Computational analysis of Asp519 and Glu665 mutations of coagulation factor FVIIIa: Implications for enhanced binding affinity of A2-domain.

The A2-domain of blood coagulation factor VIIIa is non-covalently bound to the A1 and A3 domains via weak intermolecular interactions. Functional instability due to rapid dissociation of A2-domain from the active FVIII in blood presents a major hurdle for the therapeutic applications of FVIIIa to treat Hemophilia-A. To identify the ideal hot-spot residues at the interface of A2 and A1/A3 domains that could enhance the structural stability of FVIIIa, we performed a comprehensive computational mutagenesis study of two A2-domain residues, Asp519 and Glu665, that interface the A1 and A3-domains. Each residue was mutated to 15 uncharged amino-acids and the mutant structures were refined by MD simulations. Based on the estimated relative binding affinities of mutant structures, we predict that the mutation of Asp519 to Leu, Gln, Thr, Val and the mutation of Glu665 to Val, Ile, Met, Asn and Trp enhance the A2-domain binding affinity by more than 20kcal/mol, compared to the WT structure. We anticipate that these predictions will be valuable for enzymatic studies towards the rational design of FVIIIa synthetic constructs with improved A2-domain binding affinity.