The three faces of paramyxovirus attachment proteins.

Enveloped viruses encode membrane-associated glycoproteins that direct the initial stages of virus infection. These usually oligomeric structures bind virions to cell surface receptors and, subsequently, direct fusion of viral membranes with cellular membranes. These structures are also the primary targets of neutralizing antibody as well as potential targets for antiviral agents. In several systems, solving the structure of a virus surface glycoprotein has been enormously valuable to our understanding of virus entry and the mechanisms of entry inhibition. The recent report of the structure of a paramyxovirus attachment protein should clarify the mechanism of cell entry by these viruses.