| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1944215 | Biochimica et Biophysica Acta (BBA) - Biomembranes | 2014 | 6 Pages |
•For the first time we report the 2D monomer–dimer equilibrium constant of EmrE.•EmrE dimer is more stable in lipid bilayer than in bicelles.•EmrE dimer is much more stable in bicelles than detergent micelles.•Substrate not involved in EmrE dimer stability.
The small multi-drug resistant (SMR) transporter EmrE functions as a homodimer. Although the small size of EmrE would seem to make it an ideal model system, it can also make it challenging to work with. As a result, a great deal of controversy has surrounded even such basic questions as the oligomeric state. Here we show that the purified protein is a homodimer in isotropic bicelles with a monomer–dimer equilibrium constant (KMD2D) of 0.002–0.009 mol% for both the substrate-free and substrate-bound states. Thus, the dimer is stabilized in bicelles relative to detergent micelles where the KMD2D is only 0.8–0.95 mol% (Butler et al. 2004). In dilauroylphosphatidylcholine (DLPC) liposomes KMD2D is 0.0005–0.0008 mol% based on Förster resonance energy transfer (FRET) measurements, slightly tighter than bicelles. These results emphasize the importance of the lipid membrane in influencing dimer affinity.
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