title: Molecular architecture of the bipartite fusion loops of vesicular stomatitis virus glycoprotein G, a class III viral fusion protein.
abstract: The glycoprotein of vesicular stomatitis virus (VSV G) mediates fusion of the viral envelope with the host cell, with the conformational changes that mediate VSV G fusion activation occurring in a reversible, low pH-dependent manner. Based on its novel structure, VSV G has been classified as class III viral fusion protein, having a predicted bipartite fusion domain comprising residues Trp-72, Tyr-73, Tyr-116, and Ala-117 that interacts with the host cell membrane to initiate the fusion reaction. Here, we carried out a systematic mutagenesis study of the predicted VSV G fusion loops, to investigate the functional role of the fusion domain. Using assays of low pH-induced cell-cell fusion and infection studies of mutant VSV G incorporated into viral particles, we show a fundamental role for the bipartite fusion domain. We show that Trp-72 is a critical residue for VSV G-mediated membrane fusion. Trp-72 could only tolerate mutation to a phenylalanine residue, which allowed only limited fusion. Tyr-73 and Tyr-116 could be mutated to other aromatic residues without major effect but could not tolerate any other substitution. Ala-117 was a less critical residue, with only charged residues unable to allow fusion activation. These data represent a functional analysis of predicted bipartite fusion loops of VSV G, a founder member of the class III family of viral fusion proteins.
authors.affiliation: Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Xiangjie
authors.initials: X
authors.lastname: Sun
authors.forename: Sandrine
authors.initials: S
authors.lastname: Belouzard
authors.forename: Gary R
authors.initials: GR
authors.lastname: Whittaker
mesh_terms: D019943:Amino Acid Substitution; D000596:Amino Acids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016297:Mutagenesis, Site-Directed; D017433:Protein Structure, Secondary / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D014709:Vero Cells; D014721:Vesicular stomatitis Indiana virus / Q000737:chemistry / Q000502:physiology*; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D053586:Virus Internalization
chemical_list: D000596:Amino Acids; D014760:Viral Fusion Proteins