Tags: Protein.
Protein S is a vitamin K-dependent plasma glycoprotein synthesized in the endothelium. In the circulation Protein S exists in two forms: a free form and a complex form bound to complement protein C4b-binding protein (C4BP). In humans protein S is encoded by the PROS1 gene. In 1979 researchers in Seattle Washington first discovered protein S and arbitrarily named it after the city of its discovery.