Weinstock G M, McEntee K, Lehman I R
J Biol Chem. 1981 Aug 25;256(16):8845-9.
The DNA-dependent ATPase activity of the recA protein of Escherichia coli shows a complex dependence on ATP concentration. With a single-stranded (SS) DNA cofactor, the Hill coefficient for ATP is 3.3 at pH 8.1 and 1.4 at pH 6.2. With a double-stranded (DS) DNA cofactor, the Hill coefficient is 3.3 at pH 6.2 (no reaction is detectable at pH 8.1). In the presence of SS DNA, the Km for ATP is 20 microM, independent of pH, while with DS DNA at pH 6.2, KmATP is 100 microM. These and other observations indicate that the interaction of recA protein with ATP is influenced by both pH and DNA cofactor. ADP, UTP, dTTP, and GTP are competitive inhibitors of the ATPase activity of recA protein, indicating that there is a single binding site for nucleoside triphosphates. Nucleoside triphosphates, but not ADP, reduce the Hill coefficient for ATP hydrolysis and thus can contribute to the cooperative effect of ATP.
大肠杆菌RecA蛋白的依赖DNA的ATP酶活性对ATP浓度呈现出复杂的依赖性。在单链（SS）DNA辅因子存在的情况下，ATP的希尔系数在pH 8.1时为3.3，在pH 6.2时为1.4。在双链（DS）DNA辅因子存在的情况下，希尔系数在pH 6.2时为3.3（在pH 8.1时未检测到反应）。在存在SS DNA的情况下，ATP的Km为20 microM，与pH无关，而在pH 6.2时存在DS DNA的情况下，KmATP为100 microM。这些以及其他观察结果表明，RecA蛋白与ATP的相互作用受到pH和DNA辅因子的影响。ADP、UTP、dTTP和GTP是RecA蛋白ATP酶活性的竞争性抑制剂，表明存在一个核苷三磷酸的单一结合位点。核苷三磷酸而非ADP会降低ATP水解的希尔系数，因此可促进ATP的协同效应。
