Probing the structure of the dimeric KtrB membrane protein

J Biol Chem. 2007 Nov 30;282(48):35046-55. doi: 10.1074/jbc.M704260200. Epub 2007 Oct 10.


The KtrAB ion transporter is a complex of two proteins, KtrB and KtrA. The integral membrane protein KtrB is expected to adopt the structural architecture typified by the pore domain of potassium channels. Here we show that homo-dimerization of KtrB proteins is most likely a general property of this family of transporters. Using cysteine mutants and bifunctional cross-linkers we define regions of the Bacillus subtilis KtrB molecule that are close to the molecular 2-fold axis and to the dimer interface. Fitting of the cross-linking data to a potassium channel-like model suggests structural similarities between potassium channels and KtrB proteins in the extracellular half of the molecule and differences in the cytoplasmic regions.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacillus / metabolism
  • Bacillus subtilis / metabolism*
  • Bacterial Proteins / metabolism*
  • Cation Transport Proteins / metabolism*
  • Cross-Linking Reagents / pharmacology
  • Cysteine / chemistry
  • Cytoplasm / metabolism
  • Dimerization
  • Molecular Conformation
  • Molecular Sequence Data
  • Mutation
  • Potassium / chemistry
  • Potassium Channels / chemistry
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid
  • Streptococcus pneumoniae / metabolism


  • Bacterial Proteins
  • Cation Transport Proteins
  • Cross-Linking Reagents
  • KtrB protein, Bacteria
  • Potassium Channels
  • Cysteine
  • Potassium