Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Box 8231, St. Louis, MO 63110, United States.
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Box 8231, St. Louis, MO 63110, United States.
J Mol Biol. 2018 Oct 19;430(21):4260-4274. doi: 10.1016/j.jmb.2018.08.022. Epub 2018 Aug 30.
Escherichia coli UvrD is a superfamily 1 helicase/translocase involved in multiple DNA metabolic processes including methyl-directed mismatch DNA repair. Although a UvrD monomer can translocate along single-stranded DNA, a UvrD dimer is needed for processive helicase activity in vitro. E. coli MutL, a regulatory protein involved in methyl-directed mismatch repair, stimulates UvrD helicase activity; however, the mechanism is not well understood. Using single-molecule fluorescence and ensemble approaches, we find that a single MutL dimer can activate latent UvrD monomer helicase activity. However, we also find that MutL stimulates UvrD dimer helicase activity. We further find that MutL enhances the DNA-unwinding processivity of UvrD. Hence, MutL acts as a processivity factor by binding to and presumably moving along with UvrD to facilitate DNA unwinding.
大肠杆菌 UvrD 是一种超家族 1 解旋酶/移位酶，参与多种 DNA 代谢过程，包括甲基化指导的错配 DNA 修复。虽然 UvrD 单体可以沿单链 DNA 移位，但 UvrD 二聚体在体外进行连续解旋酶活性是必需的。大肠杆菌 MutL，一种参与甲基化指导的错配修复的调节蛋白，可刺激 UvrD 解旋酶活性；然而，其机制尚不清楚。我们使用单分子荧光和整体方法发现，单个 MutL 二聚体可以激活潜伏的 UvrD 单体解旋酶活性。然而，我们还发现 MutL 可刺激 UvrD 二聚体解旋酶活性。我们进一步发现 MutL 增强了 UvrD 的 DNA 解旋过程的持续性。因此，MutL 通过与 UvrD 结合并可能沿着 UvrD 移动来促进 DNA 解旋，从而充当持续性因子。
