Fig. 2. Inhibition of ATPase activity by AMPPNP. Competition of bound radiolabelled ADP with cold ATP or AMPPNP in (A) wild-type MutS and (B) R697A MutS. (C) Relative inhibition of ATPase activity by AMPPNP for wild-type and R697A MutS. The ATP concentration was kept constant, while the AMPPNP concentration was increased. Assay conditions were equal to those in (A) or (B).