[Characterization of the changes in protease of Deinococcus radiodurans following irradiation]

The activity of protease from Deinococcus radiodurans R1 (DRR1) recovered from UV light and gamma-ray irradiation were characterized by SDS-PAGE zymography or FITC-labeled casein as substrate. It was demonstrated that proteases with large molecular weight were abundantly and constitutively expressed in DRR1, which consistent with the hypothesis that proteases were among the PHX (predicted highly expressed) proteins in DRR1. A broad range of gelatinolytic protease with molecular mass more than 140 kD and caseinolytic protease with molecular mass more than 120 kD were present in DRR1 cell. The prominent gelatinolytic protease of 174 kD was also active when denatured by SDS and displayed different operation dynamics during the repair process post UV-irradiation and gamma-irradiation, the protease showed its highest activity during gamma-irradiation and in the late recovery stage post-irradiation. Some proteases were demonstrated to be induced specifically by irradiation which suggests that these proteases may regulate breakdown of proteins responsible in sequential pathway, and an elaborate and fine tuning protease system may exist in D. radiodurans during the repair process post irradiation. The expression of protease was also influenced by the nutrition of the culture. A rod-shaped and radiation resistant bacterium RR533.2 isolated from soil in Beijing, China was revealed to display similar zymography pattern using gelatin or casein as substrate.