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<p>K<sup>+</sup> 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 <i>Vibrio alginolyticus</i>, 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.</p>

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

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年5月7日

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  • Janina Stautz,
  • David Griwatz,
  • Susann Kaltwasser,
  • Ahmad Reza Mehdipour,
  • Sophie Ketter,
  • Celina Thiel,
  • Dorith Wunnicke,
  • Marina Schrecker,
  • Deryck J. Mills,
  • Gerhard Hummer,
  • Janet Vonck,
  • Inga Hänelt

摘要

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.