Characterization of iron superoxide dismutase cDNA from Dunaliella salina

Abstract

Photosynthetic organisms, such as unicellular green algae have photo-protective mechanisms that are critical for survival under conditions of excess photon absorption. The absorbed light energy which is more than needed can excitate electrons of photosystem and generate reactive oxygen species (ROS). Living organisms evolved antioxidant defense mechanisms to remove excess O2- and H2O2. Superoxide dismutase (SOD) is a metaloenzyme which catalyzes conversion of O2-(superoxide anion) to H2O2 and O2. Generally, localization of Fe-SOD is in the chloroplast and this protein plays a photo-protective role. In this work we isolated cDNA encoding Fe-SOD from Dunaliella salina. The cDNA sequence showed highest similarity with Fe-SOD gene of Chlamydomonas(89% identities). Northern blot analysis revealed that Fe-SOD expression is induced by light stress. Also antioxidant effect of E. coli expressed Fe-SOD protein of D. salina was detected by using a non-denaturing PAGE analysis.