A novel membrane fusion protein family in Flaviviridae?

Highlights: [•] Viral membrane fusion proteins fall into three distinct structural classes (I–III). [•] In 2013, the E2 glycoproteins of pesti- and hepaciviruses were found to have novel folds. [•] E1 and E2 proteins of pesti- and hepaciviruses define a new class of fusion machinery. [•] Structural data suggest that fusion proteins evolved by host–virus or virus–virus transfer. [ABSTRACT FROM AUTHOR]