Viral entry mechanisms: the increasing diversity of paramyxovirus entry

The paramyxovirus family contains established human pathogens such as the measles virus and human respiratory syncytial virus, as well as emerging pathogens including the Hendra and Nipah viruses and the recently identified human metapneumovirus. Two major envelope glycoproteins, the attachment protein and the fusion protein, promote the processes of viral attachment and virus-cell membrane fusion required for entry. Although common mechanisms of fusion protein proteolytic activation and the mechanism of membrane fusion promotion have been shown in recent years, considerable diversity exists in the family relating to receptor binding and the potential mechanisms of fusion triggering.