Efficient strand transfer by the RadA recombinase from the hyperthermophilic archaeon Desulfurococcus amylolyticus

The radA gene predicted to be responsible for homologous recombination in a hyperthermophilic archaeon, Desulfurococcus amylolyticus, was cloned, sequ enced, and overexpressed in Escherichia coli cells, The deduced amino acid sequence of the gene product, RadA, was more similar to the human Rad51 pro tein (65% homology) than to the E. coli RecA protein (35%), A highly purifi ed RadA protein was shown to exclusively catalyze single-stranded DNA-depen dent ATP hydrolysis, which monitored presynaptic recombinational complex fo rmation, at temperatures above 65 degrees C (catalytic rate constant of 1.2 to 2.5 min(-1) at 80 to 95 degrees C), The RadA protein alone efficiently promoted the strand exchange reaction at the range of temperatures from 80 to 90 degrees C, i.e., at temperatures approaching the melting point of DNA , It is noteworthy that both ATP hydrolysis and strand exchange are very ef ficient at temperatures optimal for host cell growth (90 to 92 degrees C).