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 used for Figures 2 to 7 is available in dryad.org
Data from: Trans-toxin ion-sensitivity of charybdotoxin-blocked potassium-channels reveals unbinding transitional statesDryad Digital Repository, doi:10.5061/dryad.0p77qk4.
- Hans Moldenhauer
- Ignacio Díaz-Franulic
- Horacio Poblete
- Horacio Poblete
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Leon D Islas, Universidad Nacional Autónoma de México, Mexico
© 2019, Moldenhauer et al.
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