Abstract
In platelets, coagulation cofactor V is stored in complex with multimerin 1 in alpha-granules for activation-induced release during clot formation. The molecular nature of multimerin 1 factor V binding has not been determined, although multimerin 1 is known to interact with the factor V light chain. We investigated the region in factor V important for multimerin 1 binding using modified enzyme-linked immunoassays and recombinant factor V constructs. Factor V constructs lacking the C2 region or entire light chain had impaired and absent multimerin 1 binding, respectively, whereas the B domain deleted construct had modestly reduced binding. Analyses of point mutated constructs indicated that the multimerin 1 binding site in the C2 domain of factor V partially overlaps the phosphatidylserine binding site and that the factor V B domain enhances multimerin 1 binding. Multimerin 1 did not inhibit factor V phosphatidylserine binding, and it bound to phosphatidylserine independently of factor V. There was a reduction in factor V in complex with multimerin 1 after activation, and thrombin cleavage significantly reduced factor V binding to multimerin 1. In molar excess, multimerin 1 minimally reduced factor V procoagulant activity in prothrombinase assays and only if it was added before factor V activation. The dissociation of factor V-multimerin 1 complexes following factor V activation suggests a role for multimerin 1 in delivering and localizing factor V onto platelets prior to prothrombinase assembly.
Highlights
Activated coagulation factor V is a key non-enzymatic cofactor that is an essential component of the prothrombinase com
We report that the factor V light chain and its C2 region are important for multimerin 1 (MMRN1) binding and that the binding of factor V to MMRN1 is
We report that activation of factor V by thrombin alters the binding of factor V to MMRN1, analogous to the way activation of factor VIII alters its binding to von Willebrand factor (VWF) [13]
Summary
Activated coagulation factor V is a key non-enzymatic cofactor that is an essential component of the prothrombinase com-. The intent of our present study was to identify the region of factor V important for MMRN1 binding and its possible overlap with the factor Va phospholipid binding site in the C2 domain.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have