Hydrolysis of nucleoside triphosphates catalyzed by the recA protein of Escherichia coli. Characterization of ATP hydrolysis.

Both single- and double-stranded DNA stimulate the hydrolysis of ATP catalyzed by the recA protein of Escherichia coli. However, the reactions differ in their pH optima, response to recA protein concentration, salt sensitivity, and degree of inhibition by ADP, all of which reflect different requirements for the prehydrolytic binding of single- and double-stranded DNA by the RecA protein. Single- and double-stranded DNA stimulate hydrolysis of the same nucleoside triphosphates, principally (r,d)ATP and (r,d)UTP, suggesting that a single hydrolytic site is utilized in both single- and double-stranded DNA-dependent reactions. recA protein also catalyzes detectable ATP hydrolysis in the absence of exogenous DNA, although the rate is reduced 2 to 3 orders of magnitude. This DNA-independent hydrolysis shows the same nucleotide specificity at pH 6.2 and 7.5, although the rate of hydrolysis depends upon the pH.