Sep15 and SelM are eukaryotic selenoproteins that have a thioredoxin-like domain and a surface accessible active site redox motif [1]. This suggests that they function as thiol-disulphide isomerases involved in disulphide bond formation in the endoplasmic reticulum [1]. Structurally it resembles the thioredoxin-fold.

1: NMR structures of the selenoproteins Sep15 and SelM reveal redox activity of a new thioredoxin-like family. Ferguson AD, Labunskyy VM, Fomenko DE, Arac D, Chelliah Y, Amezcua CA, Rizo J, Gladyshev VN, Deisenhofer J; J Biol Chem. 2006;281:3536-3543. PMID:16319061