Related Experiment Videos
A point mutation in the maxi-K clone dSlo forms a high affinity site for charybdotoxin
1Department of Pharmacology aond Physiology, University of Rochester School of Medicine and Dentistry, NY 14642-8711, USA. adric@ucla.edu
Neuropharmacology
|February 9, 2000
Summary
This study shows that a single amino acid change in the dSlo channel significantly increases its binding affinity for CTX toxin. This finding reveals a CTX receptor site on the dSlo channel.
Area of Science:
- Molecular Biology
- Ion Channel Physiology
- Biochemistry
Background:
- Maxi-K channels (dSlo and hSlo) are crucial for regulating cellular excitability.
- CTX toxin is known to interact with ion channels, but its precise binding site and affinity for dSlo were unclear.
Purpose of the Study:
- To investigate the interaction between CTX toxin and cloned maxi-K channel analogues, dSlo and hSlo.
- To identify the molecular determinants of CTX binding to the dSlo channel.
Main Methods:
- Single channel electrophysiology in lipid bilayers.
- Site-directed mutagenesis of the dSlo channel.
- Kinetic analysis of toxin-channel interactions.
Main Results:
- Wild-type dSlo showed weak binding to CTX (K(D) = 5.8 microM), while hSlo exhibited high affinity (K(D) = 36 nM).
- A dSlo mutant with threonine at position 290 replaced by glutamate displayed significantly enhanced CTX binding (K(D) = 23 nM).
- This affinity increase was primarily due to a reduced dissociation rate of CTX from the mutant channel.
Conclusions:
- A CTX receptor site exists within the dSlo channel.
- The threonine residue at position 290 in dSlo plays a critical role in destabilizing CTX binding.
- This single residue mutation alters CTX-dSlo interaction affinity over 100-fold.