Mammalian selenium-containing proteins

Mammalian selenium-containing proteins can be divided into three groups: pr oteins containing nonspecifically incorporated selenium, specific selenium- binding proteins, and specific selenocysteine-containing selenoproteins. Se lenoproteins with known functions identified so far include five glutathion e peroxidases, two deiodinases, several thioredoxin reductases, and selenop hosphate synthetase 2. Alternative splicing leads to a greater variety of s elenoproteins, as was shown in the cases of a specific sperm nuclei glutath ione peroxidase and some thioredoxin reductases. Selenoprotein P, selenopro tein W, a 15-kDa selenoprotein, an 18-kDa selenoprotein, and several seleno proteins identified in silico from nucleotide sequence databases were found to contain selenocysteine but their functions are not known. Gel electroph oretic separation of tissue samples from rats labeled in vivo with Se-75 sh owed the existence of further selenium-containing proteins.