title: Serine-scanning mutagenesis studies of the C-terminal heptad repeats in the SARS coronavirus S glycoprotein highlight the important role of the short helical region.
abstract: The fusion subunit of the SARS-CoV S glycoprotein contains two regions of hydrophobic heptad-repeat amino acid sequences that have been shown in biophysical studies to form a six-helix bundle structure typical of the fusion-active core found in Class I viral fusion proteins. Here, we have applied serine-scanning mutagenesis to the C-terminal-most heptad-repeat region in the SARS-CoV S glycoprotein to investigate the functional role of this region in membrane fusion. We show that hydrophobic sidechains at a and d positions only within the short helical segment of the C-terminal heptad-repeat region (I1161, I1165, L1168, A1172, and L1175) are critical for cell-cell fusion. Serine mutations at outlying heptad-repeat residues that form an extended chain in the core structure (V1158, L1179, and L1182) do not affect fusogenicity. Our study provides genetic evidence for the important role of alpha-helical packing in promoting S glycoprotein-mediated membrane fusion.
authors.affiliation: Montana Biotechnology Center, The University of Montana, Science Complex Room 221, Missoula, MT 59812, USA.
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Follis
authors.forename: Joanne
authors.initials: J
authors.lastname: York
authors.forename: Jack H
authors.initials: JH
authors.lastname: Nunberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D008561:Membrane Fusion / Q000235:genetics / Q000502:physiology; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D020449:Repetitive Sequences, Amino Acid; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*; D064370:Spike Glycoprotein, Coronavirus; D014162:Transfection; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology
chemical_list: D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV