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Molecular size of different neurotoxin receptors on the voltage-sensitive Na+ channel
Abstract:
Measurements were made of the molecular sizes of two distinct receptors on the Na+ channel in rat brain synaptosomes that are specific for different neurotoxins. Radiation inactivation of the binding of radiolabeled derivatives of the toxins was consistent with Mr = 260,000 for the tetrodotoxin receptor and Mr = 266,000 for the receptor specific for two scorpion toxins, toxin II from Centruroides suffusus suffusus and toxin gamma from Tityus serrulatus serrulatus. Covalent cross-linking of the latter to its receptor similarly indicated Mr = 270,000. It seems most likely that these two distinct receptors reside on the same molecule.
Insights
Researchers measured the molecular sizes of neurotoxin receptors on rat brain sodium channels. Findings suggest distinct tetrodotoxin and scorpion toxin receptors are likely part of the same large protein molecule.
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- Sodium channels are crucial for neuronal function.
- Specific neurotoxins bind to distinct sites on sodium channels.
- Understanding receptor structure is key to neuropharmacology.
Purpose of the Study:
- To determine the molecular size of neurotoxin-specific receptors on rat brain sodium channels.
- To investigate whether these distinct receptors are located on the same or different molecular entities.
Main Methods:
- Radiation inactivation assays were used to estimate the molecular weight (Mr) of toxin-binding sites.
- Covalent cross-linking was employed to further characterize receptor size and association.
Main Results:
- The tetrodotoxin receptor exhibited an Mr of approximately 260,000.
- Receptors for two scorpion toxins (from Centruroides suffusus suffusus and Tityus serrulatus serrulatus) showed an Mr of approximately 266,000.
- Covalent cross-linking indicated a similar Mr of 270,000 for the scorpion toxin receptor.
Conclusions:
- The molecular sizes determined by radiation inactivation and cross-linking are similar.
- Evidence strongly suggests that the tetrodotoxin and scorpion toxin receptors are located on the same large molecular complex.