Enables peptide-methionine (S)-S-oxide reductase activity. Predicted to be involved in aging and cellular response to oxidative stress. Located in mitochondrion. Is expressed in several structures, including musculoskeletal system; nervous system; respiratory system; sensory organ; and testis. Orthologous to human MSRA (methionine sulfoxide reductase A). [provided by Alliance of Genome Resources, Apr 2022]