Structures of RV-A and RV-C colored by radial distance (Å) to the virus center. A black triangle indicates one icosahedral asymmetrical unit on each of the two viruses. A, Structure of RV-A with an enlarged triangle to show outline of the canyon, receptor pocket (dotted oval), receptor footprint (dotted circle, shaded gray), and pore (dark circle). B, Structure of RV-C with an enlarged triangle to show outline of binding pocket (dotted oval) and region of finger-like projection (dotted square, shaded red). A continuous canyon is absent in RV-C. RV = rhinovirus.