Factor Va-membrane interaction is mediated by two regions located on the light chain of the cofactor

Binding experiments on factor Va reveal that two phospholipid vesicle binding sites located inside factor Va's light chain introduce the fluorescent lipophilic probe 1-azidopyrene in the presence of vesicles containing either 100% phosphatedylcholine (PC) or 75% PC and 25% phosphatidylserine (PS). The light chain's Mr equal to 46000/48000 COOH-terminal portion contain Va's C1 and C2 regions. This region dominantly influences Va binding to vesicles containing 100% PS whereas electrostatic reactions influence reactions involving vesicles containing PC.