Ultrafast spectroscopy reveals carotenoid configurations in the Orange and Red Carotenoid Proteins from cyanobacteria

Valentyna Kuznetsovaa, Václav Šloufa, Marcel Fucimana, Céline Bourcier de Carbonb,c, Adjélé Wilsonb,c, Diana Kirilovskyb,c, Tomáš Polívkaa,d
a
Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Branišovská 31a, 370 05 České Budějovice, Czech Republic; bInstitute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, 91198 Gif sur Yvette, France; cInstitut de Biologie et Technologies de Saclay (iBiTec-S), Commissariat à l’Energie Atomique (CEA), 91191 Gif-sur-Yvette, France; dInstitute of Plant Molecular Biology, Biological Centre, Czech Academy of Sciences, Branišovská 31, 370 05 České Budějovice, Czech Republic

Excess light energy causes oxidative damage to photosynthetic organisms. One of the photoprotective mechanisms in cyanobacteria involves the Orange Carotenoid Protein (OCP). The OCP structure includes a C-terminal domain, a regulator of the photoprotective activity, and a N-terminal domain, a constitutive quencher [1]. The Red Carotenoid Protein (RCP) represents an isolated activated N-terminal domain of OCP. Recently published X-ray structures of OCP and RCP [2] showed that after photoactivation of OCP the carotenoid translocation within the protein takes place. A femtosecond pump-probe spectroscopic study on OCP binding different carotenoids (echinenone, canthaxanthin, and zeaxanthin) and RCP with canthaxanthin has been performed in our laboratory. The (in)activity of the intramolecular charge-transfer state tracks the changes in carotenoid configurations, and allows to estimate the torsion angles of the end rings. The obtained results together with the X-ray structure enable us to present spectroscopy-structure relationships between OCP and RCP with the carotenoid canthaxanthin. A comparison of OCP binding various carotenoids confirmed that two spectroscopic forms of non-activated OCP coexist, the main and the red form.

References

[1] Leverenz, R.L.; Jallet, D.; Li, M.-D.; Mathies, R.A.; Kirilovsky, D.; Kerfeld, C.A. The Plant Cell 2014, 26, 1–13.
[2] Leverenz, R.L.; Sutter, M.; Wilson, A.; Gupta, S.; Thurotte, A.; Bourcier de Carbon, C.; Petzold, C.J.; Ralston, C.; Perreau, F.; Kirilovsky, D., et al. Science 2015, 348 (6242), 1463–1466.