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Ultrafast Dynamics of Heliorhodopsins
Shinya Tahara1, Manish Singh2, Hikaru Kuramochi3,4,5
1Department of Chemistry, Graduate School of Science , Osaka University , 1-1 Machikaneyama , Toyonaka , Osaka 560-0043 , Japan.
The Journal of Physical Chemistry. B
|February 12, 2019
Summary
Heliorhodopsins, a new rhodopsin family, undergo rapid retinal photoisomerization within femtoseconds. Their ultrafast dynamics resemble type-1 rhodopsins, despite significant sequence differences.
Area of Science:
- Biochemistry
- Photochemistry
- Molecular Biology
Background:
- Heliorhodopsins (HeR) represent a novel rhodopsin family with less than 15% sequence identity to known type-1 and type-2 rhodopsins.
- The distinct amino acid sequences of HeRs prompt investigation into their chromophore photoisomerization mechanism.
Purpose of the Study:
- To investigate the ultrafast photoisomerization dynamics of heliorhodopsins.
- To compare the photochemical properties of HeRs with other rhodopsin families.
Main Methods:
- Femtosecond time-resolved absorption spectroscopy was employed.
- Two HeR variants, HeR 48C12 and an archaeal HeR, were studied.
Main Results:
- Both HeRs displayed excited-state absorption and stimulated emission decaying on a subpicosecond timescale.
- Concomitant appearance of photoproduct absorption confirmed ultrafast retinal photoisomerization in the femtosecond range.
- Transient spectra and dynamics were surprisingly similar to type-1 rhodopsins.
Conclusions:
- Heliorhodopsins exhibit efficient and rapid retinal photoisomerization, a key functional characteristic of rhodopsins.
- Despite sequence divergence, HeRs share functional photochemical similarities with type-1 rhodopsins.
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