EXPRESSION OF GLUTATHIONE PEROXIDASE-I GENE IN SELENIUM-DEFICIENT RATS

We have characterized a cDNA pGPX1211 encoding rat glutahione peroxidase I. The selenocyteine in the protein corresponded to a TGA codon in the coding region of the cDNA, similar to earlier findings in mouse and human genes, and a gene encoding the formate dehydrogenase from Escherichia coli, another selenoenzyme. The rat GSH peroxidase I has a calculated subunit molecular weight of 22,155 daltons and share 95% and 86% sequence homology with the mouse and human subunits, respectively. The 3''-noncoding sequence (> 930 bp) in pGPX1211 is much longer than that of human sequences. We found that glutathione peroxidase I mRNA, but not the polypeptide, was expressed under nutritional stress of selenium deficiency where no glutathione peroxidase I activity can be detected. The failure of detecting any apoprotein for the glutathione peroxidase I under selenium deficiency and results published from other laboratories supports the proposal that selenium may be incorporated into the glutahione peroxidase I co-translationally.