Characterization of the Ptychodiscus Brevis Polyether Neurotoxin Binding Component in Excitable Membranes
Abstract
The brevetoxins bind to a unique receptor site associated with excitable membranes. The site, which possesses a Kd of 2.6-3.3 nM and a Bmax of 5.75-6.0 pmoles/mg protein, is present in rat, fish, and turtle synaptosomes. This high affinity, low capacity site, is accompanied by a lower affinity, higher capacity site which is currently under investigation. The high affinity site is known as site 5, and binds toxin with half-maximal affinity and avidity at concentrations which yield half-maximal 22Na ion influx and half-maximal nerve membrane depolarization. Toxin binding at this high affinity site is membrane potential independent and does not interact with any of the previously described sodium channel binding sites. The binding characteristics of the lower affinity site correlate well with observed allosteric modulation observed in sites 1-4 of the voltage-sensitive sodium channel. Photoaffinity probes incorporating brevetoxin in a covalent form displace brevetoxin from the binding site of high affinity, underscoring their potential as specific probes for purification of the site. Both size chromatography and brevetoxin-affinity columns, following solubilization of the site from membranes holds promise for isolation, purification, and characterization of the specific site. Keywords: Marine toxins, Sodium channels, Pharmacology.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1988
- Accession Number
- ADA200959
Entities
People
- Daniel G. Baden
- Thomas J. Mende
Organizations
- University of Miami