Effect of αIIb mutations on electrostatic potential.

The electrostatic potential was calculated at each of the 4 calcium positions in the αIIb β-propeller model. The Glanzmann thrombasthenia mutations Val298Phe and Ile374Thr, and the experimental mutations Val298Ala, Val298Leu, Ile374Leu, and Ile374Val were then inserted into the model and the electrostatic potentials were calculated. The relative change in electrostatic potential resulting from each mutation is depicted for each calcium position as a positive or negative bar. The normal electrostatic potential at each calcium position is arbitrarily set to 0. A positive change in electrostatic potential of more than 2 (the charge of calcium) would be expected to decrease the ability of calcium to bind, whereas a negative change in electrostatic potential would increase the ability of calcium to bind.