Chromate resistance in Cupriavidus metallidurans CH34: molecular modeling from ChrC superoxide dismutase

Chromate has become an environmental pollutant present in different ecosystems due to its use in industry. Bacteria have evolved to resist stress produced by chromate. Among chromate-resistance mechanisms we can list Reactive Oxygen Species detoxification systems. CmeSOD (ChrC) protein from Cupriavidus metallidurans CH34 is a superoxide dismutase that mitigate oxidative stress caused by chromate. Cme-SOD protein belongs to Fe and Mn-dependent SOD family (pfam02777). The objective of this study was to analyze the threedimensional structure of the Cme-SOD protein, for which monomer and tetramer models of the enzyme were built. In the monomer model it was observed that Cme-SOD has a characteristic two-domain structure from iron-dependent SOD, additionally, Cme-SOD has an iron-binding site formed by conserved residues H26 and H75 in the Nterminal domain, and D157 and H161 in the domain Cterminal domain. It was show that chromate stress response SODs have a non-conserved residues in the active site (R37, N59, S71, D143 and Y164). These findings suggest the presence of a novel active site in this family of enzymes.