Figure 2 |. The αvβ8 headpiece rotates about a flexible αv-knee to survey the environment.

a to c, A single dataset of integrin αvβ8–8B8–68 complex is used to generate six independently-refined integrin structural subclasses (labeled i to vi). These structures are aligned to each other based on the calf regions of the αv-lower leg. Each vertical panel shows three views of each subclass in solid color and the other five at 40% transparency. These six conformational snapshots represent the range of continuous motion of the αvβ8 headpiece. The overall motion of the headpiece is qualitatively similar to the path of a sunflower following the sun, presumably to expand the sampling area. Models (i) and (vi) represent the most extreme conformations measured as the angle of the hybrid domain with the αv-lower leg. d and e, Close-up front and side views of the αv-knee and point of contact between the Psi-EGF1 and the αv-leg shown as the atomic models in ribbon diagram fitted to the density map of subclass (i) (d) and (vi) (e). Arrows indicate the αv-knee region. The color code is: αv-green; β8-blue; Fab 68-orange; Fab 8B8-yellow.