Abstract
Animal toxins are associated with well defined selectivity profiles; however the molecular basis for this property is not understood. To address this issue we refined our previous three-dimensional models of the complex between the sea anemone toxin BgK and the S5-S6 region of Kv1.1 (Gilquin, B., Racape, J., Wrisch, A., Visan, V., Lecoq, A., Grissmer, S., Ménez, A., and Gasparini, S. (2002) J. Biol. Chem. 277, 37406-37413) using a docking procedure that scores and ranks the structures by comparing experimental and back-calculated values of coupling free energies DeltaDeltaGint obtained from double-mutant cycles. These models further highlight the interaction between residue 379 of Kv1.1 and the conserved dyad tyrosine residue of BgK. Because the nature of the residue at position 379 varies from one channel subtype to another, we explored how these natural mutations influence the sensitivity of Kv1 channel subtypes to BgK using binding and electrophysiology experiments. We demonstrated that mutations at this single position indeed suffice to abolish or enhance the sensitivity of Kv1 channels for BgK and other sea anemone and scorpion toxins. Altogether, our data suggest that the residue at position 379 of Kv1 channels controls the affinity of a number of blocking toxins.
Highlights
Molecular recognition and specific association of protein ligands and protein targets are central to most biological processes
We have previously studied in detail BgK, a 37-amino acid peptide isolated from the sea anemone Bunodosoma granulifera (7), which binds with similar high affinity to Kv1.1, Kv1.2, and Kv1.6 (8) but not to Kv1.4 and Kv1.5 channels
One of the main goals of studying protein-protein interactions is to understand the molecular basis of selectivity or, in other words, how a protein ligand can display large differences in affinity for closely related receptors
Summary
Modeling of the Complex BgK1⁄7S5-S6 Region of Kv1.1—BgK was docked onto a structural model of Kv1.1 using distance restraints derived from double-mutant cycles (9) according to a procedure similar to that developed in Eriksson and Roux (18). In a second step hydrogen atoms were introduced, and the system was annealed from 800 to 400 K in 10,000 steps During these two steps distance restraint force constants were set to 20, 10, 2 kcal/mol for the strong, medium, and weak constraints, respectively. In a final step the structures were refined by slow cooling from 800 to 300 K in 8000 steps during which the distance restraint force constants were reduced to 5, 2, and 0.5 kcal for the strong, medium, and weak constraint, respectively. The best structures in terms of van der Waals interaction energy were selected For these structures the ⌬⌬Gint from double-mutant cycles were back-calculated using a continuous implicit solvent model based on the Poisson-Boltzmann equation (18).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
