Methionine Sulfoxide Reductase B (MSRB)

Oxidation of methionine residues in proteins is mediated by various biologic oxidants such as H(2)O(2), hydroxyl radicals, hypochlorite, and superoxide ions.

Methionine sulfoxide reductase B (MSRB), is a selenoprotein. The oxidation of methionine at the sulphur atom leads to alternative epimers: R form of Met(O) and S form of Met(O). MSRB can reduce R form of both free and protein incorporated methionine sulfoxide to methionine. It has a crucial role in protecting cells against oxidative damage. MSRA reduces only the S epimer of Met(O), and MSRB reduces the R epimer of Met(O) in proteins. Although the catalytic mechanisms of MSRA and MSRB are similar, the two MSRs have no sequence identity and no structural similarity.