Nuclear monooxygenase that promotes depolymerization of F-actin by mediating oxidation of specific methionine residues on actin and regulates the srf signaling. Acts by modifying nuclear actin subunits through the addition of oxygen to form methionine-sulfoxide, leading to promote actin filament severing and prevent repolymerization (By similarity). Acts as a key regulator of the srf signaling pathway elicited by nerve growth factor and serum: mediates oxidation and subsequent depolymerization of nuclear actin, leading to increase mkl1/mrtf-a presence in the nucleus and promote srf:mkl1/mrtf-a-dependent gene transcription (By similarity). H(+) + L-methionyl-[F-actin] + NADPH + O2 = H2O + L-methionyl-(R)-S-oxide-[F-actin] + NADP(+) Belongs to the Mical family.