ATP hydrolysis-dependent formation of a dynamic ternary nucleoprotein complex with MutS and MutL

Functional interactions of Escherichia coli MutS and MutL in mismatch repai r are dependent on ATP, In this study, we show that MutS and MutL associate with immobilised DNA in a manner dependent on AIP hydrolysis and with an A TP concentration near the solution K-m of the ATPase of MutS, After removal of MutS, MutL and ATP, much of the protein in this ternary complex is not stably associated, with MutL leaving the complex more rapidly than MutS, Th e rapid dissociation reveals a dynamic interaction with concurrent rapid as sociation and dissociation of proteins from the DNA, Analysis by surface pl asmon resonance showed that the DNA interacting with dynamically bound prot ein was more resistant to nuclease digestion than the DNA in MutS-DNA compl exes. Nonhydrolysable analogs of ATP inhibit the formation of this dynamic complex, but permit formation of a second type of ternary complex with MutS and MutL stably bound to the immobilised DNA.