Protein recognition by cell surface receptors: physiological receptors versus virus interactions.

Protein-protein recognition is a major kind of receptor-ligand interaction: a living cell receives external signals to adapt to the environment through cell surface receptors. On opposing cell surfaces, such recognition bears distinct features: it is a multivalent, reversible and avidity-driven process. The affinity between each individual contacting pair is low. Viruses might take advantage of this low affinity to invade a host cell by evolving a stronger binding affinity to the surface receptors than that associated with physiological ligands. Structural data appear to support this notion.