: Anderson SG 

PROVIDER: S-EPMC2759312 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature