Soltis D A, Lehman I R
J Biol Chem. 1983 May 25;258(10):6073-7.
recA protein and circular single-stranded DNA form a stable complex in the presence of single-stranded DNA binding protein (SSB), in which one recA protein monomer is bound per two nucleotides of DNA. These complexes are kinetically significant intermediates in the exchange of strands between the single-stranded DNA and an homologous linear duplex. After completion of strand exchange, the recA protein remains tightly associated with the circular duplex product of the reaction and the SSB is bound to the displaced linear single strand. Upon addition of ADP, the recA protein-duplex DNA complex dissociates. RecA protein also interacts with single-stranded DNA in the absence of SSB; however, the amount of recA protein bound is substantially reduced. These findings provide direct physical evidence for the participation of SSB in the formation of the recA protein-single-stranded DNA complexes inferred earlier from kinetic analysis. Moreover, they confirm the ability of recA protein to equilibrate between bound and free forms in the absence of SSB.
在单链DNA结合蛋白（SSB）存在的情况下，RecA蛋白与环状单链DNA形成稳定的复合物，其中每两个核苷酸的DNA结合一个RecA蛋白单体。这些复合物是单链DNA与同源线性双链之间链交换的动力学重要中间体。链交换完成后，RecA蛋白仍与反应的环状双链产物紧密结合，而SSB则与被置换的线性单链结合。加入ADP后，RecA蛋白 - 双链DNA复合物解离。在没有SSB的情况下，RecA蛋白也与单链DNA相互作用；然而，结合的RecA蛋白量大幅减少。这些发现为SSB参与早期从动力学分析推断出的RecA蛋白 - 单链DNA复合物的形成提供了直接的物理证据。此外，它们证实了RecA蛋白在没有SSB的情况下在结合和游离形式之间平衡的能力。
