Assessing the role of RecA protein in the radioresistant bacterium

Sghaier, H.*; Sato, Katsuya; Oba, Hirofumi*; Narumi, Issei

The moderately thermophilic bacterium exhibits extraordinary resistance to ionizing radiation. RecA protein is considered to be one of the most important participants in radioresistance. To assess the role of the RecA protein in , the gene was isolated from and overexpressed in Escherichia coli. After the RecA protein (GeoRecA) was purified, the recombination activity was investigated . GeoRecA most efficiently promoted the strand exchange reaction between homologous linear double-stranded DNA and circular single-stranded DNA substrates at 50C. Like RecA protein (DraRecA), GeoRecA could promote DNA strand exchange reaction normal and inverse pathways. Furthermore, GeoRecA complemented the RecA deficiency of . These results indicate that GeoRecA is a functional homologue of DraRecA and plays an important role in radioresistance. However, unlike DraRecA, GeoRecA could not complement the RecA deficiency of , suggesting that GeoRecA require more strict intracellular conditions than DraRecA does to fulfill its function.