Expression and Characterization of an Active Chimeric Protein of Human Extracellular Superoxide Dismutase and hCuZnSOD in Pichia pastoris

Mammalian cells express two isoforms of Cu- and Zn-containing superoxide dismutases(SODs), CuZn-SOD and extracellular SOD(EC-SOD), involved in the defense system against reactive oxygen species(ROS). The two SODs have structurally homologous centre domain with distinct N- and C-terminuses, resulting in the different characteristics of the structure and function of the two molecules. We generated a hybrid SOD molecule(namely hySOD) via replacing the N- and C-terminuses of hCuZnSOD with the counterparts of hEC-SOD. The hySOD was expressed in host Pichia pastoris and the purified protein was a dimer with a molecular weight of about 34000. A series of activity analyses indicates that the hySOD is similar to hEC-SOD in heat-stability, and has the activity of protecting the host cell against heat shock and oxidative stress. Our results show evidence for the study on the compound activity of multiple SOD molecules, and may be important for understanding the relationship between structure and function of hEC-SOD and hCuZnSOD.