A short intrinsically disordered region at KtrB’s N-terminus facilitates allosteric regulation of K+ channel KtrAB

Janina Stautz, David Griwatz, Susann Kaltwasser, Ahmad Reza Mehdipour, Sophie Ketter, Celina Thiel, Dorith Wunnicke, Marina Schrecker, Deryck J. Mills, Gerhard Hummer, Janet Vonck () and Inga Hänelt ()
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Janina Stautz: Goethe University Frankfurt
David Griwatz: Goethe University Frankfurt
Susann Kaltwasser: Max Planck Institute of Biophysics
Ahmad Reza Mehdipour: Ghent University
Sophie Ketter: Goethe University Frankfurt
Celina Thiel: Goethe University Frankfurt
Dorith Wunnicke: Goethe University Frankfurt
Marina Schrecker: Goethe University Frankfurt
Deryck J. Mills: Max Planck Institute of Biophysics
Gerhard Hummer: Max Planck Institute of Biophysics
Janet Vonck: Max Planck Institute of Biophysics
Inga Hänelt: Goethe University Frankfurt

Nature Communications, 2025, vol. 16, issue 1, 1-16

Abstract: Abstract K+ homeostasis is crucial for bacterial survival. The bacterial K+ channel KtrAB is regulated by the binding of ADP and ATP to the cytosolic RCK subunits KtrA. While the ligand-induced conformational changes in KtrA are well described, the transmission to the gating regions within KtrB is not understood. Here, we present a cryo-EM structure of the ADP-bound, inactive KtrAB complex from Vibrio alginolyticus, which resolves part of KtrB’s N termini. They are short intrinsically disordered regions (IDRs) located at the interface of KtrA and KtrB. We reveal that these IDRs play a decisive role in ATP-mediated channel opening, while the closed ADP-bound state does not depend on the N-termini. We propose an allosteric mechanism, in which ATP-induced conformational changes within KtrA trigger an interaction of KtrB’s N-terminal IDRs with the membrane, stabilizing the active and conductive state of KtrAB.

Date: 2025
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DOI: 10.1038/s41467-025-59546-z

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