title: VSV transmembrane domain (TMD) peptide promotes PEG-mediated fusion of liposomes in a conformationally sensitive fashion.
abstract: Helical instability induced by gly residues in the transmembrane domain (TMD) of G protein, the fusion protein of vesicular stomatitis virus (VSV), was speculated to aid in the later steps of the fusion process, because G protein with ala's substituted for the two TMD gly's was inactive (Cleverley, D. Z., and Lenard, J. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 3425-30). Here we examine the conformations of synthetic peptides corresponding to fusion-active (GGpep) and inactive (AApep; G's replaced by A's) TMDs by CD spectroscopy, and then their effects on the kinetics of poly (ethyleneglycol) (PEG)-mediated fusion of small unilamellar vesicles. GGpep and AApep both assumed history-dependent, non-interconvertible ordered structures. Both peptides were largely helical under all conditions if derived from trifluoroethanol solutions, and aggregated in a beta-sheet form if derived from acetonitrile solutions. In solvent, detergents or lipid bilayers, GGpep showed a greater range of secondary structural features than did AApep. The two peptides had large but different effects on PEG-mediated fusion. Both enhanced the rate but not the extent of lipid mixing. AApep significantly inhibited the extent of fusion pore formation while GGpep had no effect. The initial rate of fusion was enhanced 6-fold by GGpep and less than 2-fold by AApep. Addition of 5 mol % hexadecane overrode all peptide-induced effects. We suggest that both GGpep and hexadecane promote pore formation by stabilizing the nonlamellar structures in fusion intermediates or initial small pores. AApep, which had fewer nonhelical features in its CD spectrum than GGpep, actually inhibited fusion pore formation.
authors.affiliation: Department of Biochemistry & Program in Molecular/Cell Biophysics, University of North Carolina, Chapel Hill, 27599-7260, USA.
authors.forename: S Moses
authors.initials: SM
authors.lastname: Dennison
authors.forename: Norma
authors.initials: N
authors.lastname: Greenfield
authors.forename: John
authors.initials: J
authors.lastname: Lenard
authors.forename: Barry R
authors.initials: BR
authors.lastname: Lentz
mesh_terms: D000473:Alkanes / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D002236:Carbohydrate Conformation; D002784:Cholesterol / Q000737:chemistry; D002942:Circular Dichroism; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry*; D008561:Membrane Fusion; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013109:Sphingomyelins / Q000737:chemistry; D014721:Vesicular stomatitis Indiana virus / Q000737:chemistry* / Q000235:genetics; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; D000473:Alkanes; C028391:G protein, vesicular stomatitis virus; D008081:Liposomes; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D013109:Sphingomyelins; D014759:Viral Envelope Proteins; D014760:Viral Fusion Proteins; D011092:Polyethylene Glycols; D002784:Cholesterol; C017251:1,2-oleoylphosphatidylcholine; C007932:n-hexadecane