SEP15 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. Studies in mouse suggest that this selenoprotein may have redox function and may be involved in the quality control of protein folding. This gene is localized on chromosome 1p31, a genetic locus commonly mutated or deleted in human cancers. Recombinant human SEP15 (SC96C) protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.