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Comparative Protein Modeling of Superoxide Dismutase Isoforms in Maize

Kaliyugam Shiriga, Rinku Sharma, Krishan Kumar, Firoz Hossain and NepoleanThirunavukkarasu

Superoxide dismutase (SOD) is one of the major classes of antioxidant enzymes, which protects the cellular and subcellular components against harmful reactive oxygen species. In maize, three types of SODs are present based on their constituent metal ions, namely Cu /Zn-SOD, Mn-SOD and Fe-SOD. In this study we critically assess the phylogenetic relationship and structural models for maize Cu/Zn SOD, Mn SOD and Fe SOD. The phylogenetic analysis showed that Mn-SOD and Fe-SODs in maize have a greater degree of similarity between them as compared to Cu/Zn-SODs. The secondary structure of Mn-SOD and Fe-SODs demonstrated similar characteristics of helices, sheets, turns and coils revealed that Mn-SOD and Fe-SOD were closely related, whereas Cu/Zn-SOD evolved independently. We found Mn-SOD and Fe-SOD had structurally analogous beta sheets. Homology modeling-enabled three-dimensional structure prediction helped to understand the molecular functions of SOD proteins in improving tolerance to oxidative stress in maize.