CHARACTERIZATION OF A RECA RAD51 HOMOLOG FROM THE HYPERTHERMOPHILIC ARCHAEON PYROCOCCUS SP KOD1/

The Pk-rec gene, encoding a RecA/RAD51 homologue from the hyperthermop hilic archaeon Pyrococcus sp. KOD1, was expressed in Escherichia coli, The recombinant Pk-REC was purified to homogeneity and was shown to b e in a dimeric form. A striking property of the purified recombinant P k-REC was the unusual DNase activity on both single- and double-strand ed DNAs along with the ATPase activity, The reaction product of this D Nase activity was mononucleotides, The optimum temperature and pH for the DNase activity were 60 degrees C and 8-8.5, respectively. In addit ion, the metal ion requirement for DNase activity was different from t hat for the ATPase activity. The protein exhibited no DNase activity i n the presence of Zn2+ ion, which was one of the most preferable dival ent cations for ATPase activity. Another unique characteristic of the recombinant protein was that the reaction product of ATPase activity w as AMP instead of ADP. Pk-REC may represent a common prototype of the RecA family proteins with high RecA-like activity.