Journal Article

PreJuSER-588

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Resolving voltage-dependent structural changes of a membrane photoreceptor by surface-enhanced IR difference spectroscopy

Jiang, X. ; Zaitseva, E. ; Schmidt, M. ; Siebert, F. ; Engelhard, M. ; Schlesinger, R.FZJ* ; Ataka, K. ; Vogel, R. ; Heberle, J.

2008
Academy Washington, DC

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Please use a persistent id in citations: doi:10.1073/pnas.0802289105

Abstract: Membrane proteins are molecular machines that transport ions, solutes, or information across the cell membrane. Electrophysiological techniques have unraveled many functional aspects of ion channels but suffer from the lack of structural sensitivity. Here, we present spectroelectrochemical data on vibrational changes of membrane proteins derived from a single monolayer. For the seven-helical transmembrane protein sensory rhodopsin II, structural changes of the protein backbone and the retinal cofactor as well as single ion transfer events are resolved by surface-enhanced IR difference absorption spectroscopy (SEIDAS). Angular changes of bonds versus the membrane normal have been determined because SEIDAS monitors only those vibrations whose dipole moment are oriented perpendicular to the solid surface. The application of negative membrane potentials (DeltaV = -0.3 V) leads to the selective halt of the light-induced proton transfer at the stage of D75, the counter ion of the retinal Schiff base. It is inferred that the voltage raises the energy barrier of this particular proton-transfer reaction, rendering the energy deposited in the retinal by light excitation insufficient for charge transfer to occur. The other structural rearrangements that accompany light-induced activity of the membrane protein, are essentially unaffected by the transmembrane electric field. Our results demonstrate that SEIDAS is a generic approach to study processes that depend on the membrane potential, like those in voltage-gated ion channels and transporters, to elucidate the mechanism of ion transfer with unprecedented spatial sensitivity and temporal resolution.

Keyword(s): Ion Channel Gating (MeSH) ; Light (MeSH) ; Membrane Potentials (MeSH) ; Membrane Proteins: chemistry (MeSH) ; Photoreceptor Cells: chemistry (MeSH) ; Protein Conformation (MeSH) ; Rhodopsin: chemistry (MeSH) ; Spectrophotometry, Infrared: methods (MeSH) ; Membrane Proteins ; Rhodopsin ; J ; ion transfer (auto) ; membrane potential (auto) ; proton translocation (auto) ; vibrational spectroscopy (auto) ; sensory rhodopsin (auto)

Note: We thank Rebecca M. Nyquist for reading the manuscript; R.S. thanks Georg Buldt for generous support; and J.H. acknowledges helpful discussions with Eberhard Neumann and Benjamin Kaupp. This work was supported by grants from the German Ministry for Science and Education (to J.H.) and Deutsche Forschungsgemeinschaft Grant Vo 811/3,4 (to R.V.) and Za 566/1-1 (to E.Z.). X.J. thanks the Alexander-von-Humboldt foundation for a fellowship.

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Contributing Institute(s):

1. Molekulare Biophysik (INB-2)

Research Program(s):

1. Funktion und Dysfunktion des Nervensystems (P33)

Appears in the scientific report 2008

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