Discrimination between iron and manganese superoxide dismutases from amino acid sequence data

Abstract

It is well known that the iron and manganese superoxide dismutases (Fe and Mn SODs) are structurally homologous. The protein fold and the active site structure are similar in the two classes of SOD. The metal ion ligands are the same. Except for some Fe/Mn SODs, termed cambialistic, Fe and Mn SODs have absolute metal ion specificity for expression of catalytic activity. Furthermore, Fe SODs in contrast to Mn SODs are inactivated by hydrogen peroxide. Subtle structural properties are thought to be responsible for the distinguishing features of the Fe and Mn SODs. The Parker and Blake signature or the residues at positions 78, 79, 86, 151 and 152 (T. thermophilus Mn SOD sequence numbering) defined by Parker and Blake [1] as A-Q-Y-A-G for Fe SODs and G-G-F-Q-D for Mn SODs is a useful guideline for distinguishing between Fe and Mn SODs. The present work is an attempt to utilize more primary structure information for this purpose. It is based on the concept of a consensus sequence for each class of SOD that is contained in the work of Van Camp et al.