Helical jackknives control the gates of the double-pore K+ uptake system KtrAB

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Abstract

Ion channel gating is essential for cellular homeostasis and is tightly controlled. In some eukaryotic and most bacterial ligand-gated K⁺ channels, RCK domains regulate ion fluxes. Until now, a single regulatory mechanism has been proposed for all RCK-regulated channels, involving signal transduction from the RCK domain to the gating area. Here we present an inactive ADP-bound structure of KtrAB from Vibrio alginolyticus, determined by cryo-electron microscopy, which, combined with EPR spectroscopy and molecular dynamics simulations, uncovers a novel regulatory mechanism for ligand-induced action at a distance. Exchange of activating ATP to inactivating ADP triggers short helical segments in the K⁺-translocating KtrB dimer to organize into two long helices that penetrate deeply into the regulatory RCK domains, thus connecting nucleotide binding sites and ion gates. As KtrAB and its homolog TrkAH have been implicated as bacterial pathogenicity factors, the discovery of this functionally relevant inactive conformation may advance structure-guided drug development.

Data availability

The following data sets were generated

1. Diskowski M
2. Mills DJ
3. Baerland N
4. Haenelt I
5. Vonck J
(2016) Structure of the K+ transporter KtrAB from Vibrio alginolyticus in the ADP-bound state
Publicly available at EBI Protein Data Bank (accession no: EMD-3450).

http://www.ebi.ac.uk/pdbe/entry/emdb/EMD-3450

The following previously published data sets were used

(2017) KtrAB potassium transporter from Bacillus subtilis
Publicly available at Protein Data Bank (accession no: 4J7C).

http://www.rcsb.org/pdb/explore/explore.do?structureId=4J7C

Article and author information

Author details

Marina Diskowski

Institute of Biochemistry, Goethe-University, Frankfurt, Germany

Competing interests
The authors declare that no competing interests exist.
Ahmad Reza Mehdipour

Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt, Germany

Competing interests
The authors declare that no competing interests exist.
Dorith Wunnicke

Institute of Biochemistry, Goethe-University, Frankfurt, Germany

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The authors declare that no competing interests exist.
Deryck J Mills

Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt, Germany

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The authors declare that no competing interests exist.
Vedrana Mikusevic

Institute of Biochemistry, Goethe-University, Frankfurt, Germany

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The authors declare that no competing interests exist.
Natalie Bärland

Institute of Biochemistry, Goethe-University, Frankfurt, Germany

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The authors declare that no competing interests exist.
Jan Hoffmann

Institute of Physical and Theoretical Chemistry, Goethe-University, Frankfurt, Germany

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The authors declare that no competing interests exist.
Nina Morgner

Institute of Physical and Theoretical Chemistry, Goethe-University, Frankfurt, Germany

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The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-1872-490X
Heinz-Jürgen Steinhoff

Department of Physics, University of Osnabrück, Osnabrück, Germany

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The authors declare that no competing interests exist.
Gerhard Hummer

Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt, Germany

Competing interests
The authors declare that no competing interests exist.
Janet Vonck

Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt, Germany

For correspondence
janet.vonck@biophys.mpg.de

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0001-5659-8863
Inga Haenelt

Institute of Biochemistry, Goethe-University, Frankfurt, Germany

For correspondence
haenelt@biochem.uni-frankfurt.de

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-1495-3163

Funding

Deutsche Forschungsgemeinschaft (HA 6322/3-1)

Inga Haenelt

Max Planck Society

Ahmad Reza Mehdipour
Deryck J Mills
Gerhard Hummer
Janet Vonck

Deutsche Forschungsgemeinschaft (HA 6322/2-1)

Inga Haenelt

Deutsche Forschungsgemeinschaft (SFB 807)

Nina Morgner
Gerhard Hummer
Inga Haenelt

Deutsche Forschungsgemeinschaft (CEF Macromolecular Complexes)

Ahmad Reza Mehdipour
Inga Haenelt

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.