FIGURE 6.

T7 DNA polymerase rescues the DNA unwinding defect of A257T gp4. A, T7 DNAP and WT or A257T gp4 were assembled on the radiolabeled ds40 (20%) replication fork with dTTP. Unwinding reaction was initiated with MgCl₂. DNA unwinding proceeds either by both proteins moving together, forming a loop-like structure, or helicase moving alone. B, native polyacrylamide gels show the unwinding kinetics of WT and A257T gp4 in the presence and absence of T7 DNAP. C, unwinding kinetics by WT and A257T in the presence (open circles) and in the absence of T7 DNAP (filled circles) is shown. WT gp4 unwinds the forked substrate in the absence of T7 DNAP at ∼82 bp/s in the presence of T7 DNAP at ∼65 bp/s. The unwinding rate of A257T gp4 in the presence of T7 DNAP is ∼50 bp/s.