Story R M, Steitz T A
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511.
Nature. 1992 Jan 23;355(6358):374-6. doi: 10.1038/355374a0.
The recA protein catalyses the ATP-driven homologous pairing and strand exchange of DNA molecules. It is an allosteric enzyme: the ATPase activity is DNA-dependent, and ATP-bound recA protein has a high affinity for DNA, whereas the ADP-bound form has a low affinity. In the absence of ATP hydrolysis, recA protein can still promote homologous pairing, apparently through the formation of a triple-stranded intermediate. The exact role of ATP hydrolysis is not clear, but it presumably drives the triplex intermediate towards products. Here we determine the position of bound ADP diffused into the recA crystal. We show that only the phosphates are bound in the same way as in other NTPases containing the G/AXXXXGKT/S motif. We propose that recA protein may change its conformation upon ATP hydrolysis in a manner analogous to one such protein, the p21 protein from the ras oncogene. A model is presented to account for the allosteric stimulation of DNA binding by ATP. The mechanism by which nucleoside triphosphate hydrolysis is coupled to the binding of another ligand in recA protein and p21 may be typical of the large class of NTPases containing this conserved motif.
RecA蛋白催化由ATP驱动的DNA分子同源配对和链交换。它是一种别构酶：ATP酶活性依赖于DNA，与ATP结合的RecA蛋白对DNA具有高亲和力，而与ADP结合的形式则具有低亲和力。在没有ATP水解的情况下，RecA蛋白仍然可以促进同源配对，显然是通过形成三链中间体来实现的。ATP水解的确切作用尚不清楚，但推测它会驱使三链中间体形成产物。在这里，我们确定了扩散到RecA晶体中的结合ADP的位置。我们发现只有磷酸基团的结合方式与其他含有G/AXXXXGKT/S基序的NTP酶相同。我们提出，RecA蛋白在ATP水解时可能会以类似于一种蛋白（来自ras癌基因的p21蛋白）的方式改变其构象。本文提出了一个模型来解释ATP对DNA结合的别构刺激作用。核苷三磷酸水解与RecA蛋白和p21中另一种配体结合相偶联的机制，可能是含有这种保守基序的一大类NTP酶的典型机制。
