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12:11
A Rhodopsin Transport Assay by High-Content Imaging Analysis
Published on: January 16, 2019
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Unique Photochemistry Observed in a New Microbial Rhodopsin.
Chihiro Kataoka1, Keiichi Inoue1,2,3,4, Kota Katayama1,2
1Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
The Journal of Physical Chemistry Letters
|August 22, 2019
Summary
Marine bacterial TAT rhodopsin captures light energy via ultrafast photoisomerization. Unlike other rhodopsins, it lacks photointermediates, suggesting a unique photocycle mechanism.
Area of Science:
- Biophysics
- Photochemistry
- Microbial Physiology
Background:
- Animal and microbial rhodopsins capture light energy through ultrafast photoisomerization.
- This process is followed by protein structural changes essential for their functions.
- Understanding rhodopsin photocycles is key to various biological and technological applications.
Purpose of the Study:
- To investigate the early photoreaction mechanism of a marine bacterial TAT rhodopsin.
- To determine if TAT rhodopsin forms photointermediates characteristic of other rhodopsins.
- To elucidate the molecular basis for TAT rhodopsin's unique photochemical behavior.
Main Methods:
- Low-temperature ultraviolet-visible (UV-Vis) spectroscopy.
- Low-temperature Fourier transform infrared (FTIR) spectroscopy.
- Spectroscopic analysis to detect photointermediates and chromophore geometry.
Main Results:
- Marine bacterial TAT rhodopsin exhibits all-trans to 13-cis photoisomerization.
- No photointermediate formation was detected at timescales greater than 10^-5 seconds.
- A planar 13-cis chromophore in the primary K intermediate appears to promote rapid thermal back-isomerization.
Conclusions:
- TAT rhodopsin possesses a distinct early photoreaction pathway compared to other known rhodopsins.
- The planar 13-cis chromophore is a key feature influencing the absence of stable photointermediates.
- This unique mechanism may prevent photocycle completion, suggesting specialized functional adaptations.
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