Temporal Correlation of DNA Binding, ATP Hydrolysis, and Clamp Release in the Clamp Loading Reaction Catalyzed by the Escherichia coli γ complex

摘要: Clamp loaders are multisubunit complexes that use the energy derived from ATP binding and hydrolysis to assemble ring-shaped sliding clamps onto DNA. Sliding in turn tether DNA polymerases templates being copied increase processivity of synthesis. Here, rate clamp release during loading reaction was measured directly for first time using a FRET-based assay which E. coli γ complex loader (γ3δδ′χψ) labeled with fluorescent donor, β-clamp nonfluorescent quencher. When β·γ is added DNA, there significant lag before released To establish what events take place this lag, timing compared by measuring these reactions side-by-side assays. relatively rapid triggers ATP. Both occur prior release. Interestingly, temporal correlati...