Abstract
KappaM-conotoxin RIIIK blocks TSha1 K+ channels from trout with high affinity by interacting with the ion channel pore. As opposed to many other peptides targeting K+ channels, kappaM-RIIIK does not possess a functional dyad. In this study we combine thermodynamic mutant cycle analysis and docking calculations to derive the binding mode of kappaM-conotoxin RIIIK to the TSha1 channel. The final model reveals a novel pharmacophore, where no positively charged side chain occludes the channel pore. Instead the positive-charged residues of the toxin form a basic ring; kappaM-RIIIK is anchored to the K+ channel via electrostatic interactions of this basic ring with the loop and pore helix residues of the channel. The channel amino acid Glu-354 is likely to be a fundamental determinant of the selectivity of kappaM-RIIIK for the TSha1 channel. The Cgamma-OH of Hyp-15 is in contact with the carbonyls of the selectivity filter, disturbing the charge distribution pattern necessary for the coordination of K+ ions. This novel, experimentally based pharmacophore model proves the existence of diverse binding modes of peptidic toxins to K+ channels and underlines the role of intermolecular electrostatic interactions involving channel loop side chains in determining the selectivity of toxins for specific K+ channel types.
Original language | English |
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Pages (from-to) | 21246-55 |
Number of pages | 10 |
Journal | The Journal of biological chemistry |
Volume | 280 |
Issue number | 22 |
DOIs | |
Publication status | Published - 3 Jun 2005 |
Keywords
- Amino Acid Sequence
- Animals
- Cluster Analysis
- Conotoxins/chemistry
- DNA Mutational Analysis
- Electrophysiology
- Inhibitory Concentration 50
- Ions
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Mutation
- Oocytes/metabolism
- Peptides/chemistry
- Point Mutation
- Potassium/chemistry
- Potassium Channels/chemistry
- Protein Binding
- Protein Conformation
- Protein Structure, Secondary
- Software
- Static Electricity
- Thermodynamics
- Trout
- Xenopus