Abstract: DNA-binding protein from starved cells(DPS)is a key protective proteins in bacterial growth under stress environment. DPS was expressed in prokaryotic cells and purified so as to study its self-assembly activity in vitro. The dps gene was amplified by polymerase chain reaction with specific primers that was inserted by his tag at 3' end and the template was genome from Escherichia coli strain 0111. After digested together with EcoR I and BamH I restrict enzymes, the dps and pBV220 were linked in order to construct pBVDPSHis expression vector. DPS expressed in E. coli by temperature induction was purified with affinity chromatography column and its self-assembly in vitro was tested with natural PAGE on the basis of protein molecular weight. DPS protection for DNA from oxidation was detected with 1.2% agarose electrophoresis. The results showed that a specific fragment with 522 bp length was acquired and pBVDPSHis vector was constructed correctly using enzyme digestion and sequencing tests. The DPS with 19.5 kD relative molecular weight on SDS-PAGE was identified with Western blotting, the purified DPS could self-assembly in vitro into polymers with much larger molecular weight than 19.5 kD in pH7.5 PBS solution and DPS protection DNA resistance to hydroxyl radicals oxidation could be demonstrated in Fenton reaction system. It was concluded that E.coli DPS expressed genetically in prokaryotic cells could correctly self-assembly to functional multi-polymers and had a ability of protection DNA from ROS oxidant damage in vitro.

Key words: Escherichia coli, DPS protein, prokaryotic expression, self-assembly, antioxidation