| Autor: |
Bühl E; Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt am Main, Max-von-Laue Strasse 7, 60438 Frankfurt, Germany., Resler T; Department of Physics, Experimental Molecular Biophysics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany., Lam R; Max Planck Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt am Main, Germany., Asido M; Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt am Main, Max-von-Laue Strasse 7, 60438 Frankfurt, Germany., Bamberg E; Max Planck Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt am Main, Germany., Schlesinger R; Department of Physics, Genetic Biophysics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany., Bamann C; Max Planck Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt am Main, Germany., Heberle J; Department of Physics, Experimental Molecular Biophysics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany., Wachtveitl J; Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt am Main, Max-von-Laue Strasse 7, 60438 Frankfurt, Germany. |
| Abstrakt: |
The light-gated ion channel channelrhodopsin-2 from Chlamydomonas reinhardtii ( Cr ChR2) is the most frequently used optogenetic tool in neurosciences. However, the precise molecular mechanism of the channel opening and the correlation among retinal isomerization, the photocycle, and the channel activity of the protein are missing. Here, we present electrophysiological and spectroscopic investigations on the R120H variant of Cr ChR2. R120 is a key residue in an extended network linking the retinal chromophore to several gates of the ion channel. We show that despite the deficient channel activity, the photocycle of the variant is intact. In a comparative study for R120H and the wild type, we resolve the vibrational changes in the spectral range of the retinal and amide I bands across the time range from femtoseconds to seconds. Analysis of the amide I mode reveals a significant impairment of the ultrafast protein response after retinal excitation. We conclude that channel opening in Cr ChR2 is prepared immediately after retinal excitation. Additionally, chromophore isomerization is essential for both photocycle and channel activities, although both processes can occur independently. |
