Cryo-EM structures of KdpFABC suggest a K transport mechanism via two inter-subunit half-channels

C Stock, L Hielkema, I Tascón, D Wunnicke, G T Oostergetel, M Azkargorta, C Paulino, I Hänelt

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Abstract

P-type ATPases ubiquitously pump cations across biological membranes to maintain vital ion gradients. Among those, the chimeric K+ uptake system KdpFABC is unique. While ATP hydrolysis is accomplished by the P-type ATPase subunit KdpB, K+ has been assumed to be transported by the channel-like subunit KdpA. A first crystal structure uncovered its overall topology, suggesting such a spatial separation of energizing and transporting units. Here, we report two cryo-EM structures of the 157 kDa, asymmetric KdpFABC complex at 3.7 Å and 4.0 Å resolution in an E1 and an E2 state, respectively. Unexpectedly, the structures suggest a translocation pathway through two half-channels along KdpA and KdpB, uniting the alternating-access mechanism of actively pumping P-type ATPases with the high affinity and selectivity of K+ channels. This way, KdpFABC would function as a true chimeric complex, synergizing the best features of otherwise separately evolved transport mechanisms.

Original languageEnglish
Article number4971
Number of pages10
JournalNature Communications
Volume9
Issue number1
DOIs
Publication statusPublished - 26-Nov-2018

Keywords

  • P-TYPE ATPASE
  • AMINO-ACID SUBSTITUTIONS
  • MEMBRANE REGION M-2C2
  • UPTAKE SYSTEM KTRAB
  • ESCHERICHIA-COLI
  • KDP-ATPASE
  • PHOSPHORYLATION SITE
  • CATION-TRANSPORT
  • ASPARTIC-ACID
  • HIGH-AFFINITY

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