ATP-induced dissociation and sliding clamp formation of MSH2-MSH6 from mismatched DNA. The interaction of 20 nM MSH2-MSH6 with mismatched (G:T) or homoduplex (G:C) DNA, having either free or α-digoxigenin blocked ends, was monitored by SPR. Binding of MSH2-MSH6 (A, C) and MSH2(NΔ25)-MSH6 (B, D) to DNA was recorded in the absence of ATP followed by a brief dissociation phase in buffer. When indicated, buffer was supplemented with 50 μM ATP (A, B) or 50 μM ATP along with 20 nM MSH2-MSH6 (C, D).