Biological Assembly 1  

 3D View: Structure

Global Symmetry: Cyclic - C2  (3D View)
Global Stoichiometry: Homo 2-mer - A2 

Biological assembly 1 assigned by authors.

Macromolecule Content

• Total Structure Weight: 30.41 kDa 
• Atom Count: 624 
• Modelled Residue Count: 156 
• Deposited Residue Count: 274 
• Unique protein chains: 1

2I68

Cryo-EM based theoretical model structure of transmembrane domain of the multidrug-resistance antiporter from E. coli EmrE

• DOI: 10.2210/pdb2I68/pdb
• EMDataResource: EMD-1087

• Classification: TRANSPORT PROTEIN
• Organism(s): Escherichia coli
• Expression System: Escherichia coli
• Mutation(s): No 


• Deposited: 2006-08-28 Released: 2006-10-03 
• Deposition Author(s): Fleishman, S.J., Harrington, S.E., Enosh, A., Halperin, D., Tate, C.G., Ben-Tal, N.

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Experimental Data Snapshot

• Method: ELECTRON CRYSTALLOGRAPHY

Literature

Quasi-symmetry in the Cryo-EM Structure of EmrE Provides the Key to Modeling its Transmembrane Domain

Fleishman, S.J., Harrington, S.E., Enosh, A., Halperin, D., Tate, C.G., Ben-Tal, N.

(2006) J Mol Biol 364: 54-67

• PubMed: 17005200 
• DOI: 10.1016/j.jmb.2006.08.072
• Primary Citation of Related Structures:  
  2I68


• PubMed Abstract: 
  

Small multidrug resistance (SMR) transporters contribute to bacterial resistance by coupling the efflux of a wide range of toxic aromatic cations, some of which are commonly used as antibiotics and antiseptics, to proton influx. EmrE is a prototypical small multidrug resistance transporter comprising four transmembrane segments (M1-M4) that forms dimers. It was suggested recently that EmrE molecules in the dimer have different topologies, i.e. monomers have opposite orientations with respect to the membrane plane. A 3-D structure of EmrE acquired by electron cryo-microscopy (cryo-EM) at 7.5 Angstroms resolution in the membrane plane showed that parts of the structure are related by quasi-symmetry. We used this symmetry relationship, combined with sequence conservation data, to assign the transmembrane segments in EmrE to the densities seen in the cryo-EM structure. A C alpha model of the transmembrane region was constructed by considering the evolutionary conservation pattern of each helix. The model is validated by much of the biochemical data on EmrE with most of the positions that were identified as affecting substrate translocation being located around the substrate-binding cavity. A suggested mechanism for proton-coupled substrate translocation in small multidrug resistance antiporters provides a mechanistic rationale to the experimentally observed inverted topology.

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Related Citations: 

• Three-dimensional structure of the bacterial multidrug transporter EmrE shows it is an asymmetric homodimer
  Ubarretxena-Belandia, I., Baldwin, J.M., Schuldiner, S., Tate, C.G.
  (2003) EMBO J 22: 6175

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Organizational Affiliation: 

Department of Biochemistry, George S Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv, Israel.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Protein emrE	A, B	137	Escherichia coli	Mutation(s): 0  Gene Names: emrE, eb, mvrC
Find proteins for P23895 (Escherichia coli (strain K12)) Explore P23895  Go to UniProtKB:  P23895

Experimental Data & Validation

Experimental Data

• Method: ELECTRON CRYSTALLOGRAPHY
• Space Group: P 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 1	α = 90
b = 1	β = 90
c = 1	γ = 90

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2006-08-28 
• Released Date: 2006-10-03 
Deposition Author(s): Fleishman, S.J., Harrington, S.E., Enosh, A., Halperin, D., Tate, C.G., Ben-Tal, N.

Revision History  

• Version 1.0: 2006-10-03
  Type: Initial release
  
• Version 1.1: 2008-05-01
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Version format compliance