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Related Experiment Videos

Precious things come in little packages.

S Schuldiner1, D Granot, S Steiner

  • 1Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Israel.

Journal of Molecular Microbiology and Biotechnology
|April 26, 2001
PubMed
Summary

The bacterial multidrug transporter EmrE uses a proton gradient to expel drugs. A key glutamate residue (Glu-14) is essential for both substrate binding and proton translocation, forming a shared binding site.

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Area of Science:

  • Molecular Biology
  • Biochemistry
  • Structural Biology

Background:

  • EmrE is a small, hydrophobic multidrug transporter from E. coli.
  • It belongs to the MiniTexan/Smr family and transports various drugs using a proton gradient.
  • EmrE functions as a homo-oligomer and possesses a unique, conserved glutamate residue (Glu-14).

Purpose of the Study:

  • To investigate the structural and functional roles of EmrE, particularly the conserved Glu-14 residue.
  • To elucidate the mechanism of H+/drug antiport and substrate translocation in EmrE.
  • To understand substrate recognition and the coupling mechanism in ion-coupled transporters.

Main Methods:

  • Hydropathic analysis and FTIR spectroscopy to predict and confirm alpha-helical transmembrane segments.

Related Experiment Videos

  • High-resolution heteronuclear NMR and Cysteine scanning experiments to determine protein structure and membrane packing.
  • Site-directed mutagenesis and chemical modification of Glu-14, coupled with pH-dependent binding and transport assays.

    • Main Results:

    • EmrE features four tightly packed alpha-helical transmembrane segments forming a hydrophobic translocation pathway.
    • Glu-14 was identified as a crucial component of the substrate-binding site and is involved in proton binding and translocation.
    • Mutagenesis and chemical modification confirmed Glu-14's role in substrate binding and proton translocation, demonstrating mutually exclusive site occupancy.

    Conclusions:

    • EmrE utilizes a hydrophobic pathway for substrate translocation, facilitated by its unique structural features.
    • Glu-14 is essential for the H+/drug antiport mechanism, acting as a shared binding site for both protons and substrates.
    • EmrE serves as a simple yet powerful model for understanding the fundamental mechanisms of ion-coupled transport and drug efflux pumps.