The multidrug resistance efflux complex, EmrAB from Escherichia coli forms a dimer in vitro

Mikio Tanabe, Gerda Szakonyi, Katherine A. Brown, Peter J.F. Henderson, Jon Nield, Bernadette Byrne

Research output: Contribution to journalArticle

36 Citations (Scopus)


Tripartite efflux systems are responsible for the export of toxins across both the inner and outer membranes of Gram negative bacteria. Previous work has indicated that EmrAB-TolC from Escherichia coli is such a tripartite system, comprised of EmrB an MFS transporter, EmrA, a membrane fusion protein and TolC, an outer membrane channel. The whole complex is predicted to form a continuous channel allowing direct export from the cytoplasm to the exterior of the cell. Little is known, however, about the interactions between the individual components of this system. Reconstitution of EmrA + EmrB resulted in co-elution of the two proteins from a gel filtration column indicating formation of the EmrAB complex. Electron microscopic single particle analysis of the reconstituted EmrAB complex revealed the presence of particles approximately 240 × 140 Å, likely to correspond to two EmrAB dimers in a back-to-back arrangement, suggesting the dimeric EmrAB form is the physiological state contrasting with the trimeric arrangement of the AcrAB-TolC system.

Original languageEnglish
Pages (from-to)338-342
Number of pages5
JournalBiochemical and biophysical research communications
Issue number2
Publication statusPublished - Mar 6 2009


  • EmrAB-TolC
  • Membrane transport
  • Multidrug resistance
  • Oligomer
  • Single particle electron microscopy
  • Tripartite efflux system

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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