Proper maturation of the Japanese encephalitis virus envelope glycoprotein requires cosynthesis with the premembrane protein.

The role of the Japanese encephalitis virus (JEV) premembrane (prM) protein in maturation of the envelope (E) glycoprotein was evaluated by using recombinant vaccinia viruses encoding E in the presence (vP829) or absence (vP658) of prM. Immunofluorescence analyses showed that E appeared to be localized in the endoplasmic reticulum of cells infected with JEV, vP829, or vP658. However, reactivity with monoclonal antibodies and behavior in Triton X-114 indicated that E produced in the absence of prM behaved abnormally. Furthermore, E produced in the presence of prM by recombinant vaccinia viruses could be incorporated into flavivirus pseudotypes, whereas E synthesized in the absence of prM could not. These results demonstrate that cosynthesis of prM is required for proper folding, membrane association, and assembly of the flavivirus E protein.