scholarly journals Lipid Composition Regulates the Orientation of Transmembrane Helices in HorA, an ABC Multidrug Transporter

2010 ◽  
Vol 285 (19) ◽  
pp. 14144-14151 ◽  
Author(s):  
Adelin Gustot ◽  
Smriti ◽  
Jean-Marie Ruysschaert ◽  
Hassane Mchaourab ◽  
Cédric Govaerts
Keyword(s):  
Lipid Composition ◽  
Multidrug Transporter ◽  
Transmembrane Helices

The Reconstitution and Activity of the Small Multidrug Transporter EmrE is Modulated by Non-bilayer Lipid Composition

2004 ◽  
Vol 343 (1) ◽  
pp. 213-222 ◽  
Author(s):  
Paul Curnow ◽  
Mark Lorch ◽  
Kalypso Charalambous ◽  
Paula J. Booth
Keyword(s):  
Lipid Composition ◽  
Multidrug Transporter ◽  
Bilayer Lipid

scholarly journals Energetics and Conformational Pathways of Functional Rotation in the Multidrug Transporter AcrB

2017 ◽  
Author(s):  
Yasuhiro Matsunaga ◽  
Tsutomu Yamane ◽  
Tohru Terada ◽  
Kei Moritsugu ◽  
Hiroshi Fujisaki ◽  
...  
Keyword(s):  
Free Energy ◽  
Drug Transport ◽  
Proton Translocation ◽  
Minimum Free Energy ◽  
Proton Motive Force ◽  
Free Energy Calculations ◽  
Vertical Shear ◽  
Multidrug Transporter ◽  
Simulation Studies ◽  
Transmembrane Helices

The multidrug transporter AcrB transports a broad range of drugs out of the cell by means of the proton-motive force. The asymmetric crystal structure of trimeric AcrB suggests a functionally rotating mechanism for drug transport. Despite various supportive evidences from biochemical and simulation studies for this mechanism, the link between the functional rotation and proton translocation across the membrane remains elusive. Here, calculating the minimum free energy pathway of the functional rotation for the complete AcrB trimer, we describe the structural and energetic basis behind the coupling between the functional rotation and the proton translocation at atomic-level. Free energy calculations show that protonation of Asp408 in the transmembrane portion of the drug-bound protomer drives the functional rotation. The conformational pathway identifies vertical shear motions among several transmembrane helices, which regulates alternate access of water in the transmembrane as well as peristaltic motions pumping drugs in the periplasm.

scholarly journals EmrE, the smallest ion-coupled transporter, provides a unique paradigm for structure-function studies.

1997 ◽  
Vol 200 (2) ◽  
pp. 335-341
Author(s):  
S Schuldiner ◽  
M Lebendiker ◽  
H Yerushalmi
Keyword(s):  
Functional Form ◽  
Amide Proton ◽  
Multidrug Transporter ◽  
Hydrogen Ions ◽  
Transmembrane Helices ◽  
Wild Type ◽  
Infrared Measurements ◽  
Highly Hydrophobic ◽  
Negative Dominance ◽  
Hydrophobicity Analysis

EmrE is an Escherichia coli multidrug transporter which confers resistance to a wide variety of toxicants by actively removing them in exchange for hydrogen ions. EmrE is a highly hydrophobic 12 kDa protein which has been purified by taking advantage of its unique solubility in organic solvents. After solubilization and purification, the protein retains its ability to transport as judged from the fact that it can be reconstituted in a functional form. Hydrophobicity analysis of the sequence yielded four putative transmembrane domains of similar sizes. Results from transmission Fourier transform infrared measurements agree remarkably well with this hypothesis and yielded alpha-helical estimates of 78% and 80% for EmrE in CHCl3:MeOH and 1,2-dimyristoyl phosphocholine, respectively. Furthermore, the fact that most of the amide groups in the protein do not undergo amide-proton H/D exchange implies that most (approximately 80%) of the residues are embedded in the bilayer. These observations are only consistent with four transmembrane helices. A domain lined by Cys41 and Cys95 accessible only to substrates such as the organic mercurial 4-(chloromercuri)benzoic acid has been identified. Both residues are asymmetric in their location with respect to the plane of the membrane, Cys95 being closer than Cys41 to the outside face of the membrane. In co-reconstitution experiments of wild-type protein with three different inactive mutants, negative dominance has been observed. This phenomenon suggests that EmrE is functional as a homo-oligomer.

scholarly journals Protonation-dependent conformational dynamics of the multidrug transporter EmrE

2016 ◽  
Vol 113 (5) ◽  
pp. 1220-1225 ◽  
Author(s):  
Reza Dastvan ◽  
Axel W. Fischer ◽  
Smriti Mishra ◽  
Jens Meiler ◽  
Hassane S. Mchaourab
Keyword(s):  
Conformational Changes ◽  
Transport Model ◽  
Conformational Dynamics ◽  
Bound State ◽  
Multidrug Transporter ◽  
Transmembrane Helices ◽  
Transport Cycle ◽  
Double Electron ◽  
Double Electron Electron Resonance ◽  
Alternating Access

The small multidrug transporter from Escherichia coli, EmrE, couples the energetically uphill extrusion of hydrophobic cations out of the cell to the transport of two protons down their electrochemical gradient. Although principal mechanistic elements of proton/substrate antiport have been described, the structural record is limited to the conformation of the substrate-bound state, which has been shown to undergo isoenergetic alternating access. A central but missing link in the structure/mechanism relationship is a description of the proton-bound state, which is an obligatory intermediate in the transport cycle. Here we report a systematic spin labeling and double electron electron resonance (DEER) study that uncovers the conformational changes of EmrE subsequent to protonation of critical acidic residues in the context of a global description of ligand-induced structural rearrangements. We find that protonation of E14 leads to extensive rotation and tilt of transmembrane helices 1–3 in conjunction with repacking of loops, conformational changes that alter the coordination of the bound substrate and modulate its access to the binding site from the lipid bilayer. The transport model that emerges from our data posits a proton-bound, but occluded, resting state. Substrate binding from the inner leaflet of the bilayer releases the protons and triggers alternating access between inward- and outward-facing conformations of the substrate-loaded transporter, thus enabling antiport without dissipation of the proton gradient.

scholarly journals Energetics and conformational pathways of functional rotation in the multidrug transporter AcrB

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Yasuhiro Matsunaga ◽  
Tsutomu Yamane ◽  
Tohru Terada ◽  
Kei Moritsugu ◽  
Hiroshi Fujisaki ◽  
...  
Keyword(s):  
Free Energy ◽  
Drug Transport ◽  
Proton Translocation ◽  
Minimum Free Energy ◽  
Proton Motive Force ◽  
Free Energy Calculations ◽  
Vertical Shear ◽  
Multidrug Transporter ◽  
Simulation Studies ◽  
Transmembrane Helices

The multidrug transporter AcrB transports a broad range of drugs out of the cell by means of the proton-motive force. The asymmetric crystal structure of trimeric AcrB suggests a functionally rotating mechanism for drug transport. Despite various supportive forms of evidence from biochemical and simulation studies for this mechanism, the link between the functional rotation and proton translocation across the membrane remains elusive. Here, calculating the minimum free energy pathway of the functional rotation for the complete AcrB trimer, we describe the structural and energetic basis behind the coupling between the functional rotation and the proton translocation at atomic resolution. Free energy calculations show that protonation of Asp408 in the transmembrane portion of the drug-bound protomer drives the functional rotation. The conformational pathway identifies vertical shear motions among several transmembrane helices, which regulate alternate access of water in the transmembrane as well as peristaltic motions that pump drugs in the periplasm.

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