Interactions of vitamin K dependent proteins with calcium ions and phospholipid membranes

G. L. Nelsestuen

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41 Scopus citations


The calcium-dependent interaction of vitamin K-dependent proteins with membranes is a complex process that minimally consists of 1) calcium binding to the protein and an essential calcium-dependent protein transition, 2) an essential calcium-membrane interaction, and 3) formation of the protein-membrane complex. Below about 5 mM calcium, the protein-membrane complex binds more calcium than the sum of the components but at higher concentrations protein-membrane binding is not accompanied by additional cation binding. These protein-membrane interactions function in blood coagulation by increasing the binding affinity of the active site. The increased affinity results from the additive effects of protein-membrane (e.g., prothrombin-, factor Xa- factor V-membrane) interactons and protein-protein (e.g., factor Xa-factor V and prothrombin-factor V) interactions. The prothrombinase complex can be viewed kinetically as a dissociable three-component enzyme (factor Xa, factor V, and phospholipid) acting on the soluble susbtrate, prothrombin.

Original languageEnglish (US)
Pages (from-to)2621-2625
Number of pages5
JournalFederation Proceedings
Issue number12
StatePublished - Dec 1 1978


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