Conservation and structural role of the mutated tyrosine (FV Y1702) in the A domains.

(Top) Alignment of a portion of the A domains of human FV, FVIII, and CP. The conserved tyrosine and proline residues are highlighted. The tyrosine residue affected by the FV 5279A/G mutation is boxed. (Bottom) Three-dimensional model of a portion of the A3 domain of FV based on the coordinates of CP. The highly conserved Y1702 residue forms 2 hydrogen bonds with Pro1618. The substitution of the tyrosine residue by a cysteine, predicted by the FV 5279A/G mutation, causes the loss of these interactions.