A Single Mutation is Sufficient to Modify the Metal Selectivity and Specificity of a Eukaryotic Manganese Superoxide Dismutase to Encompass Iron

Abstract

We have generated a site‐directed mutant of the manganese superoxide dismutase SOD‐3 of C.elegans (MnSOD‐3) which modifies the metal specificity of the enzyme. While wild‐type MnSOD‐3 functions with manganese in the active site (3600 U mg−1 of protein) it has little or no activity when iron is incorporated. However, when histidine replaces glutamine 142 in the active site, the enzyme retains 50 % of its activity and becomes cambialistic for its metal cofactor exhibiting very similar specific activity with either manganese or iron