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

Alberto Mezzetti*, Maxime Alexandre, Adrien Thurotte, Adjelé Wilson, Michal Gwizdala, Diana Kirilovsky

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

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 α-helix domains. At early illumination times, the disappearance of a nonsolvent-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 H 2 O and D 2 O suggests that internal water molecules may contribute to the photoactivation mechanism.

Original languageEnglish
Pages (from-to)3259-3266
Number of pages8
JournalJournal of Physical Chemistry B
Volume123
Issue number15
Early online date21 Mar 2019
DOIs
Publication statusPublished - 18 Apr 2019

Fingerprint

Dive into the research topics of 'Two-Step Structural Changes in Orange Carotenoid Protein Photoactivation Revealed by Time-Resolved Fourier Transform Infrared Spectroscopy'. Together they form a unique fingerprint.

Cite this