Dual photoisomerization on distinct potential energy surfaces in a UV-absorbing rhodopsin

0536453 - FZÚ 2021 RIV US eng J - Článek v odborném periodiku
Hontani, Y. - Broser, M. - Luck, M. - Weissenborn, J. - Kloz, Miroslav - Hegemann, P. - Kennis, J.T.M.
Dual photoisomerization on distinct potential energy surfaces in a UV-absorbing rhodopsin.
Journal of the American Chemical Society. Roč. 142, č. 26 (2020), s. 11464-11473. ISSN 0002-7863. E-ISSN 1520-5126
Institucionální podpora: RVO:68378271
Klíčová slova: resolution optical spectroscopy * stretching Raman lines * all-trans * resonance raman * electronic excitations * ultraviolet vision * Schiff-bases * femtosecond
Obor OECD: Biophysics
Impakt faktor: 15.419, rok: 2020
Způsob publikování: Open access

UV-absorbing rhodopsins are essential for UV vision and sensing in all kingdoms of life. Unlike the well-known visible-absorbing rhodopsins, which bind a protonated retinal Schiff base for light absorption, UV-absorbing rhodopsins bind an unprotonated retinal Schiff base. Thus far, the photoreaction dynamics and mechanisms of UV-absorbing rhodopsins have remained essentially unknown. Here, we report the complete excited- and ground-state dynamics of the UV form of histidine kinase rhodopsin 1 (HKR1) from eukaryotic algae, using femtosecond stimulated Raman spectroscopy (FSRS) and transient absorption spectroscopy, covering time scales from femtoseconds to milliseconds. We found that energy-level ordering is inverted with respect to visible-absorbing rhodopsins, with an optically forbidden low-lying S-1 excited state that has Ag- symmetry and a higher-lying UV-absorbing S-2 state of Bu+ symmetry. UV-photoexcitation to the S-2 state elicits a unique dual-isomerization reaction: first, C13=C14 cis-trans isomerization occurs during S-2-S-1 evolution in <100 fs. This very fast reaction features the remarkable property that the newly formed isomer appears in the excited state rather than in the ground state. Second, C15=N16 anti-syn isomerization occurs on the S-1-S-0 evolution to the ground state in 4.8 ps. We detected two ground-state unprotonated retinal photoproducts, 13-trans/15-anti (all-trans) and 13-cis/15-syn, after relaxation to the ground state. These isomers become protonated in 58 mu s and 3.2 ms, respectively, resulting in formation of the blue-absorbing form of HKR1. Our results constitute a benchmark of UV-induced photochemistry of animal and microbial rhodopsins.
Trvalý link: http://hdl.handle.net/11104/0314228