Fig. 5.

Binding of Pol IV at a secondary site on β reduces the Pol III processivity. (A) The Pol III processivity decreases with increasing concentrations of Pol IV (●) but is unaffected by Pol IV^C, a mutant lacking its CBM (▲). (B) Reduction in the Pol III processivity with β^WT (black bars) also occurs with the single-cleft mutant clamp β⁺/β^C (gray bars; NS) but is partially alleviated by β^R, a clamp with a weakened Pol IV-interacting rim interface (cross-hatched bars; P < 0.01). N ranges from 71 to 470 for A and B, respectively. Values represent means ± SEMs.