Canceled

Joachim Heberle

Freie Universität Berlin, Experimental Molecular Biophysics, Arnimallee 14, 14195 Berlin

Membrane proteins are the target of more than 50% of all drugs and are encoded by about 30% of the human genome. Electrophysiological techniques, like patch-clamp, unravelled many functional aspects of membrane proteins but suffer from structural sensitivity. We have developed Surface Enhanced Infrared Difference Absorption Spectroscopy (SEIDAS) to probe potential-induced structural changes of a protein on the level of a monolayer (see ¹ for a recent review). A novel concept is introduced to incorporate membrane proteins into solid supported lipid bilayers in an orientated manner via the affinity of the His-tag to the Ni-NTA terminated gold surface. General applicability of the methodological approach is shown by tethering photosystem II to the gold surface. In conjunction with hydrogenase, the basis is set towards a biomimetic system for H₂-production. FTIR difference spectra of a monolayer of sensory rhodopsin II were recorded under voltage-clamp conditions. This approach opens an avenue towards mechanistic studies of voltage-gated ion channels with unprecedented structural and temporal sensitivity. Finally, scanning near-field IR micrososcopy will be introduced and applied to study the structure of biomembranes².

Vibrational spectroscopic studies on the novel light-gated channelrhodopsin-2 (ChR2) will be presented. ChR2 represents a versatile tool in the new field of optogenetics where physiological reactions are controlled by light. We have followed the structural changes of ChR2 by static and time-resolved FT-IR spectroscopy and identified internal proton transfer reactions involving aspartate and glutamate residues³. As the resolved protonation changes transiently alter the electrostatics and H-bonding networks within the protein, we infer that they represent the missing mechanistic link between retinal photo-isomerization and channel gating.

References:

1. Ataka, K., Stripp, S., and Heberle, J. Biochim. Biophys. Acta 1828, 2283-93 (2013)
2. Amenabar, I, Poly, S, Nuansing, W, Hubrich, EH, Govyadinov, A, Huth, F, Krutokhvostov, R, Zhang, L, Knez, M, Heberle, J, Bittner, A, Hillenbrand, R. Nature Commun. 2013 Dec 4;4:2890. doi: 10.1038/ncomms3890. (2013)
3. Lórenz-Fonfría, V.A., Resler, T., Krause, N., Nack, M., Gossing, M., Fischer von Mollard, G., Bamann, C., Bamberg, E., Schlesinger, R., and Heberle, J. Proc. Natl. Acad. Sci USA 110 (14), E1273-E1281 (2013)