Ganglioside composition of subcellular fractions,including pre- and postsynaptic membranes,fromTorpedo electric organ

Gangliosides were isolated from four subcellular fractions of the electric organ ofTorpedo marmorata: synaptosomes, presynaptic membranes, postsynaptic membranes, and synaptic vesicle membranes. This exploited a principal advantage offered by this tissue: facile separation of pre-and postyynaptic elements. Total ganglioside concentration in presynaptic membranes was approximately twice that of synaptosomes and 15 times that of postsynaptic membranes (47.7, 24.4, and 3.21 g of lipid sialic acid per mg protein, respectively). Synaptic vesicle membranes had the highest overall concentration (78.9) relative to protein, but a concentration approximately comparable to that of presynaptic membranes when expressed relative to phospholipid. The thin-layer patterns of these two fractions were similar, both in terms of total pattern and the specific pattern of gangliotetraose structures as revealed by overlay with cholera toxin B subunit; these were notable for the paucity of monosialo structures and the virtual absence of GM1. Postsynaptic membranes, on the other hand, had a significantly higher content of monosialogangliosides including the presence of GM1. The synaptosomal pattern resembled that of the presynaptic membranes and synaptic vesicles. Thus, a clear difference in ganglioside pattern could be discerned between the pre- and postsynaptic elements of the electric organ.Abbreviations SVs synaptic vesicles - TLC thin-layer chromatography - cholera B-HRP B subunit of cholera toxin linked to horseradish peroxidase