title: Cysteines flanking the internal fusion peptide are required for the avian sarcoma/leukosis virus glycoprotein to mediate the lipid mixing stage of fusion with high efficiency.
abstract: We previously showed that the cysteines flanking the internal fusion peptide of the avian sarcoma/leukosis virus subtype A (ASLV-A) Env (EnvA) are important for infectivity and cell-cell fusion. Here we define the stage of fusion at which the cysteines are required. The flanking cysteines are dispensable for receptor-triggered membrane association but are required for the lipid mixing step of fusion, which, interestingly, displays a high pH onset and a biphasic profile. Second-site mutations that partially restore infection partially restore lipid mixing. These findings indicate that the cysteines flanking the internal fusion peptide of EnvA (and perhaps by analogy Ebola virus glycoprotein) are important for the foldback stage of the conformational changes that lead to membrane merger.
authors.affiliation: Department of Cell Biology, UVA Health System, School of Medicine, P.O. Box 800732, Charlottesville, VA 22908-0732, USA. sed7a@virginia.edu
authors.forename: Sue E
authors.initials: SE
authors.lastname: Delos
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Brecher
authors.forename: Zaoying
authors.initials: Z
authors.lastname: Chen
authors.forename: Deborah C
authors.initials: DC
authors.lastname: Melder
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Federspiel
authors.forename: Judith M
authors.initials: JM
authors.lastname: White
mesh_terms: D001355:Alpharetrovirus / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D006023:Glycoproteins / Q000378:metabolism / Q000502:physiology*; D008561:Membrane Fusion; D014764:Viral Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D006023:Glycoproteins; D014764:Viral Proteins; D003545:Cysteine