Regulation of functions of RecA protein by the conformational change

纯化的RecA蛋白可以在体外切割LexA蛋白和几个噬菌体抑制物(&lt；lambda&gt；，P22和434)，在这些多肽链的中间有一个特定的Ala-Gly多肽键。这个反应需要单链脱氧核糖核酸、三磷酸腺苷(或三磷酸腺苷；-S或d三磷酸腺苷)和镁^()。为了了解RecA蛋白的激活形式是什么以及切割特异性是如何确定的，我们使用&lt；Phi&gt；80，&lt；lambda&gt；和LexA阻遏物和RecA突变蛋白研究了切割反应的详细机制。结果表明，RecA介导的抑制子的切割反应受两个过程控制。其一是RecA蛋白与单链DNA之间形成活性的二元复合体。另一类是活性二元复合体与阻遏蛋白的相互作用。前者可能由RecA蛋白的C-末端区域控制，后者可能受阻遏因子与特定辅因子如dGpG或DAPG相互作用引起的构象变化的刺激。

Purified RecA protein can cleave LexA protein and several prophage repressors ( <lambda> , P22 and 434 ) in vitro at a specific Ala-Gly peptide bonds in the middle of these polypeptide chains. This reaction requires single-stranded DNA, ATP (or ATP- <gamma> -S or dATP) and <Mg^(++)> . To learn what the activated form of RecA protein is and how the cleavage specificity is determined, we investigated the detail mechanisms on the cleavage reaction using <phi> 80, <lambda> and LexA repressors and RecA mutant proteins. Results showed that the RecA-mediated cleavage reaction of the repressors was controled with two processes. One is the formation of an active binary complex between RecA protein and single-stranded DNA. Another is the interaction of the active binary complex with repressor protein. The former process is likely to be controled by the C-terminal region of RecA protein, and the latter process seems to be stimulated by the conformational change of the repressor by interaction with a specific cofactor, such as dGpG or dApG.