Lindsley J E, Cox M M
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706.
J Biol Chem. 1990 Jun 15;265(17):10164-71.
The recA protein from Escherichia coli can homologously align two duplex DNA molecules; however, this interaction is much less efficient than the alignment of a single strand and a duplex. Three strand paranemic joints are readily detected. In contrast, duplex-duplex pairing is detected only when the incoming (second) duplex is negatively supercoiled, and even here the pairing is inefficient. The recA protein-promoted four strand exchange reaction is initiated in a three strand region, with efficiency increasing with the length of potential three strand pairing available for initiation. This indicates that a paranemic joint involving three DNA strands may be an important intermediate in all recA protein-mediated DNA strand exchange reactions and that the presence of three strands rather than four is a fundamental structural parameter of paranemic joints.
来自大肠杆菌的RecA蛋白能够使两个双链DNA分子进行同源配对；然而，这种相互作用的效率远低于单链与双链的配对。三链平行配对接头很容易被检测到。相比之下，只有当进入的（第二条）双链处于负超螺旋状态时，双链-双链配对才能被检测到，即便如此，这种配对效率也很低。RecA蛋白促进的四链交换反应在一个三链区域启动，其效率随着可用于起始的潜在三链配对长度的增加而提高。这表明涉及三条DNA链的平行配对接头可能是所有RecA蛋白介导的DNA链交换反应中的一个重要中间体，并且三条链而非四条链的存在是平行配对接头的一个基本结构参数。
