Amino acid sequence around the active-site selenocysteine of rat liver glutathione peroxidase.

Glutathione peroxidase (glutathione:hydrogen-peroxide oxidoreductase, EC 1.11.1.9) from rat liver was purified to at least 95% purity. A peptide of 16 amino acids, including the active-site selenocysteine (SeCys) residue, was isolated from a tryptic digest by reverse-phase HPLC and gel filtration. The amino acid sequence of the first 46 residues of glutathione peroxidase was obtained from the overlapping sequences of the tryptic selenopeptide and the intact subunit. The selenocysteine residue was located at residue 41, and the sequence of the tryptic selenopeptide was Val-Leu-Leu-Ile-Glu-Asn-Val-Ala-Ser-Leu-SeCys-Gly-Thr-Thr-Thr-Arg. The sequence was analyzed by computer for homology with other proteins, but no closely related sequences were found. Glutathione peroxidase is the first selenoprotein for which sequence data have been obtained, and the methods described should be applicable to mapping and to sequence analysis of Se-containing peptides from other selenoproteins.