FIG 7.

Summary of the receptor recognition mechanisms of coronaviruses in a three-dimensional view. The overall structure of trimeric SARS-CoV spike complexed with ACE2 is shown; it includes both the schematic topology of the spike and the negative-stain electron micropic images of the spike ectodomain (upper right). TM, transmembrane anchor. IC, intracellular tail. The structures and functions of coronavirus S1 domains are listed. The question marks indicate possible tertiary structures of coronavirus S1 domains.