Changes in cellular proteins of Deinococcus radiodurans following gamma-irradiation

In order to examine radiation-induced proteins in an extremely radioresistant bacterium, Deinococcus radiodurans R1, changes in cellular proteins after gamma-irradiation were analysed by two-dimensional gel electrophoresis and silver staining. Nine proteins (190, 120, 87,60, 58, 52, 46, 41 and 41 kDa) were increased (or appeared) and more than 13 proteins diminished after gamma-irradiation at 6 kGy. Increase of eight proteins (except for 190-kDa protein) was prevented when the cells were irradiated in the presence of chloramphenicol. Three proteins, 87, 60 and 46 kDa, continued to be synthesized during post-irradiation incubation, and the amounts of these proteins increased with higher doses in a range of 1-12 kGy. Changes in the amount of proteins after irradiation in the R1 strain were compared with those in a moderately radioresistant mutant (rec I) and in a highly radiosensitive mutant (rec30). These three proteins were increased in both R1 and recI, but not in rec 30, suggesting that they are characteristic for radioresistant strains. In addition, from the microsequence analysis, the 46-kDa protein was found to be homologous to the EF-Tu protein of Escherichia coli, whereas the remarkable homologous sequence to the N-terminal of the 60-kDa protein was not found among the known proteins.