Figure 5.
A role for δ-W279 in clamp loader function during DNA replication. Extension of 5′ 32P-labeled 30-nt primer on a 105-nt template by E. coli Pol III core polymerase in the presence of wild-type and mutant clamp loaders, at different NaCl concentrations. Reactions containing p/tDNA, SSB, ATP, β and dNTPs were initiated with core polymerase in the absence of clamp loader (lane 1) or with the clamp loader, and DNA products analyzed on a denaturing gel. Reactions containing γ complex (lanes 2 and 5), δW279A-γ complex (lanes 3 and 6) and δW279Y-γ complex (lanes 4 and 7) reveal loss of processive DNA replication with the mutant δW279A-γ complex at 100 mM NaCl. The markers are 32P-labeled 30- and 81-nt DNAs.