The studies outlined in this proposal will test the hypothesis that Factor VA and fibrinogen are released from the platelet, bind to specific sites on the membrane and become associated with cytoskeletal components either directly or through some transmembrane protein. Long term objectives will attempt to identify and characrerize both the cytoskeletal and membrane components that are involved in this postulated mechanism. Enzymatic assays and binding studies involving purified coagulation factors and platelets will be utilized as well as electron microscopic stuides in order to establish the proposed mechanism. Factor deficient platelets will be compared to normal platelets. The techniques of gel electrophoresis and column chromatography will be used to characterize the cytoskeletal factors and elements that are important in the proposed mechanism. The overall importance of this research proposal will be the elucidation of a potentially basis cellular mechanism, that in the long term may provide some insight into qualitative platelet disorders.