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Updated: Aug 6, 2026

Expression, Detergent Solubilization, and Purification of a Membrane Transporter, the MexB Multidrug Resistance Protein
10:43

Expression, Detergent Solubilization, and Purification of a Membrane Transporter, the MexB Multidrug Resistance Protein

Published on: December 3, 2010

Comparison of three structures of the multidrug transporter EmrE

Christopher G Tate1

  • 1MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK. cgt@mrc-lmb.cam.ac.uk

Current Opinion in Structural Biology
|July 11, 2006
PubMed

Insights

Small multidrug resistance proteins like EmrE confer bacterial resistance via drug efflux. Structural studies reveal EmrE as an asymmetric homodimer, but the biological relevance of observed conformational differences remains uncertain.

Area of Science:

  • Structural biology
  • Biochemistry
  • Microbiology

Background:

  • Small multidrug resistance (SMR) proteins are bacterial antiporters.
  • They confer multidrug resistance through proton-linked drug efflux.
  • EmrE is the archetype of this protein family.

Purpose of the Study:

  • To elucidate the structure of the EmrE protein.
  • To understand the mechanism of multidrug resistance conferred by EmrE.
  • To compare different structural conformations of EmrE.

Main Methods:

  • Electron crystallography was used to determine the structure of EmrE in the membrane.
  • X-ray crystallography was employed to obtain two different EmrE structures.
  • Structural analysis focused on the substrate-binding site and oligomeric state.

Main Results:

  • EmrE forms an asymmetric homodimer in the membrane, with eight alpha helices.
  • Six helices create a substrate-binding site containing tetraphenylphosphonium.
  • Two X-ray structures revealed a non-native tetramer and an asymmetric dimer with bound substrate.

Conclusions:

  • EmrE's structure is an asymmetric homodimer with a defined substrate-binding pocket.
  • Observed conformational differences between structures may not be biologically relevant.
  • Further investigation is needed to clarify EmrE's functional conformational states.

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