Fig. 3. Exposure of the ligand-binding site in the inactive bent conformation of full-length αIIbβ3.

The cryo-EM density map has been fitted with the bound γ-peptide from fibrinogen (as spheres) according to the X-ray structure of the headpiece (2VDR.pdb). The distance measured between the MIDAS metal ion (cyan sphere) and αIIb’s Arg⁹⁶² at the extracellular leaflet of the membrane (solid vertical line) is 71.5 Å. The calf1-calf2 leg domain axis (dashed line) is tilted from the normal by a 56° angle relative to the plane of the membrane (dotted line). The tilt angle is measured by a chord running from the metal ion at the αIIb genu (green sphere) to Ser⁹¹³ at the bottom of the calf2 domain (dotted line).