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. 1992 May 15;89(10):4749–4753. doi: 10.1073/pnas.89.10.4749

Proteins on exocytic vesicles mediate calcium-triggered fusion.

S S Vogel 1, J Zimmerberg 1
PMCID: PMC49161  PMID: 1584814

Abstract

In many exocytic systems, micromolar concentrations of intracellular Ca2+ trigger fusion. We find that aggregates of secretory granules isolated from sea urchin eggs fuse together when perfused with greater than or equal to 10 microM free Ca2+. Mixing of membrane components was demonstrated by transfer of fluorescent lipophilic dye, and melding of granule contents was seen with differential interference microscopy. A technique based upon light scattering was developed to conveniently detect fusion. Two protein modifiers, trypsin and N-ethylmaleimide, inhibit granule-granule fusion at concentrations similar to those that inhibit granule-plasma membrane fusion. We suggest that molecular machinery sufficient for Ca(2+)-triggered fusion resides on secretory granules as purified and that at least some of these essential components are proteinaceous.

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Selected References

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