A Unified View on Varied Ultrafast Dynamics of the Primary Process in Microbial Rhodopsins

Chun-Fu Chang; Hikaru Kuramochi; Manish Singh; Rei Abe-Yoshizumi; Tatsuya Tsukuda; Hideki Kandori; Tahei Tahara

doi:10.1002/anie.202111930

A Unified View on Varied Ultrafast Dynamics of the Primary Process in Microbial Rhodopsins

Angew Chem Int Ed Engl. 2022 Jan 10;61(2):e202111930. doi: 10.1002/anie.202111930. Epub 2021 Nov 29.

Authors

Chun-Fu Chang^{1

2}, Hikaru Kuramochi^{1

3

4

5}, Manish Singh⁶, Rei Abe-Yoshizumi⁶, Tatsuya Tsukuda², Hideki Kandori^{6

7}, Tahei Tahara^{1

3}

Affiliations

¹ Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
² Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-0033, Japan.
³ Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
⁴ PRESTO (Japan) Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama, 332-0012, Japan.
⁵ Present address: Research Center of Integrative Molecular Systems, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki, 444-8585, Japan.
⁶ Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-Ku, Nagoya, Aichi, 466-8555, Japan.
⁷ OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-Ku, Nagoya, Aichi, 466-8555, Japan.

PMID: 34670002
DOI: 10.1002/anie.202111930

Abstract

All-trans to 13-cis photoisomerization of the protonated retinal Schiff base (PRSB) chromophore is the primary step that triggers various biological functions of microbial rhodopsins. While this ultrafast primary process has been extensively studied, it has been recognized that the relevant excited-state relaxation dynamics differ significantly from one rhodopsin to another. To elucidate the origin of the complicated ultrafast dynamics of the primary process in microbial rhodopsins, we studied the excited-state dynamics of proteorhodopsin, its D97N mutant, and bacteriorhodopsin by femtosecond time-resolved absorption (TA) spectroscopy in a wide pH range. The TA data showed that their excited-state relaxation dynamics drastically change when pH approaches the pK_a of the counterion residue of the PRSB chromophore in the ground state. This result reveals that the varied excited-state relaxation dynamics in different rhodopsins mainly originate from the difference of the ground-state heterogeneity (i.e., protonation/deprotonation of the PRSB counterion).

Keywords: excited-state dynamics; femtochemistry; microbial rhodopsin; photochemistry.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Rhodopsins, Microbial*

Substances

Rhodopsins, Microbial

Grants and funding

JP25104005/JSPS KAKENHI