Voltage-gating and assembly of split Kv10.1 channels

by Adam Tomczak
Doctoral thesis
Date of Examination:2016-04-22
Date of issue:2016-07-04
Advisor:Dr. Luis A. Pardo
Referee:Dr. Luis A. Pardo
Referee:Prof. Dr. Tobias Moser
Persistent Address: http://dx.doi.org/10.53846/goediss-5630

 

 

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Abstract

English

Voltage-gated ion channels allow ions to pass cell membrane upon changes of transmembrane electrical potential. Conformational changes in the voltage-sensing domain of the channel (VSD) are assumed to be transmitted to the pore domain (PD) through an alpha-helical linker between them (S4-S5 linker). We have previously shown that expression of VSD and PD as separate fragments results in functional Kv10.1 channels that retain voltage-dependence. Here we used such ‘split’ channels to investigate functional interactions between VSD and PD. We found that their electrophysiological properties greatly depend on where the S4-S5 linker is interrupted. Remarkably, wild-type-like channel behavior could be fully or largely restored by mutations of crucial linker amino acids, indicating that precise functional interactions between VSD and PD remain when they are not covalently bound. Voltage-Clamp Fluorometry measurements revealed that VSD motion is alerted in specific split channels, but these changes were subtler. Finally, the increased separation between VSD activation and channel opening in the split channel carrying a large deletion in the S4-S5 linker, as well as the failure of the PD expressed alone to give currents, suggest that the role of the VSD in the is to open the channel pore and prevent it from closing.
Keywords: biophysics; potassium channels; voltage-gating; voltage-gated ion channels
 
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