Study On PprI Homologue DG0395in Deinococcus Geothermalis

Deinococcus radiodurans exhibits an extraordinary DNA repair capacity and it is an excellent model for DNA damage repair system.pprI serves as a general switch to regulate the expression of dozens of proteins from different pathsways after radiation, As shown in previous studies, PprI can regulate the expression of related genes including oxidative stress, energy metabolism, transcriptional regulation, signal transduction, protein folding and assembly in D. radiodurans. Based on these backgrounds, we studied a homolog of PprI protein from Deinococcus geothermalis. The results are as follows:1. The dg0395gene was cloned from D. geothermalis, constructed into expression plamid followed to transfer into Escherichia coli expression cells.2. Optimize the conditions of purifing DG0395protein and gain the pure protein through AKTA system.3.It was found that DG0395has metal protease activity in vitro as well as PprI protein, and the substrate is DdrO. Further its optimal tempreture is55℃, higher than that of PprI, who’s optimal tempreture is45℃. DG0395’s optimal PH is8.0. Both PprI and DG0395can been activated by Mn2+.4.pprl-deleted mutant strain YR1,pprI-complemented strain YR1-PprI and dg0395-complemented strain YR1-DG0395have been constructed. Compared to the wild strain R1, the deleted mutant strain YR1remarkably increased the cells’ sensitivity to various types of DNA damaging agents, such as ionizing radiation, ultraviolet irradiation, hydrogen peroxide, but pprI-complemented strain YR1-PprI and dg0395-complemented strain YR1-DG0395were almost as same as wild type R1. This results confirmed that DG0395is a significant DNA repair gene, which may has the same function of PprI.5. The growth rate of wild type R1, YR1, YR1-PprI and YR1-DG0395has been measured. We also has compared their growth at the defferent temperatures using plate point method. The results shows that either PprI or DG0395may play a great role in the growth of Deinococcus radiodurans, while pprI-complemented strain grows well at higher temperature as45℃.Studying the function of DG0395(a homolog of PprI in Deinococcus geothermalis) will be helpful for studying PprI. we found that DG0395has the metal protease activity and can complemented the function in pprI-deleted mutant strain YR1, which suggested that a common DNA repair pathway regulated by PprI exsist in Deinococcus.