Activation of a nucleotide-dependent RCK domain requires binding of a cation cofactor to a conserved site

Elife. 2019 Dec 23;8:e50661. doi: 10.7554/eLife.50661.


RCK domains regulate the activity of K+ channels and transporters in eukaryotic and prokaryotic organisms by responding to ions or nucleotides. The mechanisms of RCK activation by Ca2+ in the eukaryotic BK and bacterial MthK K+ channels are well understood. However, the molecular details of activation in nucleotide-dependent RCK domains are not clear. Through a functional and structural analysis of the mechanism of ATP activation in KtrA, a RCK domain from the B. subtilis KtrAB cation channel, we have found that activation by nucleotide requires binding of cations to an intra-dimer interface site in the RCK dimer. In particular, divalent cations are coordinated by the γ-phosphates of bound-ATP, tethering the two subunits and stabilizing the active state conformation. Strikingly, the binding site residues are highly conserved in many different nucleotide-dependent RCK domains, indicating that divalent cations are a general cofactor in the regulatory mechanism of many nucleotide-dependent RCK domains.

Keywords: B. subtilis; KtrAB; RCK domain; molecular biophysics; molecular mechanism; structural biology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / chemistry
  • Bacillus subtilis / chemistry
  • Bacillus subtilis / genetics
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / ultrastructure
  • Binding Sites / genetics
  • Calcium / metabolism
  • Cation Transport Proteins / chemistry*
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / ultrastructure
  • Cations / chemistry
  • Crystallography, X-Ray
  • Kv1.6 Potassium Channel / chemistry
  • Kv1.6 Potassium Channel / ultrastructure
  • Nucleotides / chemistry*
  • Nucleotides / genetics
  • Potassium / chemistry
  • Potassium / metabolism
  • Potassium Channels / chemistry
  • Potassium Channels / genetics
  • Potassium Channels / ultrastructure
  • Protein Conformation*
  • Protein Domains / genetics
  • Protein Structure, Tertiary
  • Ribosomal Proteins


  • Bacterial Proteins
  • Cation Transport Proteins
  • Cations
  • KtrB protein, Bacteria
  • Kv1.6 Potassium Channel
  • Nucleotides
  • Potassium Channels
  • Ribosomal Proteins
  • ribosomal protein BL16
  • Adenosine Triphosphate
  • Potassium
  • Calcium

Associated data

  • PDB/6S2J
  • PDB/6S5B
  • PDB/6S5D
  • PDB/6S7R
  • PDB/6S5N
  • PDB/6S5O
  • PDB/6S5E
  • PDB/6S5G
  • PDB/6S5C
  • PDB/4J90