Methionine-R-sulfoxide reductase; reduces the R enantiomer of free Met-SO, in contrast to Mxr2p which reduces Met-R-SO in a peptide linkage; has a role in protection against oxidative stress; binds and degrades patulin, a polyketide mycotoxin, forming E-ascladiol; strong substrate specificity towards patulin but not other mycotoxins; relative distribution to the nucleus increases upon DNA replication stress