Reaction dynamics of the chimeric channelrhodopsin C1C2

Yusaku Hontani, Marco Marazzi, Katja Stehfest, Tilo Mathes, Ivo H. M. van Stokkum, Marcus Elstner, Peter Hegemann, John T. M. Kennis

Research output: Contribution to JournalArticleAcademicpeer-review


Channelrhodopsin (ChR) is a key protein of the optogenetic toolkit. C1C2, a functional chimeric protein of Chlamydomonas reinhardtii ChR1 and ChR2, is the only ChR whose crystal structure has been solved, and thus uniquely suitable for structure-based analysis. We report C1C2 photoreaction dynamics with ultrafast transient absorption and multi-pulse spectroscopy combined with target analysis and structure-based hybrid quantum mechanics/molecular mechanics calculations. Two relaxation pathways exist on the excited (S-1) state through two conical intersections Cl-1 and Cl-2, that are reached via clockwise and counter-clockwise rotations: (i) the C13=C14 isomerization path with 450 fs via Cl-1 and (ii) a relaxation path to the initial ground state with 2.0 ps and 11 ps via Cl-2, depending on the hydrogen-bonding network, hence indicating active-site structural heterogeneity. The presence of the additional conical intersection Cl-2 rationalizes the relatively low quantum yield of photoisomerization (30 +/- 3%), reported here. Furthermore, we show the photoreaction dynamics from picoseconds to seconds, characterizing the complete photocycle of C1C2.
Original languageEnglish
Article number7217
JournalScientific Reports
Issue number1
Publication statusPublished - 3 Aug 2017


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