Distinct gate conformations of the ABC transporter BtuCD revealed by electron spin resonance spectroscopy and chemical cross-linking

FEBS Lett. 2009 Jan 22;583(2):266-70. doi: 10.1016/j.febslet.2008.12.020. Epub 2008 Dec 25.


BtuCD is a type II ABC importer that catalyzes the translocation of vitamin B12 from the periplasm into the cytoplasm of Escherichia coli. Crystal structures of BtuCD and the related HiF (or Hi1470/71) protein from Haemophilus influenzae have revealed distinct conformations of the transmembrane domains that form inner and outer gates. We used electron spin resonance spectroscopy to study the reaction cycle of BtuCD after labeling the protein at residues located at these gates. The results suggest that BtuCD as a prototype type II ABC importer may have a mechanism that is distinct from that of ABC exporters such as Sav1866 or type I ABC importers such as those specific for molybdate (ModBC) or maltose (MalFGK).

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry*
  • ATP-Binding Cassette Transporters / genetics
  • Cross-Linking Reagents / chemistry
  • Electron Spin Resonance Spectroscopy
  • Haemophilus influenzae / metabolism*
  • Protein Conformation


  • ATP-Binding Cassette Transporters
  • Cross-Linking Reagents