Figure 2.

Structure of CR4, integrin α_Xβ₂. (A) Cartoon of α_Xβ₂ molecule 1 in lattice A and (B) an extended model made by adjusting domain interfaces at and near the knees. Disulfides are gold sticks, and glycans are sticks with white carbons. Ca and Mg ions are gold and green spheres, respectively. Smaller spheres show Cα atoms of conformation-associated epitopes and C-terminal residues. (C–F) Representative α_Xβ₂ EM class averages. The presence (+) or absence (−) of a disulfide after the α_X and β₂ C-termini (CC) and subsequent linker and coiled-coil (coil) is indicated. (G) Cartoon of α_IIbβ₃ (Zhu et al, 2008) in same orientation and style as α_Xβ₂ in (A). (H) Differences in interdomain angles between 10 molecules of α_Xβ₂ and 2 molecules of α_IIbβ₃ (left panel), or among 10 molecules of α_Xβ₂ (right panel). The mean values of interdomain angles are shown as bars and the maximal and minimal angles are shown in dashed or dotted lines, respectively.