Summary
Two sensitive fluorescence lipid-mixing assays were used to study the fusion of isolated chromaffin granules. Intermixing of membrane lipids was found to be the rate-limiting step in the fusion process. The threshold Ca2+ concentration for fusion was 1 mM in the absence of mediator protein, but 10 μM in the presence of synexin or 32K calelectrin. Cis-unsaturated free fatty acids increased both the magnitude of the fusion response and its sensitivity to Ca2+ to within the micromolar range. Fusion required an intact, native chromaffin granule and was inhibited by hypertonic medium. High concentrations of synexin or calelectrin also inhibited granule fusion, but not granule aggregation. The properties of these proteins suggest they may play a specific role in promoting membrane fusion in exocytosis.
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© 1988 Plenum Press, New York
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Zaks, W.J., Creutz, C.E. (1988). Membrane Fusion in Model Systems for Exocytosis: Characterization of Chromaffin Granule Fusion Mediated by Synexin and Calelectrin. In: Ohki, S., Doyle, D., Flanagan, T.D., Hui, S.W., Mayhew, E. (eds) Molecular Mechanisms of Membrane Fusion. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-1659-6_24
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DOI: https://doi.org/10.1007/978-1-4613-1659-6_24
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