Serial femtosecond crystallography reveals that photoactivation in a fluorescent protein proceeds via the hula twist mechanism
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Chromophore cis/trans photoisomerization is a fundamental process in chemistry and in the activation of many photosensitive proteins. A major task is understanding the effect of the protein environment on the efficiency and direction of this reaction compared to what is observed in the gas and solution phases. In this study, we set out to visualize the hula twist (HT) mechanism in a fluorescent protein, which is hypothesized to be the preferred mechanism in a spatially constrained binding pocket. We use a chlorine substituent to break the twofold symmetry of the embedded phenolic group of the chromophore and unambiguously identify the HT primary photoproduct. Through serial femtosecond crystallography, we then track the photoreaction from femtoseconds to the microsecond regime. We observe signals for the photoisomerization of the chromophore as early as 300 fs, obtaining the first experimental structural evidence of the HT mechanism in a protein on its femtosecond-to-picosecond timescale. We are then able to follow how chromophore isomerization and twisting lead to secondary structure rearrangements of the protein β-barrel across the time window of our measurements.
Date Issued
2023-07-26
Date Acceptance
2023-07-01
Citation
Journal of the American Chemical Society, 2023, 145 (29), pp.15796-15808
ISSN
0002-7863
Publisher
American Chemical Society
Start Page
15796
End Page
15808
Journal / Book Title
Journal of the American Chemical Society
Volume
145
Issue
29
Copyright Statement
© 2023 The Authors. Published by American Chemical Society. This work is published under a CC BY licence.
Identifier
https://pubs.acs.org/doi/10.1021/jacs.3c02313
Publication Status
Published
Date Publish Online
2023-07-07