title: Two distinct trimeric conformations of natively membrane-anchored full-length herpes simplex virus 1 glycoprotein B.
abstract: Many viruses are enveloped by a lipid bilayer acquired during assembly, which is typically studded with one or two types of glycoproteins. These viral surface proteins act as the primary interface between the virus and the host. Entry of enveloped viruses relies on specialized fusogen proteins to help merge the virus membrane with the host membrane. In the multicomponent herpesvirus fusion machinery, glycoprotein B (gB) acts as this fusogen. Although the structure of the gB ectodomain postfusion conformation has been determined, any other conformations (e.g., prefusion, intermediate conformations) have so far remained elusive, thus restricting efforts to develop antiviral treatments and prophylactic vaccines. Here, we have characterized the full-length herpes simplex virus 1 gB in a native membrane by displaying it on cell-derived vesicles and using electron cryotomography. Alongside the known postfusion conformation, a novel one was identified. Its structure, in the context of the membrane, was determined by subvolume averaging and found to be trimeric like the postfusion conformation, but appeared more condensed. Hierarchical constrained density-fitting of domains unexpectedly revealed the fusion loops in this conformation to be apart and pointing away from the anchoring membrane. This vital observation is a substantial step forward in understanding the complex herpesvirus fusion mechanism, and opens up new opportunities for more targeted intervention of herpesvirus entry.
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom;
authors.forename: Tzviya
authors.initials: T
authors.lastname: Zeev-Ben-Mordehai
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom;
authors.forename: Daven
authors.initials: D
authors.lastname: Vasishtan
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom; Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, London WC1E 7HX, United Kingdom.
authors.forename: Anna
authors.initials: A
authors.lastname: Hernández Durán
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom;
authors.forename: Benjamin
authors.initials: B
authors.lastname: Vollmer
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom;
authors.forename: Paul
authors.initials: P
authors.lastname: White
authors.affiliation: Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, London WC1E 7HX, United Kingdom.
authors.forename: Arun
authors.initials: A
authors.lastname: Prasad Pandurangan
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom;
authors.forename: C Alistair
authors.initials: CA
authors.lastname: Siebert
authors.affiliation: Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, London WC1E 7HX, United Kingdom.
authors.forename: Maya
authors.initials: M
authors.lastname: Topf
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom; kay@strubi.ox.ac.uk.
authors.forename: Kay
authors.identifier: http://orcid.org/0000-0002-4788-2691
authors.initials: K
authors.lastname: Grünewald
mesh_terms: D020285:Cryoelectron Microscopy; D018259:Herpesvirus 1, Human / Q000737:chemistry*; D008562:Membrane Glycoproteins / Q000737:chemistry*; D011487:Protein Conformation; D014759:Viral Envelope Proteins / Q000737:chemistry*
chemical_list: D008562:Membrane Glycoproteins; D014759:Viral Envelope Proteins
keywords: class III viral fusion protein; electron cryotomography; membrane fusion; prefusion conformation; subvolume averaging