Steady-state ATPase activity of E. coli MutS modulated by its dissociation from heteroduplex DNA |
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Authors: | Heo Seong-Dal Cho Minseon Ku Ja Kang Ban Changill |
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Institution: | Department of Chemistry, Pohang University of Science and Technology, San 31, Hyoja-Dong, Pohang, Gyungbuk 790-784, Republic of Korea |
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Abstract: | The ability of MutS to recognize mismatched DNA is required to initiate a mismatch repair (MMR) system. ATP binding and hydrolysis are essential in this process, but their role in MMR is still not fully understood. In this study, steady-state ATPase activities of MutS from Escherichia coli were investigated using the spectrophotometric method with a double end-blocked heteroduplex containing gapped bases. The ATPase activities of MutS increased as the number of gapped bases increased in a double end-blocked heteroduplex with 2-8 gapped bases in the chain, indicating that MutS dissociates from DNA when it reaches a scission during movement along the DNA. Since movement of MutS along the chain does not require extensive ATP hydrolysis and the ATPase activity is only enhanced when MutS dissociates from a heteroduplex, these results support the sliding clamp model in which ATP binding by MutS induces the formation of a hydrolysis-independent sliding clamp. |
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Keywords: | MutS Steady-state ATPase activity Spectrophotometric method Double end-blocked heteroduplex Gapped DNA |
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