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Article Dans Une Revue Journal of Physical Chemistry B Année : 2019

Two-Step Structural Changes in Orange Carotenoid Protein Photoactivation Revealed by Time-Resolved Fourier Transform Infrared Spectroscopy

Résumé

The Orange Carotenoid Protein (OCP), which is essential in cyanobacterial photoprotection, is the first photoactive protein containing a carotenoid as an active chromophore. Static and time-resolved FTIR difference spectroscopy under continuous illumination at different temperatures was applied to investigate its photoactivation mechanism. Here we demonstrate that in the OCP, the photo-induced conformational change involves at least two different steps, both in the second timescale at 277 K. Each step involves partial reorganization of α-helix domains. At early illumination times the disappearance of a non-solvent exposed α-helix (negative 1651 cm-1 band) is observed. At longer times, a 1644 cm-1 negative band starts to bleach, showing the disappearance of a solvent-exposed α-helix, either the N-terminal extension and/or the C-terminal tail. A kinetic analysis clearly shows that these two events are asynchronous. Minor modifications in the overall FTIR difference spectra confirm that the global protein conformational change consists of - at least - two asynchronous contributions. Comparison of spectra recorded in H2O and D2O suggests that internal water molecules may contribute to the photoactivation mechanism.
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Dates et versions

hal-02570027 , version 1 (11-05-2020)

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Alberto Mezzetti, Maxime Alexandre, Adrien Thurotte, Adjélé Wilson, Michal Gwizdala, et al.. Two-Step Structural Changes in Orange Carotenoid Protein Photoactivation Revealed by Time-Resolved Fourier Transform Infrared Spectroscopy. Journal of Physical Chemistry B, 2019, 123 (15), pp.3259-3266. ⟨10.1021/acs.jpcb.9b01242⟩. ⟨hal-02570027⟩
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