InterPro domain: IPR028427

The oxidation of methionine residues in proteins is considered to be one of the consequences of oxidative damage to cells, which in many cases leads to the loss of biological activity. Peptide methionine sulphoxide reductase (Msr) reverses the inactivation of many proteins due to the oxidation of critical methionine residues by reducing methionine sulphoxide, (MetO), to methionine [ 1 ]. Methionine (Met) can be oxidised to the R and S diastereomers of methionine sulfoxide (MetO). Methionine sulfoxide reductases A (MsrA) and B (MsrB) reduce MetO back to Met in a stereospecific manner, acting on the S and R forms, respectively. Msr is present in most living organisms [ 2 , 3 ].

Many bacteria, particularly pathogens, possess methionine sulfoxide reductase MsrA and MsrB as a fusion form (MsrAB) [ 4 ]. This entry includes MsrB and the fusion form of these enzymes.

1. Thiol-disulfide exchange is involved in the catalytic mechanism of peptide methionine sulfoxide reductase. Proc. Natl. Acad. Sci. U.S.A. 97, 6463-8
2. Complete genome sequences of cellular life forms: glimpses of theoretical evolutionary genomics. Curr. Opin. Genet. Dev. 6, 757-62
3. A minimal gene set for cellular life derived by comparison of complete bacterial genomes. Proc. Natl. Acad. Sci. U.S.A. 93, 10268-73
4. Essential Role of the Linker Region in the Higher Catalytic Efficiency of a Bifunctional MsrA-MsrB Fusion Protein. Biochemistry 55, 5117-27