title: Characterization of monomeric intermediates during VSV glycoprotein structural transition.
abstract: Entry of enveloped viruses requires fusion of viral and cellular membranes, driven by conformational changes of viral glycoproteins. Crystal structures provide static pictures of pre- and post-fusion conformations of these proteins but the transition pathway remains elusive. Here, using several biophysical techniques, including analytical ultracentrifugation, circular dichroïsm, electron microscopy and small angle X-ray scattering, we have characterized the low-pH-induced fusogenic structural transition of a soluble form of vesicular stomatitis virus (VSV) glycoprotein G ectodomain (G(th), aa residues 1-422, the fragment that was previously crystallized). While the post-fusion trimer is the major species detected at low pH, the pre-fusion trimer is not detected in solution. Rather, at high pH, G(th) is a flexible monomer that explores a large conformational space. The monomeric population exhibits a marked pH-dependence and adopts more elongated conformations when pH decreases. Furthermore, large relative movements of domains are detected in absence of significant secondary structure modification. Solution studies are complemented by electron micrographs of negatively stained viral particles in which monomeric ectodomains of G are observed at the viral surface at both pH 7.5 and pH 6.7. We propose that the monomers are intermediates during the conformational change and thus that VSV G trimers dissociate at the viral surface during the structural transition.
authors.affiliation: Centre de Recherche de Gif, Laboratoire de Virologie Moléculaire et Structurale, CNRS (UPR 3296), Gif sur Yvette, France.
authors.forename: Aurélie A
authors.initials: AA
authors.lastname: Albertini
authors.forename: Cécile
authors.initials: C
authors.lastname: Mérigoux
authors.forename: Sonia
authors.initials: S
authors.lastname: Libersou
authors.forename: Karine
authors.initials: K
authors.lastname: Madiona
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bressanelli
authors.forename: Stéphane
authors.initials: S
authors.lastname: Roche
authors.forename: Jean
authors.initials: J
authors.lastname: Lepault
authors.forename: Ronald
authors.initials: R
authors.lastname: Melki
authors.forename: Patrice
authors.initials: P
authors.lastname: Vachette
authors.forename: Yves
authors.initials: Y
authors.lastname: Gaudin
mesh_terms: D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D055503:Protein Multimerization; D017433:Protein Structure, Secondary / Q000502:physiology; D018116:Vesiculovirus / Q000737:chemistry / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000378:metabolism; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D014771:Virion / Q000378:metabolism
chemical_list: D008081:Liposomes; D008562:Membrane Glycoproteins; D014759:Viral Envelope Proteins; D014760:Viral Fusion Proteins