Biogenesis of a putative channel protein, ComEC, required for DNA uptake: membrane topology, oligomerization and formation of disulphide bonds

Mol Microbiol. 2005 Feb;55(3):881-96. doi: 10.1111/j.1365-2958.2004.04430.x.


ComEC is a putative channel protein for DNA uptake in Bacillus subtilis and other genetically transformable bacteria. Membrane topology studies suggest a model of ComEC as a multispanning membrane protein with seven transmembrane segments (TMSs), and possibly with one laterally inserted amphipathic helix. We show that ComEC contains an intramolecular disulphide bond in its N-terminal extracellular loop (between the residues C131 and C172), which is required for the stability of the protein, and is probably introduced by BdbDC, a pair of competence-induced oxidoreductase proteins. By in vitro cross-linking using native cysteine residues we show that ComEC forms an oligomer. The oligomerization surface includes a transmembrane segment, TMS-G, near the cytoplasmic C-terminus of ComEC.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Bacillus subtilis / genetics
  • Bacillus subtilis / metabolism*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Cell Membrane / chemistry
  • Cell Membrane / metabolism
  • Computer Simulation
  • Cysteine / chemistry
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Dimerization
  • Disulfides / chemistry
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Disulfide Reductase (Glutathione) / metabolism
  • Transformation, Bacterial


  • Bacterial Proteins
  • DNA-Binding Proteins
  • Disulfides
  • Membrane Proteins
  • BdbC protein, Bacillus subtilis
  • BdbD protein, Bacillus subtilis
  • Protein Disulfide Reductase (Glutathione)
  • Cysteine