期刊
JOURNAL OF PHYSICAL CHEMISTRY B
卷 123, 期 15, 页码 3259-3266出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcb.9b01242
关键词
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资金
- Agence Nationale de la Recherche (ANR project CYANOPROTECT) [ANR-11-BSV8-0003]
- Centre National de la Recherche Scientifique (CNRS)
- Commissariat a l'Energie Atomique (CEA)
- Paris-Saclay University (IDI project) [ANR-11-IDEX-0003-02]
- HARVEST EU FP7 Marie Curie Research Training Network
- European Molecular Biology Organization (EMBO)
- Claude Leon Foundation
- University of Pretoria
- French Infrastructure for Integrated Structural Biology (FRISBI) [ANR-10-INSB-05-01]
- Agence Nationale de la Recherche (ANR project RECYFUEL) [ANR-16-CE05-0026]
- Agence Nationale de la Recherche (ANR) [ANR-11-BSV8-0003] Funding Source: Agence Nationale de la Recherche (ANR)
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 Fourier transform infrared (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 alpha-helix domains. At early illumination times, the disappearance of a nonsolvent-exposed alpha-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 a-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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