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Structural basis for potassium transport in prokaryotes by KdpFABC

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DOI

  • Marie E. Sweet, New York University
  • ,
  • Casper Larsen
  • ,
  • Xihui Zhang, New York University
  • ,
  • Michael Schlame, New York University
  • ,
  • Bjørn P. Pedersen
  • David L. Stokes, New York University

KdpFABC is an oligomeric K+ transport complex in prokaryotes that maintains ionic homeostasis under stress conditions. The complex comprises a channel-like subunit (KdpA) from the superfamily of K+ transporters and a pump-like subunit (KdpB) from the superfamily of P-type ATPases. Recent structural work has defined the architecture and generated contradictory hypotheses for the transport mechanism. Here, we use substrate analogs to stabilize four key intermediates in the reaction cycle and determine the corresponding structures by cryogenic electron microscopy. We find that KdpB undergoes conformational changes consistent with other representatives from the P-type superfamily, whereas KdpA, KdpC, and KdpF remain static. We observe a series of spherical densities that we assign as K+ or water and which define a pathway for K+ transport. This pathway runs through an intramembrane tunnel in KdpA and delivers ions to sites in the membrane domain of KdpB. Our structures suggest a mechanism where ATP hydrolysis is coupled to K+ transfer between alternative sites in KdpB, ultimately reaching a low-affinity site where a water-filled pathway allows release of K+ to the cytoplasm.

Original languageEnglish
Article numbere2105195118
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue29
ISSN0027-8424
DOIs
Publication statusPublished - Jul 2021

Bibliographical note

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© 2021 National Academy of Sciences. All rights reserved.

    Research areas

  • Membrane transport | P-type ATPase energy coupling | stress response

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