FIG. 1.

Flavivirus E protein conformational transition associated with membrane fusion [adapted from Stiasny and Heinz (53)]. Before fusion (at left), E forms a dimer oriented parallel to the viral envelope membrane. Low pH induces a conformational change, including the repositioning of domain III (blue) alongside domain 1 (red) and rotation of domain II (yellow), including the fusion peptide, toward the host cell membrane. After fusion, E forms a trimer oriented perpendicular to the membrane (at right). E, envelope.