McrBs，一种用于McrBC活性的调节肽。
McrBs, a modulator peptide for McrBC activity.
作者信息
Panne D, Raleigh E A, Bickle T A
机构信息
Department of Microbiology, Biozentrum, Basel University, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
出版信息
EMBO J. 1998 Sep 15;17(18):5477-83. doi: 10.1093/emboj/17.18.5477.
McrBC is a methylation-dependent endonuclease from Escherichia coli K-12. The enzyme recognizes DNA with modified cytosines preceded by a purine. McrBC restricts DNA that contains at least two methylated recognition sites separated by 40-80 bp. Two gene products, McrBL and McrBs, are produced from the mcrB gene and one, McrC, from the mcrC gene. DNA cleavage in vitro requires McrBL, McrC, GTP and Mg2+. We found that DNA cleavage was optimal at a ratio of 3-5 McrBL per molecule of McrC, suggesting that formation of a multisubunit complex with several molecules of McrBL is required for cleavage. To understand the role of McrBs, we have purified the protein and analyzed its role in vitro. At the optimal ratio of 3-5 McrBL per molecule of McrC, McrBs acted as an inhibitor of DNA cleavage. Inhibition was due to sequestration of McrC and required the presence of GTP, suggesting that the interaction is GTP dependent. If McrC was in excess, a condition resulting in suboptimal DNA cleavage, addition of McrBs enhanced DNA cleavage, presumably due to sequestration of excess McrC. We suggest that the role of McrBs is to modulate McrBC activity by binding to McrC.
McrBC是一种来自大肠杆菌K-12的依赖甲基化的内切核酸酶。该酶识别在嘌呤之前含有修饰胞嘧啶的DNA。McrBC会限制含有至少两个被40-80个碱基对隔开的甲基化识别位点的DNA。mcrB基因产生两种基因产物，即McrBL和McrBs，mcrC基因产生一种产物，即McrC。体外DNA切割需要McrBL、McrC、GTP和Mg2+。我们发现，每分子McrC含有3-5个McrBL时，DNA切割效果最佳，这表明切割需要形成含有几个McrBL分子的多亚基复合物。为了了解McrBs的作用，我们纯化了该蛋白并分析了其在体外的作用。在每分子McrC含有3-5个McrBL的最佳比例下，McrBs作为DNA切割的抑制剂。抑制作用是由于McrC的隔离，并且需要GTP的存在，这表明这种相互作用依赖于GTP。如果McrC过量，导致DNA切割效果不理想，添加McrBs会增强DNA切割，可能是由于隔离了过量的McrC。我们认为McrBs的作用是通过与McrC结合来调节McrBC的活性。
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