Sequence of a cDNA coding for human glutathione peroxidase confirms TGA encodes active site selenocysteine

The authors have isolated a cdNA coding the human enzyme from a kidney library in lambda gt10 by cross-hybridization with a bovine cDNA; 24 of 5300 clones hybridized with the probe. The active site selenocysteine residue (-CH sub(2) SeH) at position 47 (i.e. SeC) is encoded by the nonsense codon, TGA, as is similarly observed in the mouse gene. Interestingly evidence suggests that the selenium atom is incorporated cotranslationally rather than via a posttranslational modification step. This clone possesses 5 bp of the 5'-untranslated region, the 603 bp coding region, 223 bp to the 3'-untranslated region and a canonical polyadenylation signal, AATAAA, upstream of the polyA tract. The amino acid sequence reveals the protein possesses approximately 87% and 85% homology with preprocessed bovine and mouse enzymes, respectively.