Assessing the role of RecA protein in the radioresistant bacterium, Deinococcus geothermalis

摘要

The moderately thermophilic bacteriumDeinococcus geothermalisexhibits 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 inD. geothermalis, the recA gene was isolated fromD. geothermalisand over expressed inEscherichia coli. After theD. geothermalisRecA protein (GeoRecA) was purified, the recombination activity was investigatedin vitro. GeoRecA efficiently promoted the strand exchange reaction between homologous linear double-stranded DNA and circular single-stranded DNA substrates at 50°C. LikeDeinococcus radioduransRecA protein (DraRecA), GeoRecA could promote DNA strand exchange reaction through normal and inverse pathways.Furthermore, GeoRecA complemented the RecA deficiency ofD. radiodurans. 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 RecAdeficiency ofE. coli, suggesting that GeoRecA require more strict intracellular conditions than DraRecA does tofulfill its function. This study provides new insights into the role of deinococcal RecA protein in radioresistance.