Department of Medicine and Cellular, Cancer Center, Ludwig Institute for Cancer Research, University of California San Diego School of Medicine, La Jolla, California 92093-0669, USA.
J Biol Chem. 2010 Mar 19;285(12):9301-10. doi: 10.1074/jbc.M109.096388. Epub 2010 Jan 20.
Indirect evidence has suggested that the Msh2-Msh6 mispair-binding complex undergoes conformational changes upon binding of ATP and mispairs, resulting in the formation of Msh2-Msh6 sliding clamps and licensing the formation of Msh2-Msh6-Mlh1-Pms1 ternary complexes. Here, we have studied eight mutant Msh2-Msh6 complexes with defective responses to nucleotide binding and/or mispair binding and used them to study the conformational changes required for sliding clamp formation and ternary complex assembly. ATP binding to the Msh6 nucleotide-binding site results in a conformational change that allows binding of ATP to the Msh2 nucleotide-binding site, although ATP binding to the two nucleotide-binding sites appears to be uncoupled in some mutant complexes. The formation of Msh2-Msh6-Mlh1-Pms1 ternary complexes requires ATP binding to only the Msh6 nucleotide-binding site, whereas the formation of Msh2-Msh6 sliding clamps requires ATP binding to both the Msh2 and Msh6 nucleotide-binding sites. In addition, the properties of the different mutant complexes suggest that distinct conformational states mediated by communication between the Msh2 and Msh6 nucleotide-binding sites are required for the formation of ternary complexes and sliding clamps.
间接证据表明，Msh2-Msh6 错配结合复合物在结合 ATP 和错配时会发生构象变化，导致 Msh2-Msh6 滑动夹子的形成，并允许 Msh2-Msh6-Mlh1-Pms1 三元复合物的形成。在这里，我们研究了八个具有缺陷核苷酸结合和/或错配结合反应的突变 Msh2-Msh6 复合物，并利用它们来研究形成滑动夹子和三元复合物组装所需的构象变化。ATP 结合到 Msh6 的核苷酸结合位点会导致构象变化，从而允许 ATP 结合到 Msh2 的核苷酸结合位点，尽管在一些突变复合物中，ATP 似乎与两个核苷酸结合位点的结合是解偶联的。Msh2-Msh6-Mlh1-Pms1 三元复合物的形成仅需要 ATP 结合到 Msh6 的核苷酸结合位点，而 Msh2-Msh6 滑动夹子的形成则需要 ATP 结合到 Msh2 和 Msh6 的核苷酸结合位点。此外，不同突变复合物的特性表明，形成三元复合物和滑动夹子需要 Msh2 和 Msh6 核苷酸结合位点之间的通讯介导的不同构象状态。
