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The incorporation in vitro of sulphate ions into synaptic-membrane glycoproteins
Abstract:
Synaptosomes from sheep brain cortex were incubated with carrier-free Na235SO4 and the synaptic plasma membranes were isolated. The membranes were free of contamination from cytosol, mitochondria and microsomal material and accounted for 30% of the radioactivity present in the synaptosomal particulate fraction. Control experiments demonstrated that the radioactivity present in the preparation was not due to non-specific binding of sulphate ions. The synaptic membranes contained at least six 35S-containing protein bands with molecular weights between 160 000 and 16 000. Analysis showed that the radioactivity was located in the carbohydrate moiety of a glycopeptide.
Insights
Sheep brain synaptosomes incorporated sodium sulfate (Na235SO4), revealing 35S-labeled glycopeptides in synaptic membranes. This study identifies specific sulfate incorporation into brain synaptic membrane proteins.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Synaptosomes are crucial for studying neuronal function and neurotransmitter release.
- Understanding the molecular composition of synaptic plasma membranes provides insights into neuronal signaling.
Purpose of the Study:
- To investigate the incorporation and localization of sulfate within sheep brain synaptosomes.
- To identify proteins within the synaptic plasma membrane that bind sulfate.
Main Methods:
- Isolation of synaptosomes from sheep brain cortex.
- Incubation with carrier-free sodium sulfate (Na235SO4).
- Purification of synaptic plasma membranes and analysis of incorporated radioactivity.
Main Results:
- Isolated synaptic plasma membranes contained 30% of the radioactivity from the synaptosomal particulate fraction.
- Radioactivity was confirmed not to be due to non-specific sulfate binding.
- Six distinct 35S-containing protein bands (160,000–16,000 MW) were identified in synaptic membranes.
- Analysis revealed that the incorporated 35S was located in the carbohydrate moiety of a glycopeptide.
Conclusions:
- Synaptic plasma membranes of sheep brain cortex incorporate sulfate.
- Sulfate is covalently bound to the carbohydrate portion of glycopeptides within the synaptic membrane.
- These findings contribute to understanding the post-translational modification and molecular makeup of synaptic structures.