PMID:10637227
| Citation |
Muth, TR and Schuldiner, S (2000) A membrane-embedded glutamate is required for ligand binding to the multidrug transporter EmrE. EMBO J. 19:234-40 |
|---|---|
| Abstract |
EmrE is an Escherichia coli multidrug transporter that confers resistance to a variety of toxins by removing them in exchange for hydrogen ions. The detergent-solubilized protein binds tetraphenylphosphonium (TPP(+)) with a K(D) of 10 nM. One mole of ligand is bound per approximately 3 mol of EmrE, suggesting that there is one binding site per trimer. The steep pH dependence of binding suggests that one or more residues, with an apparent pK of approximately 7.5, release protons prior to ligand binding. A conservative Asp replacement (E14D) at position 14 of the only membrane-embedded charged residue shows little transport activity, but binds TPP(+) at levels similar to those of the wild-type protein. The apparent pK of the Asp shifts to <5.0. The data are consistent with a mechanism requiring Glu14 for both substrate and proton recognition. We propose a model in which two of the three Glu14s in the postulated trimeric EmrE homooligomer deprotonate upon ligand binding. The ligand is released on the other face of the membrane after binding of protons to Glu14. |
| Links |
PubMed PMC305557 Online version:10.1093/emboj/19.2.234 |
| Keywords |
Amino Acid Sequence; Antiporters; Aspartic Acid; Bacterial Proteins/chemistry; Bacterial Proteins/metabolism; Binding Sites; Biological Transport; Carrier Proteins/chemistry; Carrier Proteins/metabolism; Cell Membrane/metabolism; Cell Membrane/ultrastructure; Conserved Sequence; Escherichia coli/metabolism; Escherichia coli Proteins; Glutamic Acid; Hydrogen-Ion Concentration; Indicators and Reagents; Kinetics; Membrane Proteins/chemistry; Membrane Proteins/metabolism; Molecular Sequence Data; Onium Compounds/metabolism; Organophosphorus Compounds/metabolism; Recombinant Proteins/chemistry; Recombinant Proteins/metabolism |
| edit table |
Significance
You can help EcoliWiki by summarizing why this paper is useful
Useful Materials and Methods
You can help Ecoliwiki by describing the useful materials (strains, plasmids, antibodies, etc) described in this paper.
Annotations
<annotationlinks/>
EcoliWiki Links
Add links to pages that link here (e.g. gene, product, method pages)
References
See Help:References for how to manage references in EcoliWiki.