May be involved in redox reactions associated with the formation of disulfide bonds (By similarity). May contribute to the quality control of protein folding in the endoplasmic reticulum (PubMed:24415556). May regulate protein folding by enhancing the catalytic activity of UGGT1/UGCGL1 and UGGT2/UGCGL2 (PubMed:24415556). Forms a tight complex with UGGT1/UGCGL1 (PubMed:24415556). Interacts with UGGT2/UGCGL2 (PubMed:24415556). Interacts with RDH11 (PubMed:29410696). The association with UGGT1/UGCGL1 is essential for its retention in the endoplasmic reticulum. Higher levels in prostate and thyroid gland. The N-terminus is blocked. Belongs to the selenoprotein M/F family. It is uncertain whether Met-1 or Met-4 is the initiator. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.