A DNA pairing-enhanced conformation of bacterial RecA proteins
A DNA pairing-enhanced conformation of bacterial RecA proteins
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DOI：
10.1074/jbc.m308563200
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发表时间：
2003-12-26
影响因子：
4.8
通讯作者：
Cox, MM
中科院分区：
文献类型：
--
作者：
Haruta, N;Yu, XN;Cox, MM
大肠杆菌 (Ec) 和耐辐射奇球菌 (Dr) 的 RecA 蛋白均促进涉及两个双链 DNA 的 DNA 链交换反应。 DrRecA蛋白促进的四链交换反应与EcRecA促进的四链交换反应类似，只是该反应的关键部分被Ec单链DNA结合蛋白(SSB)抑制。在不存在 SSB 的情况下，DNA 缺口末端的 dsDNA-ssDNA 连接大大增强了链交换的启动。 EcRecA 蛋白也呈现出同样的趋势。这些结果导致已发表的关于 RecA 介导的 DNA 配对途径的假设得到扩展，其中缓慢的一级步骤（在几项研究中观察到）涉及到我们指定的 P 状态的结构转变。P 状态与 RecA 与双链 (ds) DNA 结合时发现的状态相同。当 RecA 蛋白与单链 (ss) DNA 结合时出现的结构状态被指定为 A。DNA 配对模型反过来又促进了目前工作中得出的三个附加结论的阐明。 1) 当与 ssDNA 结合的 RecA 细丝片段被迫进入 P 状态时（因为 RecA 与紧邻 dsDNA-ssDNA 连接的 ssDNA 结合），该片段变得“配对增强”。 2) D. radiodurans RecA 蛋白不寻常的 DNA 配对特性可以通过假设该蛋白对从 P 状态启动 DNA 链交换有更严格的要求来解释。 3) 与 dsDNA 结合的 RecA 丝（P 状态）相对于与 ssDNA 结合的 RecA 丝（A 状态）具有直接可观察到的结构变化，涉及 C 末端结构域。
The RecA proteins of Escherichia coli (Ec) and Deinococcus radiodurans (Dr) both promote a DNA strand exchange reaction involving two duplex DNAs. The four-strand exchange reaction promoted by the DrRecA protein is similar to that promoted by EcRecA, except that key parts of the reaction are inhibited by Ec single-stranded DNA-binding protein (SSB). In the absence of SSB, the initiation of strand exchange is greatly enhanced by dsDNA-ssDNA junctions at the ends of DNA gaps. This same trend is seen with the EcRecA protein. The results lead to an expansion of published hypotheses for the pathway for RecA-mediated DNA pairing, in which the slow first order step (observed in several studies) involves a structural transition to a state we designate P. The P state is identical to the state found when RecA is bound to double-stranded (ds) DNA. The structural state present when the RecA protein is bound to single-stranded (ss) DNA is designated A. The DNA pairing model in turn facilitates an articulation of three additional conclusions arising from the present work. 1) When a segment of a RecA filament bound to ssDNA is forced into the P state (as RecA bound to the ssDNA immediately adjacent to dsDNA-ssDNA junction), the segment becomes "pairing enhanced." 2) The unusual DNA pairing properties of the D. radiodurans RecA protein can be explained by postulating this protein has a more stringent requirement to initiate DNA strand exchange from the P state. 3) RecA filaments bound to dsDNA (P state) have directly observable structural changes relative to RecA filaments bound to ssDNA (A state), involving the C-terminal domain.