- EMDB-2859: 3D Reconstruction of Membrane Protein Complex ExbB4-ExbD1-TonB1 -
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Basic information
Entry
Database: EMDB / ID: EMD-2859
Title
3D Reconstruction of Membrane Protein Complex ExbB4-ExbD1-TonB1
Map data
ExbB4-ExbD1-TonB1 complex with extensive dimerization between ExbD and TonB periplasmic domains
Sample
Sample: Membrane protein complex ExbB4-ExbD1-TonB1 from Escherichia coli
Protein or peptide: Biopolymer Transport Protein ExbB
Protein or peptide: Biopolymer Transport Protein ExbD
Protein or peptide: Protein TonB
Keywords
Membrane protein complex / heterodimerization / coordinated rearrangement / iron import
Function / homology
Function and homology information
receptor-mediated bacteriophage irreversible attachment to host cell / colicin transport / ferrichrome import into cell / energy transducer activity / bacteriocin transport / cobalamin transport / siderophore transport / intracellular monoatomic cation homeostasis / cell envelope / plasma membrane protein complex ...receptor-mediated bacteriophage irreversible attachment to host cell / colicin transport / ferrichrome import into cell / energy transducer activity / bacteriocin transport / cobalamin transport / siderophore transport / intracellular monoatomic cation homeostasis / cell envelope / plasma membrane protein complex / protein import / transmembrane transporter complex / transmembrane transporter activity / membrane => GO:0016020 / cell outer membrane / transmembrane transport / protein transport / outer membrane-bounded periplasmic space / intracellular iron ion homeostasis / protein stabilization / protein domain specific binding / protein homodimerization activity / identical protein binding / membrane / plasma membrane Similarity search - Function
: / TonB polyproline region / Gram-negative bacterial TonB protein / : / TonB C-terminal domain profile. / TonB, C-terminal / Gram-negative bacterial TonB protein C-terminal / TonB-system energizer ExbB type-1 / TonB-system energizer ExbB type-1 / TonB/TolA, C-terminal ...: / TonB polyproline region / Gram-negative bacterial TonB protein / : / TonB C-terminal domain profile. / TonB, C-terminal / Gram-negative bacterial TonB protein C-terminal / TonB-system energizer ExbB type-1 / TonB-system energizer ExbB type-1 / TonB/TolA, C-terminal / TonB system transport protein ExbD type-1 / TonB/TolA, C-terminal / TonB system transport protein ExbD type-1 / : / Biopolymer transport protein ExbD/TolR / Biopolymer transport protein ExbD/TolR / MotA/TolQ/ExbB proton channel / MotA/TolQ/ExbB proton channel family Similarity search - Domain/homology
Journal: J Bacteriol / Year: 2015 Title: Membrane Protein Complex ExbB4-ExbD1-TonB1 from Escherichia coli Demonstrates Conformational Plasticity. Authors: Aleksandr Sverzhinsky / Jacqueline W Chung / Justin C Deme / Lucien Fabre / Kristian T Levey / Maria Plesa / David M Carter / Patrick Lypaczewski / James W Coulton / Abstract: Iron acquisition at the outer membrane (OM) of Gram-negative bacteria is powered by the proton motive force (PMF) of the cytoplasmic membrane (CM), harnessed by the CM-embedded complex of ExbB, ExbD, ...Iron acquisition at the outer membrane (OM) of Gram-negative bacteria is powered by the proton motive force (PMF) of the cytoplasmic membrane (CM), harnessed by the CM-embedded complex of ExbB, ExbD, and TonB. Its stoichiometry, ensemble structural features, and mechanism of action are unknown. By panning combinatorial phage libraries, periplasmic regions of dimerization between ExbD and TonB were predicted. Using overexpression of full-length His6-tagged exbB-exbD and S-tagged tonB, we purified detergent-solubilized complexes of ExbB-ExbD-TonB from Escherichia coli. Protein-detergent complexes of ∼230 kDa with a hydrodynamic radius of ∼6.0 nm were similar to previously purified ExbB₄-ExbD₂ complexes. Significantly, they differed in electronegativity by native agarose gel electrophoresis. The stoichiometry was determined to be ExbB₄-ExbD₁-TonB₁. Single-particle electron microscopy agrees with this stoichiometry. Two-dimensional averaging supported the phage display predictions, showing two forms of ExbD-TonB periplasmic heterodimerization: extensive and distal. Three-dimensional (3D) particle classification showed three representative conformations of ExbB₄-ExbD₁-TonB₁. Based on our structural data, we propose a model in which ExbD shuttles a proton across the CM via an ExbB interprotein rearrangement. Proton translocation would be coupled to ExbD-mediated collapse of extended TonB in complex with ligand-loaded receptors in the OM, followed by repositioning of TonB through extensive dimerization with ExbD. Here we present the first report for purification of the ExbB-ExbD-TonB complex, molar ratios within the complex (4:1:1), and structural biology that provides insights into 3D organization. IMPORTANCE: Receptors in the OM of Gram-negative bacteria allow entry of iron-bound siderophores that are necessary for pathogenicity. Numerous iron-acquisition strategies rely upon a ubiquitous and ...IMPORTANCE: Receptors in the OM of Gram-negative bacteria allow entry of iron-bound siderophores that are necessary for pathogenicity. Numerous iron-acquisition strategies rely upon a ubiquitous and unique protein for energization: TonB. Complexed with ExbB and ExbD, the Ton system links the PMF to OM transport. Blocking iron uptake by targeting a vital nanomachine holds promise in therapeutics. Despite much research, the stoichiometry, structural arrangement, and molecular mechanism of the CM-embedded ExbB-ExbD-TonB complex remain unreported. Here we demonstrate in vitro evidence of ExbB₄-ExbD₁-TonB₁ complexes. Using 3D EM, we reconstructed the complex in three conformational states that show variable ExbD-TonB heterodimerization. Our structural observations form the basis of a model for TonB-mediated iron acquisition.
History
Deposition
Jan 22, 2015
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Header (metadata) release
Feb 11, 2015
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Map release
Apr 8, 2015
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Update
May 20, 2015
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Current status
May 20, 2015
Processing site: PDBe / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Entire : Membrane protein complex ExbB4-ExbD1-TonB1 from Escherichia coli
Entire
Name: Membrane protein complex ExbB4-ExbD1-TonB1 from Escherichia coli
Components
Sample: Membrane protein complex ExbB4-ExbD1-TonB1 from Escherichia coli
Protein or peptide: Biopolymer Transport Protein ExbB
Protein or peptide: Biopolymer Transport Protein ExbD
Protein or peptide: Protein TonB
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Supramolecule #1000: Membrane protein complex ExbB4-ExbD1-TonB1 from Escherichia coli
Supramolecule
Name: Membrane protein complex ExbB4-ExbD1-TonB1 from Escherichia coli type: sample / ID: 1000 Oligomeric state: Four ExbB in complex with one ExbD and one TonB Number unique components: 3
Molecular weight
Theoretical: 150 KDa
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Macromolecule #1: Biopolymer Transport Protein ExbB
Macromolecule
Name: Biopolymer Transport Protein ExbB / type: protein_or_peptide / ID: 1 / Name.synonym: ExbB / Number of copies: 4 / Oligomeric state: Tetramer / Recombinant expression: Yes
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