Antiparallel Dimers of the Small Multidrug Resistance Protein EmrE Are More Stable Than Parallel Dimers

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Issue Date
2012-06-14Author
Lloris-Garcerá, Pilar
Bianchi, Frans
Slusky, Joanna
Seppälä, Susanna
Daley, Daniel O.
von Heijne, Gunnar
Publisher
American Society for Biochemistry and Molecular Biology
Type
Article
Article Version
Scholarly/refereed, publisher version
Rights
This research was originally published in Journal of Biological Chemistry. Pilar Lloris-Garcerá, Frans Bianchi, Joanna S. G. Slusky, Susanna Seppälä, Daniel O. Daley and Gunnar von Heijne. Antiparallel Dimers of the Small Multidrug Resistance Protein
EmrE Are More Stable Than Parallel Dimers. Journal of Biological Chemistry. 2012; 287, 26052-26059. © the American Society for Biochemistry and Molecular Biology.
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Show full item recordAbstract
The bacterial multidrug transporter EmrE is a dual-topology membrane protein and as such is able to insert into the membrane in two opposite orientations. The functional form of EmrE is a homodimer; however, the relative orientation of the subunits in the dimer is under debate. Using EmrE variants with fixed, opposite orientations in the membrane, we now show that, although the proteins are able to form parallel dimers, an antiparallel organization of the subunits in the dimer is preferred. Blue-native PAGE analyses of intact oligomers and disulfide cross-linking demonstrate that in membranes, the proteins form parallel dimers only if no oppositely orientated partner is present. Co-expression of oppositely orientated proteins almost exclusively yields antiparallel dimers. Finally, parallel dimers can be disrupted and converted into antiparallel dimers by heating of detergent-solubilized protein. Importantly, in vivo function is correlated clearly to the presence of antiparallel dimers. Our results suggest that an antiparallel arrangement of the subunits in the dimer is more stable than a parallel organization and likely corresponds to the functional form of the protein.
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Citation
Lloris-Garcerá, P., Bianchi, F., Slusky, J. S. G., Seppälä, S., Daley, D. O., & von Heijne, G. (2012). Antiparallel Dimers of the Small Multidrug Resistance Protein EmrE Are More Stable Than Parallel Dimers. The Journal of Biological Chemistry, 287(31), 26052–26059. http://doi.org/10.1074/jbc.M112.357590
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