MutS mediates heteroduplex loop formation by a translocation mechanism
MutS mediates heteroduplex loop formation by a translocation mechanism
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DOI：
10.1093/emboj/16.14.4467
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发表时间：
1997-07-16
期刊：
影响因子：
11.4
通讯作者：
Griffith, JD
中科院分区：
文献类型：
--
作者：
Allen, DJ;Makhov, A;Griffith, JD
大肠杆菌 MutS 和 MutL 与异源双链 DNA 的相互作用已通过电子显微镜观察到。在依赖于 ATP 水解的反应中，MutS 二聚体和 DNA 异源双链体之间的复合物转化为蛋白质稳定的 α 形环结构，在大多数情况下，错配位于 DNA 环内。环的形成取决于 ATP 水解，环大小随时间线性增加，磷酸盐缓冲液中的速率为 370 个碱基对/分钟，修复测定所用的 HEPES 缓冲液中的速率为约 10 000 个碱基对/分钟。这些观察结果表明了一种易位机制，其中与错配结合的 MutS 二聚体随后通过 ATP 依赖性跟踪或单维运动（在大多数情况下是从错配双向的）离开该位点。鉴于甲基定向途径的双向能力，该反应可能在异源双链体方向的确定中发挥作用。 MutL 增强了 MutS 介导的 DNA 环生长速率，并且当两种蛋白质都存在时，两者都位于 α 环结构的底部，并且两者都可以与反应后期产生的切除中间体保持关联。
Interaction of Escherichia coli MutS and MutL with heteroduplex DNA has been visualized by electron microscopy. In a reaction dependent on ATP hydrolysis, complexes between a MutS dimer and a DNA heteroduplex are converted to protein-stabilized, alpha-shaped loop structures with the mismatch in most cases located within the DNA loop, Loop formation depends on ATP hydrolysis and loop size increases linearly with time at a rate of 370 base pairs/min in phosphate buffer and about 10 000 base pairs/min in the HEPES buffer used for repair assay. These observations suggest a translocation mechanism in which a MutS dimer bound to a mismatch subsequently leaves this site by ATP-dependent tracking or unidimensional movement that is in most cases bidirectional from the mispair. In view of the bidirectional capability of the methyl-directed pathway, this reaction may play a role in determination of heteroduplex orientation. The rate of MutS-mediated DNA loop growth is enhanced by MutL, and when both proteins are present, both are found at the base of alpha-loop structures, and both can remain associated with excision intermediates produced in later stages of the reaction.