title: Sequential conformational rearrangements in flavivirus membrane fusion.
abstract: The West Nile Virus (WNV) envelope protein, E, promotes membrane fusion during viral cell entry by undergoing a low-pH triggered conformational reorganization. We have examined the mechanism of WNV fusion and sought evidence for potential intermediates during the conformational transition by following hemifusion of WNV virus-like particles (VLPs) in a single particle format. We have introduced specific mutations into E, to relate their influence on fusion kinetics to structural features of the protein. At the level of individual E subunits, trimer formation and membrane engagement of the threefold clustered fusion loops are rate-limiting. Hemifusion requires at least two adjacent trimers. Simulation of the kinetics indicates that availability of competent monomers within the contact zone between virus and target membrane makes trimerization a bottleneck in hemifusion. We discuss the implications of the model we have derived for mechanisms of membrane fusion in other contexts.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States.
authors.forename: Luke H
authors.initials: LH
authors.lastname: Chao
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States.
authors.forename: Daryl E
authors.initials: DE
authors.lastname: Klein
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States.
authors.forename: Aaron G
authors.initials: AG
authors.lastname: Schmidt
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Peña
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Harrison
mesh_terms: D000330:Aedes; D000818:Animals; D002460:Cell Line; D003198:Computer Simulation; D004847:Epithelial Cells / Q000378:metabolism / Q000821:virology; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008561:Membrane Fusion / Q000235:genetics*; D008956:Models, Chemical; D016297:Mutagenesis, Site-Directed; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014771:Virion / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D053586:Virus Internalization; D014902:West Nile virus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D014759:Viral Envelope Proteins
keywords: West Nile virus; biophysics; conformational change; flavivirus; kinetics; membrane fusion; single particle; structural biology; viruses