The first structure of a flavivirus has been determined by using a combination of cryoelectron microscopy and fitting of the known structure of glycoprotein E into the electron density map. The virus core, within a lipid bilayer, has a less-ordered structure than the external, icosahedral scaffold of 90 glycoprotein E dimers. The three E monomers per icosahedral asymmetric unit do not have quasiequivalent symmetric environments. Difference maps indicate the location of the small membrane protein M relative to the overlaying scaffold of E dimers. The structure suggests that flaviviruses, and by analogy also alphaviruses, employ a fusion mechanism in which the distal β barrels of domain II of the glycoprotein E are inserted into the cellular membrane.
Bibliographical noteFunding Information:
We thank Sharon Wilder for help in preparation of the manuscript. The work was supported by a National Institutes of Health Program Project Grant to M.G.R., R.J.K., and T.S.B. (AI45976), grant AI20612 to J.H.S., grant AI10793 to J.H.S. and E.G.S., and a Purdue University redevelopment award. C.T.J. is a recipient of a National Institutes of Health biophysics training grant (GM08296).