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Insect nervous system [(3)H]saxitoxin binding sites: characterization and target size.
1AFRC Unit of Insect Neurophysiology and Pharmacology, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, England.
Neurochemistry International
|May 28, 2010
Summary
Saxitoxin (STX) binding in cockroach nervous system membranes reveals specific sites on voltage-operated sodium channels. Radiation inactivation estimates the insect sodium channel
Area of Science:
- Neuroscience
- Biochemistry
- Pharmacology
Background:
- Saxitoxin (STX) is a critical tool for studying voltage-operated sodium channels in various organisms.
- Cockroach (Periplaneta americana) nervous system membranes exhibit specific [(3)H]STX binding, indicating the presence of these channels.
Purpose of the Study:
- To characterize the specific saxitoxin binding sites in the cockroach nervous system.
- To determine the molecular size of the insect sodium channel using radiation inactivation.
Main Methods:
- Radioligand binding assays using [(3)H]STX.
- Scatchard analysis to determine binding affinity (K(D)) and site density (B(max)).
- Radiation inactivation to estimate the molecular weight (M(r)) of the target protein.
Main Results:
- Specific [(3)H]STX binding was identified with a K(D) of 0.84 nM and B(max) of 8.25 pmol/mg protein.
- Binding was inhibited by STX and tetrodotoxin (TTX), confirming specificity for the sodium channel.
- Radiation inactivation yielded an estimated M(r) of 171,400 +/- 25,000 for the insect sodium channel.
Conclusions:
- The cockroach nervous system possesses specific saxitoxin binding sites associated with voltage-operated sodium channels.
- The estimated molecular weight provides insights into the structure of insect sodium channels.
