ORCiD

Nejat Düzgüneş: 0000-0001-6159-1391

Document Type

Article

Publication Title

Biochimica et Biophysica Acta - Biomembranes

ISSN

0005-2736

Volume

693

Issue

1

DOI

10.1016/0005-2736(82)90474-6

First Page

93

Last Page

98

Publication Date

12-8-1982

Abstract

We have examined the early events in Ca2+-induced fusion of large (0.2 μm diameter) unilamellar cardiolipin/phosphatidylcholine and phosphatidylserine/phosphatidylethanolamine vesicles by quick-freezing freeze-fracture electron microscopy, eliminating the necessity of using glycerol as a cryoprotectant. Freeze-fracture replicas of vesicle suspensions frozen after 1-2 s of stimulation revealed that the majority of vesicles had already undergone membrane fusion, as evidenced by dumbbell-shaped structures and large vesicles. In the absence of glycerol, lipidic particles or the hexagonal HII phase, which have been proposed to be intermediate structures in membrane fusion, were not observed at the sites of fusion. Lipidic particles were evident in less than 5% of the cardiolipin/phosphatidylcholine vesicles after long-term incubation with Ca2+, and the addition of glycerol produced more vesicles displaying the particles. We have also shown that rapid fusion occurred within seconds of Ca2+ addition by the time-course of fluorescence emission produced by the intermixing of aqueous contents of two separate vesicle populations. These studies therefore have produced no evidence that lipidic particles are necessary intermediates for membrane fusion. On the contrary, they indicate that lipidic particles are structures obtained at equilibrium long after fusion has occurred and they become particularly prevalent in the presence of glycerol. © 1982.

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Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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