Regulation of functions of RecA protein by the conformational change

纯化的RecA蛋白在体外可<lambda>在这些多肽链中间的一个特异性Ala-Gly肽键上切割莱克萨蛋白和几种前噬菌体阻遏物（P22和434）。该反应需要单链DNA、ATP（或ATP-S<gamma>或dATP）和&lt;Mg^（++）&gt;。为了了解RecA蛋白的激活形式以及切割特异性是如何确定的，我们使用<phi>80<lambda>和莱克萨阻遏物和RecA突变蛋白研究了切割反应的详细机制。结果表明，RecA介导的阻遏物切割反应受两个过程控制。一个是RecA蛋白和单链DNA之间形成活性二元复合物。二是活性二元复合物与阻遏蛋白的相互作用。前一个过程可能受RecA蛋白C-末端区域的控制，后一个过程可能是由阻遏物与特定辅因子（如dGpG或dApG）相互作用而引起的构象变化所刺激的。

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.