Tsang S S, Muniyappa K, Azhderian E, Gonda D K, Radding C M, Flory J, Chase J W
J Mol Biol. 1985 Sep 20;185(2):295-309. doi: 10.1016/0022-2836(85)90405-x.
recA protein promotes homologous pairing and strand exchange by an ordered reaction in which the protein first polymerizes on single-stranded DNA. This presynaptic intermediate, which can be formed either in the presence or absence of Escherichia coli single-stranded binding protein (SSB), has been isolated by gel filtration and characterized. At saturation, purified complexes contained one molecule of recA protein per 3.6 nucleotide residues of single-stranded DNA. Complexes that had been formed in the presence of SSB contained up to one molecule of SSB per 15 nucleotide residues, but the content of SSB in different preparations of isolated complexes appeared to be inversely related to the content of recA protein. Even when they have lost as much as a third of their recA protein, presynaptic complexes can retain activity, because the formation of stable joint molecules depends principally on the binding of recA protein to the single-stranded DNA in the localized region that corresponds to the end of the duplex substrate.
RecA蛋白通过一种有序反应促进同源配对和链交换，在该反应中，蛋白质首先在单链DNA上聚合。这种突触前中间体，无论有无大肠杆菌单链结合蛋白（SSB）都可以形成，已通过凝胶过滤分离并进行了表征。在饱和状态下，纯化的复合物中每3.6个单链DNA核苷酸残基含有一个RecA蛋白分子。在SSB存在下形成的复合物每15个核苷酸残基最多含有一个SSB分子，但在不同分离复合物制剂中SSB的含量似乎与RecA蛋白的含量呈负相关。即使突触前复合物失去了多达三分之一的RecA蛋白，它们仍可保留活性，因为稳定连接分子的形成主要取决于RecA蛋白与对应于双链体底物末端的局部区域中的单链DNA的结合。
