Methionine-R-sulfoxide reductase B1 (MSRB1)

Methionine-R-sulfoxide reductase B1 (MSRB1) is a zinc-containing selenoenzyme encoded by the *SEPX1* gene in humans[4]. It is a key component of the cellular antioxidant defense system, with the primary function of reducing oxidized methionine residues (methionine-R-sulfoxide) back to methionine in proteins[1][2][3][4]. This activity repairs protein damage caused by oxidative stress and contributes to the maintenance of protein function and redox homeostasis. The catalytic mechanism involves the key selenocysteine residue at the active site, a resolving cysteine, and thioredoxin as a physiological electron donor[1][3]. Structural studies indicate a central β-sheet core stabilized by zinc and highly flexible N- and C-terminal regions[1][2]. MSRB1 has been implicated in aging, neurodegeneration, inflammation, and cancer, primarily through its role in repairing oxidative damage and supporting cellular integrity under stress. Currently, there are no known small-molecule drugs that directly target MSRB1, but it remains of interest in basic research on redox biology, protein repair, and oxidative stress-related diseases[1][2][3][4].

Other names

Methionine sulfoxide reductase B1SEPX1HSPC270MsrB1SelXSelRSepRSELENOXSELENORSelenoprotein XSelenoprotein R

Catalyzes the reduction of methionine-R-sulfoxide to methionine in proteins, using thioredoxin as an electron donor[3]