Interaction of the RecA protein of Escherichia coli with single-stranded oligodeoxyribonucleotides

Piero R. Bianco and George M. Weinstock

The RecA protein of Escherichia coli performs a number of ATP-dependent, in vitro reactions and is a DNA-dependent ATPase. Small oligodeoxyribonucleotides were used as DNA cofactors in a kinetic analysis of the ATPase reaction. Polymers of deoxythymidilic acid as well as oligonucleotides of mixed base composition stimulated the RecA ATPase activity in a length-dependent fashion. Both the initial rate and the extent of the reaction were affected by chain length. Full activity was seen with chain lengths 30 nt. Partial activity was seen with chain lengths of 15–30 nt. The lower activity of shorter oligonucleotides was not simply due to a reduced affinity for DNA, since effects of chain length on Km ATP and the Hill coefficient for ATP hydrolysis were also observed. The results also suggested that single-stranded DNA secondary structure frequently affects the ATPase activity of RecA protein with oligodeoxyribonucleotides.