Characterization of the C-terminal domain of a potassium channel from Streptomyces lividans (KcsA)

J Biol Chem. 2007 Oct 5;282(40):29163-9. doi: 10.1074/jbc.M703277200. Epub 2007 Aug 10.


KcsA, a potassium channel from Streptomyces lividans, is a good model for probing the general working mechanism of potassium channels. To date, the physiological activator of KcsA is still unknown, but in vitro studies showed that it could be opened by lowering the pH of the cytoplasmic compartment to 4. The C-terminal domain (CTD, residues 112-160) was proposed to be the modulator for this pH-responsive event. Here, we support this proposal by examining the pH profiles of: (a) thermal stability of KcsA with and without its CTD and (b) aggregation properties of a recombinant fragment of CTD. We found that the presence of the CTD weakened and enhanced the stability of KcsA at acidic and basic pH values, respectively. In addition, the CTD fragment oligomerized at basic pH values with a transition profile close to that of channel opening. Our results are consistent with the CTD being a pH modulator. We propose herein a mechanism on how this domain may contribute to the pH-dependent opening of KcsA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism*
  • Chymotrypsin / chemistry
  • Cloning, Molecular
  • Cytoplasm / metabolism
  • Escherichia coli / metabolism
  • Hot Temperature
  • Hydrogen-Ion Concentration
  • Ion Channel Gating
  • Molecular Weight
  • Patch-Clamp Techniques
  • Potassium Channels / metabolism*
  • Potassium Chloride / pharmacology
  • Protein Structure, Tertiary
  • Streptomyces lividans / metabolism*
  • Temperature
  • Thrombin / metabolism


  • Bacterial Proteins
  • Potassium Channels
  • prokaryotic potassium channel
  • Potassium Chloride
  • Chymotrypsin
  • Thrombin