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Engineered Passive Potassium Conductance in the KR2 Sodium Pump
Arend Vogt1, Arita Silapetere1, Christiane Grimm1
1Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany.
Biophysical Journal
|May 1, 2019
Summary
Molecular engineering transforms light-driven sodium pumps into cation channels. Mutations enable passive ion flow, offering new tools for optogenetics and ion transport research.
Area of Science:
- Microbial rhodopsins
- Optogenetics
- Ion transport mechanisms
Background:
- Light-driven sodium pumps (NaRs) are microbial rhodopsins that harness light energy for active sodium ion extrusion.
- Understanding NaR function is crucial for developing novel optogenetic tools.
Purpose of the Study:
- To engineer light-driven sodium pumps into light-activated cation channels.
- To investigate the molecular determinants of ion selectivity and transport in engineered NaRs.
Main Methods:
- Targeted mutagenesis of Dokdonia eikasta (KR2) sodium pump.
- Electrophysiological recordings in living cells.
- Analysis of ion selectivity and photocurrents under varying conditions.
Main Results:
- Introduction of R109Q mutation in KR2 created passive ion conductance, preferring potassium over sodium.
- Modifications to KR2 counterion complex and other residues enhanced channel-like activity and reduced residual sodium pumping.
- Channel activity required deprotonation of counterions (D116, D251) under alkaline conditions.
Conclusions:
- Specific mutations can convert NaRs into light-activated cation channels with altered ion selectivity.
- Interactions between key residues (R109, L75, S70, D116, D251) regulate ion transport and prevent passive backflow.
- Engineered NaRs offer a versatile platform for optogenetic applications and studying ion transport.
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