Dependence on Vitamin K-dependent Protein S for Eukaryotic Cell Secretion of the beta-Chain of C4b-binding Protein
The anticoagulant vitamin K-dependent protein S (PS) circulates in plasma in two forms, 30% free and 70% being bound to the complement regulatory protein C4b-binding protein (C4BP). The major C4BP isoform consists of 7 alpha-chains and 1 beta-chain (C4BP beta(+)), the chains being linked by disulfide bridges. PS binds to the beta-chain with high affinity. In plasma, PS is in molar excess over C4BP
