Catalyzes the reduction of methionine sulfoxide (MetSO) to methionine in proteins. Involved in abiotic stress response. Plays a protective role against oxidative stress by restoring activity to proteins that have been inactivated by methionine oxidation. MSRB family specifically reduces the MetSO R-enantiomer. [thioredoxin]-disulfide + H2O + L-methionyl-[protein] = [thioredoxin]-dithiol + L-methionyl-(R)-S-oxide-[protein] Binds 1 zinc ion per subunit. Expressed in leaves and flowers. By salt, mannitol, cold, methyl viologen and abscisic acid (ABA). Lacks the conserved cysteine (here Thr-148) required for the reduction by thioredoxins (TRX) through a dithiol-disulfide exchange involving both redox-active Cys of TRX and MSRB. The reduction mechanism may occur through sulfenic acid formation on the catalytic cysteine (Cys-202). Belongs to the MsrB Met sulfoxide reductase family. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.