Kodadek T, Alberts B M
Nature. 1987;326(6110):312-4. doi: 10.1038/326312a0.
The protein-mediated exchange of strands between a DNA double helix and a homologous DNA single strand involves both synapsis and branch migration, which are two important aspects of any general recombination reaction. Purified DNA-dependent ATPases from Escherichia coli (recA protein), Ustilago (rec 1 protein) and phage T4 (uvsX protein) have been shown to drive both synapsis and branch migration in vitro. The T4 gene 32 protein is a helix-destabilizing protein that greatly stimulates uvsX-protein-catalysed synapsis, and the E. coli SSB (single-strand binding) protein stimulates the analogous recA-protein-mediated reaction to a lesser degree. One suspects that several other proteins also play a role in the strand exchange process. For example, a DNA helicase could in principle accelerate branch migration rates by helping to melt the helix at the branch point. The T4 dda protein is a DNA helicase that is required to move the T4 replication fork past DNA template-bound proteins in vitro. Previously, we have shown that the dda protein binds to a column that contains immobilized T4 uvsX protein. We show here that this helicase specifically stimulates the branch migration reaction that the uvsX protein catalyses as a central part of the genetic recombination process in a T4 bacteriophage-infected cell.
蛋白质介导的DNA双螺旋与同源DNA单链之间的链交换涉及联会和分支迁移，这是任何一般重组反应的两个重要方面。已证明从大肠杆菌（RecA蛋白）、黑粉菌（Rec1蛋白）和噬菌体T4（UvsX蛋白）中纯化的依赖DNA的ATP酶在体外驱动联会和分支迁移。T4基因32蛋白是一种螺旋不稳定蛋白，能极大地刺激UvsX蛋白催化的联会，而大肠杆菌单链结合（SSB）蛋白对类似的RecA蛋白介导的反应刺激程度较小。有人怀疑还有其他几种蛋白质也在链交换过程中起作用。例如，DNA解旋酶原则上可以通过帮助在分支点解开螺旋来加速分支迁移速率。T4 dda蛋白是一种DNA解旋酶，在体外将T4复制叉移过与DNA模板结合的蛋白质时是必需的。以前，我们已经表明dda蛋白与含有固定化T4 UvsX蛋白的柱子结合。我们在此表明，这种解旋酶特异性地刺激UvsX蛋白催化的分支迁移反应，该反应是T4噬菌体感染细胞中基因重组过程的核心部分。
