Multidrug-exporting secondary transporters

Curr Opin Struct Biol. 2003 Aug;13(4):443-52. doi: 10.1016/s0959-440x(03)00109-x.


The major cause of intrinsic drug resistance in Gram-negative bacteria is a resistance nodulation division type multidrug exporter, which couples with an outer membrane channel and a membrane fusion protein and exports drugs out of the cell, bypassing the periplasm; this process is driven by proton motive force. A recent crystal structure determination of a major resistance nodulation division type multidrug exporter, AcrB in Escherichia coli, greatly advances our understanding of the multidrug export mechanism. The most striking feature of the AcrB trimer is the presence of three vestibules open to the periplasm at the boundary between the periplasmic headpiece and the transmembrane region. Substrates can gain access to the central cavity from the periplasmic surface of the cytoplasmic membrane and are then actively transported through the extramembrane pore into the outer membrane channel TolC, via the funnel at the top of the AcrB headpiece.

Publication types

  • Review

MeSH terms

  • Bacterial Outer Membrane Proteins / physiology
  • Biological Transport, Active / physiology
  • Carrier Proteins / genetics
  • Carrier Proteins / physiology*
  • Drug Resistance, Multiple / genetics
  • Drug Resistance, Multiple / physiology*
  • Escherichia coli / genetics
  • Escherichia coli / physiology
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / physiology*
  • Membrane Proteins / genetics
  • Membrane Proteins / physiology*
  • Membrane Transport Proteins
  • Multidrug Resistance-Associated Proteins
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary


  • AcrB protein, E coli
  • Bacterial Outer Membrane Proteins
  • Carrier Proteins
  • Escherichia coli Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Multidrug Resistance-Associated Proteins
  • tolC protein, E coli