Plays a role as a glutathione (GSH)-dependent antioxidant. May be involved in a redox-related process. May play a role in the myopathies of selenium deficiency (By similarity). Interacts with DPYSL2, PRDX1, YWHAB, YWHAG, HSP70 and HSP90. Highest levels detected in skeletal muscle, tongue, heart and brain. Expressed at significantly higher levels in female skeletal muscle than in male and at slightly higher levels in female cardiac muscle than in male (at protein level). Also detected at low levels in liver. With bound glutathione. Major form in muscle. With an undetermined modification. Without bound glutathione or undetermined modification. Belongs to the SelWTH family. Selenoprotein W subfamily.