Structural basis of proton-coupled potassium transport in the KUP family

Nat Commun. 2020 Jan 31;11(1):626. doi: 10.1038/s41467-020-14441-7.


Potassium homeostasis is vital for all organisms, but is challenging in single-celled organisms like bacteria and yeast and immobile organisms like plants that constantly need to adapt to changing external conditions. KUP transporters facilitate potassium uptake by the co-transport of protons. Here, we uncover the molecular basis for transport in this widely distributed family. We identify the potassium importer KimA from Bacillus subtilis as a member of the KUP family, demonstrate that it functions as a K+/H+ symporter and report a 3.7 Å cryo-EM structure of the KimA homodimer in an inward-occluded, trans-inhibited conformation. By introducing point mutations, we identify key residues for potassium and proton binding, which are conserved among other KUP proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / chemistry
  • Bacillus subtilis / genetics
  • Bacillus subtilis / metabolism*
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Binding Sites
  • Biological Transport
  • Cation Transport Proteins / chemistry*
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism
  • Dimerization
  • Ion Transport
  • Models, Molecular
  • Multigene Family
  • Potassium / metabolism*
  • Protein Domains


  • Bacterial Proteins
  • Cation Transport Proteins
  • Potassium