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Updated: Jul 14, 2026
13:16
Characterization of Membrane Transporters by Heterologous Expression in E. coli and Production of Membrane Vesicles
Published on: December 31, 2019
Conformational changes in a bacterial multidrug transporter are phosphatidylethanolamine-dependent
B Gbaguidi1, P Hakizimana, G Vandenbussche
1Laboratory for Structure and Function of Biological Membranes, Structural Biology and Bioinformatics Center, Free University of Brussels, CP206/2, Bd du Triomphe, Brussels, Belgium.
Cellular and Molecular Life Sciences : CMLS
|May 29, 2007
Summary
Phosphatidylethanolamine (PE) is essential for the antibiotic transporter LmrP to undergo conformational changes. Without PE, LmrP
Area of Science:
- Biochemistry
- Molecular Biology
- Membrane Transport
Background:
- LmrP is an electrogenic H(+)/drug antiporter crucial for extruding diverse antibiotics.
- Specific carboxylic residues (Asp142, Glu327, Asp68, Asp128, Asp235) are implicated in drug binding and proton motive force-driven structural changes.
Purpose of the Study:
- To investigate the role of phosphatidylethanolamine (PE) in LmrP function and conformational changes.
- To determine the ionization behavior and pKa values of LmrP's carboxylic residues in different lipid environments.
Main Methods:
- Attenuated Total Reflection - Fourier Transform Infrared (ATR-FTIR) spectroscopy.
- Tryptophan quenching experiments.
- Reconstitution of LmrP into PE liposomes and lipid-free conditions.
Main Results:
- Phosphatidylethanolamine (PE) is required for the ionization of LmrP's carboxylic residues and the subsequent generation of structural intermediates.
- No ionization-induced conformational changes were observed in the absence of PE.
- The mean pKa of LmrP's carboxylic residues was significantly higher (6.5) in PE liposomes compared to lipid-free conditions (4.6).
Conclusions:
- PE is critical for mediating ionization-dependent conformational changes in LmrP.
- The altered pKa values suggest that extramembrane loop residues interact with the membrane interface, and this interaction is lipid-composition dependent.
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