Binding of blood coagulation factor VIII and its light chain to phosphatidylserine/phosphatidylcholine bilayers as measured by ellipsometry.

作者: J Spaargaren , P L A Giesen , M P Janssen , J Voorberg , G M Willems

DOI: 10.1042/BJ3100539

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摘要: Factor VIII is a plasma protein which plays an essential role in the coagulation system. When assembled with enzyme IXa on phospholipid membrane, it functions as cofactor complex that cleaves zymogen X to Xa. We studied binding of both and light chain planar bilayers consisting 25% dioleoylphosphatidylserine 75% dioleoylphosphatidylcholine (PSPC) by ellipsometry. Equilibrium-binding studies revealed its bind high affinity PSPC bilayers. The VIII, dissociation constant Kd 0.24 nM, was comparable (Kd 0.49 nM). Maximal 2.3 mmol per mol for 7.1 chain. Adsorption kinetics conformed classical Langmuir adsorption model yielding constants calculated from rates were similar those obtained equilibrium-binding studies. In contrast, measurements desorption deviation expected single class sites. rate increased increasing residence time lipid membrane. This indicates transition configuration lower affinity. As this time-dependent change could affect validity measurement parameters, particular determinations carried out long timescale, also estimated at half-maximal surface coverage, relatively rapid procedure determination A 0.087 nM under these conditions. Measurement equilibrium small vesicles, system rapidly attained, resulted parameters = 0.13 maximal 2.8 PSPC). These data confirm results Taken together, our indicate means 80 kDa chain, binds below concentration therefore may readily exposed membranes physiological

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