title: Voltage-dependent structural changes of the membrane-bound anion channel hVDAC1 probed by SEIRA and electrochemical impedance spectroscopy.
abstract: The voltage-dependent anion channel (VDAC) is a transmembrane protein that regulates the transfer of metabolites between the cytosol and the mitochondrium. Opening and partial closing of the channel is known to be driven by the transmembrane potential via a mechanism that is not fully understood. In this work, we employed a spectroelectrochemical approach to probe the voltage-induced molecular structure changes of human VDAC1 (hVDAC1) embedded in a tethered bilayer lipid membrane on a nanostructured Au electrode. The model membrane consisted of a mixed self-assembled monolayer of 6-mercaptohexanol and (cholesterylpolyethylenoxy)thiol, followed by the deposition of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine vesicles including hVDAC1. The stepwise assembly of the model membrane and the incorporation of hVDAC1 were monitored by surface enhanced infrared absorption and electrochemical impedance spectroscopy. Difference spectra allowed for identifying the spectral changes which may be associated with the transition from the open to the "closed" states by shifting the potential above or below the transmembrane potential determined to be ca. 0.0 V vs. the open circuit potential. These spectral changes were interpreted on the basis of the orientation- and distance-dependent IR enhancement and indicate alterations of the inclination angle of the β-strands as crucial molecular events, reflecting an expansion or contraction of the β-barrel pore. These protein structural changes that do not confirm nor exclude the reorientation of the α-helix are either directly induced by the electric field or a consequence of a potential-dependent repulsion or attraction of the bilayer.
authors.affiliation: Technische Universität Berlin, Institut für Chemie, Straße des 17. Juni 135, D-10623 Berlin, Germany. hildebrandt@chem.tu-berlin.de kozuch.jacek@mailbox.tu-berlin.de.
authors.forename: Jacek
authors.initials: J
authors.lastname: Kozuch
authors.forename: Conrad
authors.initials: C
authors.lastname: Weichbrodt
authors.forename: Diego
authors.initials: D
authors.lastname: Millo
authors.forename: Karin
authors.initials: K
authors.lastname: Giller
authors.forename: Stefan
authors.initials: S
authors.lastname: Becker
authors.forename: Peter
authors.initials: P
authors.lastname: Hildebrandt
authors.forename: Claudia
authors.initials: C
authors.lastname: Steinem
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D058266:Dielectric Spectroscopy; D004560:Electricity; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D013055:Spectrophotometry, Infrared; D013499:Surface Properties; D050995:Voltage-Dependent Anion Channel 1 / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; C494762:VDAC1 protein, human; D050995:Voltage-Dependent Anion Channel 1