Lloyd R G, Sharples G J
Department of Genetics, University of Nottingham, Queens Medical Centre, UK.
Nucleic Acids Res. 1993 Apr 25;21(8):1719-25. doi: 10.1093/nar/21.8.1719.
The RuvAB, RuvC and RecG proteins of Escherichia coli process intermediates in recombination and DNA repair into mature products. RuvAB and RecG catalyse branch migration of Holliday junctions, while RuvC resolves these structures by nuclease cleavage around the point of strand exchange. The overlap between RuvAB and RecG was investigated using synthetic X- and Y-junctions. RuvAB is a complex of RuvA and RuvB, with RuvA providing the DNA binding subunit and RuvB the ATPase activity that drives branch migration. Both RuvA and RecG form defined complexes with each of the junctions. The gel mobilities of these complexes suggests that the X-junction attracts two tetramers of RuvA, but mainly monomers of RecG. Dissociation of the junction in the presence of ATP requires high levels of RuvAB. RecG is shown to have a much higher specific activity to the extent that very little of this protein would be required to match RuvAB in vivo. Both proteins also dissociate a Y-junction, which is consistent with helicase activity. However, RecG shows no ability to unwind more conventional substrates and the suggestion is made that its helicase activity is directed towards specific DNA structures such as junctions.
大肠杆菌的RuvAB、RuvC和RecG蛋白在重组和DNA修复过程中处理中间体，使其成为成熟产物。RuvAB和RecG催化霍利迪连接体的分支迁移，而RuvC通过在链交换点周围进行核酸酶切割来解析这些结构。使用合成的X型和Y型连接体研究了RuvAB和RecG之间的重叠情况。RuvAB是RuvA和RuvB的复合物，其中RuvA提供DNA结合亚基，RuvB提供驱动分支迁移的ATP酶活性。RuvA和RecG都与每种连接体形成特定的复合物。这些复合物的凝胶迁移率表明，X型连接体吸引两个RuvA四聚体，但主要是RecG单体。在ATP存在的情况下，连接体的解离需要高水平的RuvAB。已证明RecG具有更高的比活性，以至于在体内只需极少量的这种蛋白质就能与RuvAB相匹配。这两种蛋白质也都能使Y型连接体解离，这与解旋酶活性一致。然而，RecG没有能力解开更传统的底物，有人提出其解旋酶活性针对特定的DNA结构，如连接体。
