STUDIES ON FACTOR-VIII-RELATED PROTEIN .1. ULTRASTRUCTURAL AND ELECTROPHORETIC HETEROGENEITY OF HUMAN FACTOR-VIII-RELATED PROTEIN

Human factor VIII-related protein precipitates with specific heterologous antibodies directed against purified factor VIII and supports ristocetin-induced aggregation of washed platelets. We purified human factor VIII from cryoprecipitate by subsequent gel filtration on crosslinked large-pore agarose. Factor VIII-related protein appeared as a large aggregate following electrophoresis on 3% polyacrylamide gels in the presence of sodium dodecyl sulfate (SDS). The same material was separated into multiple bands (molecular weight in excess of several millions) following electrophoresis on SDS-1% agarose gels. After complete disulfide reduction of factor VIII-related protein and electrophoresis on SDS-5% polyacrylamide gels a single subunit chain (Mr ≈ 200 000) was revealed. Analysis of this protein, in its non-reduced state, by negative contrast electron microscopy showed filaments of markedly variable size. The calculated molecular weight of such filaments ranged from about 0.6 · 106 to 20 · 106. We conclude that size heterogeneity is an essential feature of human factor VIII-related protein. © 1979.