Cox M M
Department of Biochemistry, University of Wisconsin-Madison 53706.
Mol Microbiol. 1991 Jun;5(6):1295-9. doi: 10.1111/j.1365-2958.1991.tb00775.x.
The Escherichia coli RecA protein plays a central role in homologous genetic recombination, recombinational repair, and several other processes in bacteria. In vitro, an extended filament involving thousands of RecA monomers promotes a reaction in which individual DNA strands switch pairing partners (DNA strand exchange). This reaction has been extensively studied as a paradigm for the central steps in recombination. Because the strand-exchange reaction is relatively simple and isoenergetic, the complexity of the RecA system that carries it out has led to controversy about the functional significance of many fundamental properties of RecA. Filamentous protein structures involving thousands of RecA monomers, which hydrolyse 100 ATPs per base pair of heteroduplex DNA formed, are hard to rationalize in the context of recombination between two homologous DNAs. The thermodynamic barriers to strand exchange are much too small. These molecular features of the system can be easily rationalized, however, by shifting the focus to DNA repair.
大肠杆菌RecA蛋白在细菌的同源基因重组、重组修复及其他几个过程中起着核心作用。在体外，由数千个RecA单体组成的延伸丝促进了一个反应，即单条DNA链切换配对伙伴（DNA链交换）。作为重组核心步骤的范例，该反应已得到广泛研究。由于链交换反应相对简单且等能，执行该反应的RecA系统的复杂性引发了关于RecA许多基本特性功能意义的争议。涉及数千个RecA单体的丝状蛋白结构，每形成一对异源双链DNA碱基对就水解100个ATP，在两个同源DNA重组的背景下很难解释其合理性。链交换的热力学障碍太小。然而，通过将重点转移到DNA修复上，该系统的这些分子特征就很容易解释了。
