Location of the P¹⁴⁵ in the β-propeller model of the amino-terminus of an IIb -chain subunit.

This figure was adapted from that of Springer13 and shows views of the αIIb amino-terminus looking down from the top (A) and laterally (B). In the model, P¹⁴⁵, indicated as the blue circle numbered 1, is located at the transition between the W2 loop and the W2 blade. A disulfide bond between C¹⁴⁶ and C¹⁶⁹ is shown in red. Seven other mutations that affect ligand binding to αIIb are shown as purple (#2-7) and pink (#8) circles. The naturally occurring mutation αIIb^L183P (#2) produces a phenotype similar to αIIb^P145A.6The αIIb^L183P and 5 of the other mutations (G¹⁸⁴A [#3], Y¹⁸⁹A [#4], Y¹⁹⁰A [#5], F¹⁹¹A [#6], and G¹⁹³A [#7]) are present in the second surface loop of W311 and the seventh mutation (D²²⁴V [#8]) is found on the next loop at the interface between W3 and W4.12 As best appreciated from the lateral view shown in (B), these mutations lie on the upper and outer side of the β-propeller. The location of mutations that completely prevent αIIbβ3 expression on the platelet surface14,26,44,45 are indicated as green squares in the left side of the figure, and can be seen to lie at the bottom and/or opposite side of the propeller.