Fusion of dioleoylphosphatidylcholine vesicles induced by an amphiphilic cationic peptide and oligophosphates at neutral pH.
Peptide E5 is an analogue of the fusion peptide of influenza virus hemagglutinin and K5 is a cationic peptide which has an arrangement of electric charges complementary to that of E5. We reported that a stoichiometric mixture of E5 and K5 caused fusion of large unilamellar vesicles (LUV) of neutral phospholipids (Murata, M., Kagiwada, S., Takahashi, S. and Ohnishi, S. (1991) J. Biol. Chem. 266, 14353-14358). K5 caused fusion of LUV composed of dioleoylphosphatidylcholine (DOPC) at pH > 10, but not at neutral pH. In the presence of oligophosphates, such as 1 mM ATP, GTP, or polyphosphate, K5 caused rapid and efficient fusion of DOPC LUV at neutral pH without hydrolysis of oligophosphate groups, but another anions such as citrate, acetate, AMP, phosphate, or EDTA were ineffective. The peptide/oligophosphate-induced fusion behaviors have been investigated by a fluorescence resonance energy transfer assay for lipid mixing of LUV and negative staining electron microscopy. At higher ionic strengths ( > 0.3 M KCl) or in the presence of 5.0 mM MgCl2, the fusion was inhibited. Even at the inhibitory conditions, the association of K5 with lipid vesicles at neutral pH was directly confirmed by the Ficoll gradient assay method and by blue shifts of the tryptophan fluorescence of the peptide. A nonhydrolyzable GTP analogue, GTP gamma S, also induced fusion. These observations suggested that the electrostatic interactions between the positive and negative charges of K5 and oligophosphate, respectively, induced complex formation, triggering membrane fusion.
Murata
M
M
Faculty of Science, Kyoto University, Japan.
Shirai
Y
Y
Ishiguro
R
R
Kagiwada
S
S
Tahara
Y
Y
Ohnishi
S
S
Takahashi
S
S
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D002412:Cations / Q000737:chemistry; D002942:Circular Dichroism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D015636:Magnesium Chloride; D008561:Membrane Fusion / Q000187:drug effects*; D008854:Microscopy, Electron / Q000379:methods; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D010710:Phosphates / Q000737:chemistry / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000737:chemistry*; D011189:Potassium Chloride
D002412:Cations; C083605:K5 peptide; D010455:Peptides; D010710:Phosphates; D010713:Phosphatidylcholines; D015636:Magnesium Chloride; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D011189:Potassium Chloride; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; C017251:1,2-oleoylphosphatidylcholine