SEPW1 is a selenoprotein, which contains a selenocysteine (Sec) residue at its active site. The selenocysteine is encoded by the UGA codon that normally signals translation termination. The 3' UTR of selenoprotein genes have a common stem-loop structure, the sec insertion sequence (SECIS), that is necessary for the recognition of UGA as a Sec codon rather than as a stop signal. This protein shows highest expression in skeletal muscle and heart, and may be involved in oxidation-reduction reactions. A retroprocessed pseudogene, SEPW1P, has been identified and mapped to chromosome 1p35-34. Recombinant human SEPW1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.