Structure of the periplasmic adaptor protein from a major facilitator superfamily (MFS) multidrug efflux pump

FEBS Lett. 2014 Aug 25;588(17):3147-53. doi: 10.1016/j.febslet.2014.06.055. Epub 2014 Jul 1.


Periplasmic adaptor proteins are key components of bacterial tripartite efflux pumps. The 2.85 Å resolution structure of an MFS (major facilitator superfamily) pump adaptor, Aquifex aeolicus EmrA, shows linearly arranged α-helical coiled-coil, lipoyl, and β-barrel domains, but lacks the fourth membrane-proximal domain shown in other pumps to interact with the inner membrane transporter. The adaptor α-hairpin, which binds outer membrane TolC, is exceptionally long at 127 Å, and the β-barrel contains a conserved disordered loop. The structure extends the view of adaptors as flexible, modular components that mediate diverse pump assembly, and suggests that in MFS tripartite pumps a hexamer of adaptors could provide a periplasmic seal.

Keywords: Adaptor protein; Antibiotic resistance; Crystal structure; Major facilitator superfamily; Multidrug efflux.

MeSH terms

  • Amino Acid Sequence
  • Aquifoliaceae
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Conserved Sequence
  • Crystallography, X-Ray
  • Ligands
  • Membrane Transport Proteins / chemistry*
  • Membrane Transport Proteins / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Structure, Secondary
  • Protein Structure, Tertiary


  • Bacterial Proteins
  • Ligands
  • Membrane Transport Proteins