Binding of the regulatory domain of MutL to the sliding β-clamp is species specific
Binding of the regulatory domain of MutL to the sliding β-clamp is species specific
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DOI：
10.1093/nar/gkz115
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发表时间：
2019-05-21
影响因子：
14.9
通讯作者：
Guarne, Alba
中科院分区：
文献类型：
--
作者：
Almawi, Ahmad W.;Scotland, Michelle K.;Guarne, Alba
β-夹是DNA复制和分叉管理的核心蛋白质枢纽。与β-夹相互作用的蛋白质具有通常在延伸区域中发现的保守的夹结合基序。因此，钳相互作用已经-几乎排他地-使用短肽重演结合基序进行了研究。这种方法揭示了介导结合的分子决定簇，但无法描述如何识别嵌入结构域中的夹结合基序的蛋白质。错配修复蛋白MutL具有内部夹结合基序，但其与β-夹的相互作用取决于生物体而具有不同的作用。在枯草芽孢杆菌中，这种相互作用刺激MutL的核酸内切酶活性，并且对于DNA错配修复至关重要。相反，破坏大肠杆菌MutL和β-钳夹之间的相互作用仅导致轻度的突变子表型。在此，我们确定了E. coli和B. subtilis MutL与它们各自的β-夹结合。这些结构揭示了不同的结合模式，与作为两步过程的与β-钳的结合一致。功能表征表明，在调节结构域内，两种蛋白质之间的相互作用仅需要钳结合基序。然而，额外的图案以外的监管结构域可以稳定的相互作用。我们提出了一个模型的MutL在缺乏甲基指导的错配修复的生物体中的核酸内切酶活性的激活。
The beta-clamp is a protein hub central to DNA replication and fork management. Proteins interacting with the beta-clamp harbor a conserved clamp-binding motif that is often found in extended regions. Therefore, clamp interactions have -almost exclusively- been studied using short peptides recapitulating the binding motif. This approach has revealed the molecular determinants that mediate the binding but cannot describe how proteins with clamp-binding motifs embedded in structured domains are recognized. The mismatch repair protein MutL has an internal clamp-binding motif, but its interaction with the beta-clamp has different roles depending on the organism. In Bacillus subtilis, the interaction stimulates the endonuclease activity of MutL and it is critical for DNA mismatch repair. Conversely, disrupting the interaction between Escherichia coli MutL and the beta-clamp only causes a mild mutator phenotype. Here, we determined the structures of the regulatory domains of E. coli and B. subtilis MutL bound to their respective beta-clamps. The structures reveal different binding modes consistent with the binding to the beta-clamp being a two-step process. Functional characterization indicates that, within the regulatory domain, only the clamp binding motif is required for the interaction between the two proteins. However, additional motifs beyond the regulatory domain may stabilize the interaction. We propose a model for the activation of the endonuclease activity of MutL in organisms lacking methyl-directed mismatch repair.