Selenoprotein

In molecular biology a selenoprotein is any protein that includes a selenocysteine (Se-Cys) amino acid residue. Among functionally characterized selenoproteins are five glutathione peroxidases (GPX) and three thioredoxin reductases, (TrxR/TXNRD) which both contain only one Se-Cys. Selenoprotein P is the most common selenoprotein found in the plasma. It is unusual because in humans it contains 10 Se-Cys residues, which are split into two domains, a longer N-terminal domain that contains 1 Se-Cys, and a shorter C-terminal domain that contains 9 Se-Cys. The longer N-terminal domain is likely an enzymatic domain, and the shorter C-terminal domain is likely a means of safely transporting the very reactive Selenium atom throughout the body.