title: Binding of human blood-coagulation Factors IXa and X to phospholipid membranes.
abstract: A simple centrifugation technique has been developed to study the interaction of human coagulation Factors IXa and X with phospholipid membranes. In the presence of Ca2+, equimolar phosphatidylserine/phosphatidylcholine membranes form tight complexes with Factor X (KD = 2.8 X 10(-8) M); the KD is independent of the phospholipid concentration. Binding sites are available for about 2 mmol of Factor X/mol of phospholipid. Factor IXa has a slightly higher affinity for the phospholipid membrane (KD = 1.2 X 10(-8)M), and competes with Factor X for binding. The experimentally observed competition between Factor X and Factor IXa is in agreement with a model that describes the binding of two distinct ligands to a single class of independent binding sites.
mesh_terms: D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005164:Factor IX / Q000378:metabolism*; D015949:Factor IXa; D005170:Factor X / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008563:Membrane Lipids / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D008563:Membrane Lipids; D010743:Phospholipids; D005164:Factor IX; D005170:Factor X; D015949:Factor IXa; D002118:Calcium