Trans-toxin ion-sensitivity of charybdotoxin-blocked potassium-channels reveals unbinding transitional states

Abstract
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Abstract

In-silico and in-vitro studies have made progress in understanding protein-protein complexes formation; however, the molecular mechanisms for their dissociation are unclear. Protein-protein complexes, lasting from microseconds to years, often involve induced-fit, challenging computational or kinetic analysis. Charybdotoxin (CTX), a peptide from the Leiurus scorpion venom, blocks voltage-gated K⁺-channels in a unique example of binding/unbinding simplicity. CTX plugs the external mouth of K⁺-channels pore, stopping K⁺-ion conduction, without inducing conformational changes. Conflicting with a tight binding, we show that external permeant ions enhance CTX-dissociation, implying a path connecting the pore, in the toxin-bound channel, with the external solution. This sensitivity is explained if CTX wobbles between several bound conformations, producing transient events that restore the electrical and ionic trans-pore gradients. Wobbling may originate from a network of contacts in the interaction interface that are in dynamic stochastic equilibria. These partially-bound intermediates could lead to distinct, and potentially manipulable, dissociation pathways.

Data availability

Data used for Figures 2 to 7 is available in dryad.org

The following data sets were generated

(2019) Data from: Trans-toxin ion-sensitivity of charybdotoxin-blocked potassium-channels reveals unbinding transitional states
Dryad Digital Repository, doi:10.5061/dryad.0p77qk4.

https://doi.org/10.5061/dryad.0p77qk4

Article and author information

Author details

Hans Moldenhauer

Instituto de Neurociencia, Universidad de Valparaíso, Valpararaíso, Chile

Competing interests
The authors declare that no competing interests exist.
Ignacio Díaz-Franulic

Instituto de Neurociencia, Universidad de Valparaíso, Valparaíso, Chile

Competing interests
The authors declare that no competing interests exist.
Horacio Poblete

Center for Bioinformatics and Molecular Simulations, Universidad de Talca, Talca, Chile

Competing interests
The authors declare that no competing interests exist.
David Naranjo

Instituto de Neurociencia, Universidad de Valparaíso, Valparaíso, Chile

For correspondence
david.naranjo@uv.cl

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-3482-5126

Funding

Fondo Nacional de Desarrollo Científico y Tecnológico (3160321)

Hans Moldenhauer

Fondo Nacional de Desarrollo Científico y Tecnológico (3170599)

Ignacio Díaz-Franulic

Fondo Nacional de Desarrollo Científico y Tecnológico (1171155)

Horacio Poblete

Ministerio de Economía, Fomento y Turismo (MiNICAD)

Horacio Poblete

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.