The PROC gene, located on chromosome 2q14.3, encodes a vitamin K-dependent plasma glycoprotein. This protein is an essential plasma anticoagulant produced from the liver; it remains inactive until it cleaves to its activated form by the thrombin-thrombomodulin complex. The activated protein regulates blood coagulation by inactivating factors Va and VIIIa in the presence of calcium ions and phospholipids. Defects in this protein are the cause of protein C deficiency, an important risk factor of hereditary thrombophilia.