FIG. 3.

Schematic diagram of the proposed membrane fusion process of flaviviruses. E protein: domain I in red, domain II in yellow, domain III in blue, stem region in gray, membrane anchor in green, fusion peptide loop in orange. (A) The E protein homodimer in its native state at the surface of the mature virion. (B) Low-pH-induced dissociation of the E dimer and interaction of the fusion peptide loop with the endosomal membrane. (C) Formation of an E trimer (including the flipping back of domain III) proceeding via still undefined intermediates. (D) Formation of the final postfusion conformation through interactions of the stem-anchor region with domain II, leading to the juxtaposition of the fusion peptide loops and the membrane anchors in the fused membrane.