Fusion of photoreceptor membrane vesicles

Abstract

The n-alkyl bromides with 6 to 10 carbons induce formation of vesicles of 5 to 100 micrometer diameter from the small vesicles (0.1 micrometer average diameter) produced by disruption of the discs from frog rod photoreceptors. The n-alkanes, n-alkyl iodides and n-alkyl chlorides are relatively ineffective. The formation of large vesicles is independent of calcium concentration and is distinguished from fusion processes previously reported by the large number of vesicles involved. The results reported here together with others suggest the occurrence of multiple fusion (and/or rupture-resealing) events between vesicles, induced by the n-alkyl bromides.

Formation of Giant Protein Vesicles by a Lipid Cosolvent Method

“…Ahkong et al reported that hen erythrocytes fuse on incubation with hydrocarbons 20. Mason et al subsequently reported that large native membrane vesicles (0.1–0.2 μm) from frog retinas fuse to form giant vesicles (5–100 μm) upon incubation with hydrocarbon halides, more specifically n ‐hexyl bromide 21. Key findings from this study were that 1) giant vesicles contained aqueous buffer and not oil, 2) giant vesicles did not contain large vesicles or membrane fragments and 3) giant vesicle formation arises from consecutive fusions of large vesicles rather than rupture and resealing 21.…”

“…Mason et al subsequently reported that large native membrane vesicles (0.1–0.2 μm) from frog retinas fuse to form giant vesicles (5–100 μm) upon incubation with hydrocarbon halides, more specifically n ‐hexyl bromide 21. Key findings from this study were that 1) giant vesicles contained aqueous buffer and not oil, 2) giant vesicles did not contain large vesicles or membrane fragments and 3) giant vesicle formation arises from consecutive fusions of large vesicles rather than rupture and resealing 21. Morigaki and Walde further showed that large vesicles composed of fatty acids, such as oleic acid, fuse to form giant vesicles on coverplate glass with squalane (oil) adsorbed onto the surface 22.…”

Membrane Fusion Induced by Small Molecules and Ions

“…Among them n -hexyl bromide (Figure 6; n = 6), octyl bromide ( n = 8), and decyl bromide ( n = 10) are known to have the desired fusogenic property [94]. These molecules can induce fusion at a very low molecule-to-lipid ratio (M : L) of 0.05 (for n = 6) [95], and they can induce cellular or subcellular membrane fusion [96] along with the fusion of biomimetics like PC-phosphatidic acid (PC : PA) mixed vesicles. Multilamellar vesicles (MLVs) of PC or PC : PA mixed lipids are used for experiments.…”

The Molecular Aspects of Visual Photoreceptors

“…The osmotic integrity of rod outer segments in 0.6M sucrose seemed to be stabilized by 1 mM CaCl, [ 1071. Vesicles of 5 100 pn diameter were prepared by fusion of frog disks with n-alkyl bromides [74]. Whether the fused membrane retained the same sidedness as intact disk membrane was not investigated.…”