Comparative ultrafast spectroscopy and structural analysis of OCP1 and OCP2 from Tolypothrix

The orange carotenoid protein (OCP) is a structurally and functionally modular photoactive protein involved in cyanobacterial photoprotection. Recently, based on bioinformatic analysis and phylogenetic relationships, new families of OCP have been described, OCP2 and OCPx. The first characterization...

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Bibliographic Details
Published in:Biochimica et biophysica acta. Bioenergetics 2020-02, Vol.1861 (2)
Main Authors: Kuznetsova, Valentyna, Dominguez-Martin, Maria Agustina, Bao, Han, Gupta, Sayan, Sutter, Markus, Kloz, Miroslav, Rebarz, Mateusz, Přeček, Martin, Chen, Yan, Petzold, Christopher J., Ralston, Corie Y., Kerfeld, Cheryl A., Polívka, Tomáš
Format: Article
Language:English
Subjects:
BASIC BIOLOGICAL SCIENCES
OCP1
OCP2
Photoactivation
Ultrafast spectroscopy
X-ray footprinting
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Summary:The orange carotenoid protein (OCP) is a structurally and functionally modular photoactive protein involved in cyanobacterial photoprotection. Recently, based on bioinformatic analysis and phylogenetic relationships, new families of OCP have been described, OCP2 and OCPx. The first characterization of the OCP2 showed both faster photoconversion and back-conversion, and lower fluorescence quenching of phycobilisomes relative to the well-characterized OCP1. Moreover, OCP2 is not regulated by the fluorescence recovery protein (FRP). In this work, we present a comprehensive study combining ultrafast spectroscopy and structural analysis to compare the photoactivation mechanisms of OCP1 and OCP2 from Tolypothrix PCC 7601. We show that despite significant differences in their functional characteristics, the spectroscopic properties of OCP1 and OCP2 are comparable. This indicates that the OCP functionality is not directly related to the spectroscopic properties of the bound carotenoid. In addition, the structural analysis by X-ray footprinting reveals that, overall, OCP1 and OCP2 have grossly the same photoactivation mechanism. However, the OCP2 is less reactive to radiolytic labeling, suggesting that the protein is less flexible than OCP1. Finally, this observation could explain fast photoconversion of OCP2.
ISSN:0005-2728
1879-2650