cDNA and deduced polypeptide sequence of a mouse selenoprotein P.

An 11-day embryonic Swiss Webster/NIH mouse cDNA library was screened with a partial murine selenoprotein P cDNA probe and a murine selenoprotein-P-type cDNA clone of 2075 bp length was obtained. The clone contained a 5'-leader sequence of 132 bp length, the selenoprotein P coding frame, and 803 base pairs in the 3' untranslated region. Alignment and RNA folding studies revealed the presence of two well conserved selenocysteine inserting motifs in the 3' flanking region. The deduced polypeptide sequence comprises 380 residues including ten selenocysteines. Identical amino acid residues in homologous positions are 86%, 71%, and 64% when compared to the previously reported selenoprotein P sequences of rat, man, and cattle, respectively. The comparatively low similarity between the selenoprotein P sequences reported so far leaves open the question whether they belong to the same molecular clade.