Fig. 7. PVR and IC1-binding modes and footprints. (A) View of the electron density for a PV-bound PVR molecule (blue lines), the PV1/M molecular surface (yellow) and an HRV16-bound IC1 molecule (red). A ribbon representation of the crystal structure of domains 1 (D1) and 2 (D2) of IC1 (Bella et al., 1998; Casasnovas et al., 1998b) fitted in the cryo-EM electron density of the reported HRV16–IC1 complex (Olson et al., 1993) is shown. The IC1 molecule has similar orientation to that previously reported (Bella et al., 1998). Structures of PV1/M and HRV16 were superimposed to generate the figure. (B) Lines defining the footprint of PVR (white) and IC1 (red) were drawn around the virus proximal cryo-EM density of the bound receptor molecules. The panel shows a view toward the center of the particle, with two PV1/M promoters colored in yellow and green. Defined receptor-binding residues in PV1 (see Figure 6) and HRV (Colonno et al., 1988) are colored magenta and cyan, respectively.