| Abstract: | Incubation of the recA protein of Escherichia coli with the ATP analog adenosine 5'-O-(3-thiotriphosphate) (ATP(gamma S)) in the presence of DNA produces an irreversible inhibition of ATPase activity, although in the presence of ATP, ATP(gamma S) shows an initial competitive inhibition. ATP(gamma S) is not appreciably hydrolyzed by recA protein and the inhibition of ATPase activity is due to the formation of stable complexes which contain equimolar amounts of ATP(gamma S) and recA protein. Formation of stable complexes requires DNA, which is also stably bound to recA protein in the presence of ATP(gammaS), at a ratio of 5 to 10 nucleotides/recA protein monomer. The DNA requirement is satisfied by either single-or double-stranded DNA, and in the latter case, the pH dependence is comparable to that observed for ATP hydrolysis. Binding of ATP(gamma S) is inhibited by other nucleoside di- and triphosphates with efficiencies corresponding to their inhibitory effects on the ATPase activity of recA protein. |
