Summary
The C-terminal C domains of activated coagulation factor VIII (FVIIIa) are essential
to membrane binding of this crucial coagulation cofactor protein. To provide an overall
membrane binding mechanism for FVIII, we performed simulations of membrane binding
through coarsegrained molecular dynamics simulations of the C1 and C2 domain, and
the combined C-domains (C1+C2). We found that the C1 and C2 domain have different
membrane binding properties. The C1 domain uses hydrophobic spikes 3 and 4, of its
total of four spikes, as major loops to bind the membrane, whereas all four of its
hydrophobic loops of the C2 domain appear essential for membrane binding. Interestingly,
in the C1+C2 system, we observed cooperative binding of the C1 and C2 domains such
that all four C2 domain spikes bound first, after which all four loops of the C1 domain
inserted into the membrane, while the net binding energy was higher than that of the
sum of the isolated C domains. Several residues, mutations of which are known to cause
haemophilia A, were identified as key residues for membrane binding. In addition to
these known residues, we identified residues from the C1 and C2 domains, which are
involved in the membrane binding process, that have not been reported before as a
cause for haemophilia A, but which contribute to overall membrane binding and which
are likely candidates for novel causative missense mutations in haemophilia A.
Keywords
Coarse-Grained Molecular Dynamics (CGMD) - Coagulation FVIII - C domains - membrane
- haemophilia A