Summary
Three dimensional homology models for the C1 and C2 domains of factor VIII (FVIII)
were generated. Each C domain formed a β-sandwich, and C1 was covalently connected
to C2 in a head-to-head orientation. Of the >250 missense mutations that cause FVIII
deficiency and hemophilia A, 34 are in the C domains. We used the FVIII C1-C2 model
to infer the structural basis for the pathologic effects of these mutations. The mutated
residues were divided into four categories: 15 conserved buried residues that affect
normal packing of the hydrophobic side chains, 2 non-conserved buried residues that
affect structure, 11 conserved exposed residues and 6 non-conserved exposed residues.
The effects of all 34 missense mutations can be rationalized by predictable disruptions
of FVIII structure while at most four mutations (S2069F, T2154I, R2209Q/G/L and E2181D)
may affect residues directly involved in intermolecular interactions of FVIII/VIIIa
with other coagulation factors or vWF.
Key words
Hemophilia A - Factor VIII - homology modeling - von Willebrand factor - coagulation