Characterization of Cu- and Zn-containing superoxide dismutase of<i>Rhodobacter sphaeroides</i>

Abstract

Rhodobacter sphaeroides has a cuprozinc-containing superoxide dismutase (CuZnSOD) in its periplasm in addition to the cytoplasmic SOD that appears to contain iron (FeSOD). The FeSOD is constitutively expressed under the growth conditions examined, whereas the CuZnSOD is detected only when the light-harvesting complexes are found. The CuZnSOD expression is regulated post-transcriptionally, and the enzyme appears to protect the photoheterotrophic cells from periplasmic superoxide that may be generated by exposure of the cells to low O2 under the illuminated conditions at 10 W/m2.