Apparent molecular weight of purified human factor VIII procoagulant protein compared with purified and plasma factor VIII procoagulant protein antigen.

We have compared apparent molecular weights of purified factor VIII procoagulant protein (VIII:C) and VIII:C antigen (VIII:CAg) by two different NaDodSO4 gel electrophoretic techniques. In a discontinuous NaDodSO4-7.5% polyacrylamide system, reduced and unreduced VIII:C, purified from commercial factor VIII concentrates by a monoclonal antibody immunoadsorption technique, showed a major doublet at mol wt 0.79 and 0.8 X 10(5) and less intense bands extending up to 1.9 X 10(5). In NaDodSO4-4% polyacrylamide/0.5% agarose gels (NaDodSO4-4% PAAGE), purified VIII:C had a major band of mol wt 1.0 X 10(5), with minor bands of mol wt 0.96, 1.1, 1.4, 1.6, 1.8, 2.2, and 2.4 X 10(5). In NaDodSO4-4% PAAGE of 125I-anti-VIII:C-Fab-VIII:CAg complexes, the major and minor forms of VIII:CAg in purified VIII:C had the same molecular weight as above when calculated by subtracting the molecular weight of 125I-Fab from 125I-Fab-VIII:CAg. In both plasma and factor VIII concentrate, a band of mol wt 2.4 X 10(5) predominated, and minor VIII:CAg forms of mol wt 2.6, 1.8, 1.2 and 1.0 X 10(5) were also visible. We conclude that the molecular weight of plasma VIII:CAg forms agree with those derived from protein stains of purified VIII:C in the NaDodSO4-4% PAAGE system, but that consistently lower molecular weight values are obtained for purified VIII:C in the discontinuous system. Both native and either disaggregated or proteolyzed VIII:C species are present in the purified VIII:C preparation.