Fusion of Sendai virus with negatively charged liposomes as studied by pyrene-labelled phospholipid liposomes

Shimon Amselem, Yechezkel Barenholz, Abraham Loyter, Shlomo Nir, Dov Lichtenberg*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Sendai virus particles fuse with negatively charged liposomes but not with vesicles made of zwitterionic phospholipids. The liposome-virus fusion process was studied by dilution of the concentration-dependent excimer-forming fluorophore 2-pyrenyldodecanoylphosphatidylcholine contained in the liposomes by the viral lipids. The data were analyzed in the framework of a mass action kinetic model. This provided analytical solutions for the final levels of probe dilution and numerical solutions for the kinetics of the overall fusion process, in terms of rate constants for the liposome-virus adhesion, deadhesion and fusion. This analysis led to the following conclusions: (1) At neutral pH and 37°C, only 15% of the virus particles can fuse with the phospholipid vesicles, although all the virions may aggregate with the liposomes. The rate constants for aggregation, fusion and deadhesion are of the orders of magnitude of 107 M-1 · s-1, 10-3 s-1 and 10-2 s-1, respectively. The fraction of active virus increases with temperature. (2) At acidic pH, both the fraction of 'fusable' virus and the rate of fusion increase markedly. The optimal pH for fusion is 3-4, where most of the virus particles are active. At higher pH values, an increasing fraction of the virus particles become inactive, probably due to ionization of viral glycoproteins, whereas at pH values below 3.0 the fusion is markedly reduced, most likely due to protonation of the negatively charged vesicles. (3) While only 15% of the virions fuse with the liposomes at pH 7.4 and 37°C, all the liposomes lose their content (Amselem, S., Loyter, A. Lichtenberg, D. and Barenholz, Y. (1985) Biochim. Biophys. Acta 820, 1-10). We therefore propose that release of entrapped solutes is due to liposome-virus aggregation, and not to fusion. Both trypsinization and heat inactivation of the virus particles inhibit not only the fusion process but also the release of carboxyfluorescein. This demonstrates the obligatory role of viral membrane proteins in liposome-virus aggregation. (4) Reconstituted vesicles made of the viral lipid and the hemagglutinin/ neuraminidase (HN) glycoprotein fuse with negatively charged liposomes similar to the intact virions. This suggests that the fusion of virions with negatively charged vesicles, unlike the fusion of the virus with biological membranes, requires only the HN and not the fusion glycoprotein.

Original languageEnglish
Pages (from-to)301-313
Number of pages13
JournalBBA - Biomembranes
Issue number2
StatePublished - 21 Aug 1986


FundersFunder number
Joint Research Fund of lhe Hebrew Univerfity
United S~I~ad Bination~ Sdence Foundation
National Heart, Lung, and Blood InstituteR01HL017576
Bloom's Syndrome FoundationPHS-NIH-HL 17576


    • Fluorescence
    • Kinetics
    • Liposome charge
    • Membrane fusion
    • Membrane-virus interaction
    • Sendai virus


    Dive into the research topics of 'Fusion of Sendai virus with negatively charged liposomes as studied by pyrene-labelled phospholipid liposomes'. Together they form a unique fingerprint.

    Cite this