The photocycle of orange carotenoid protein conceals distinct intermediates and asynchronous changes in the carotenoid andprotein componentsстатья

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Дата последнего поиска статьи во внешних источниках: 19 декабря 2017 г.

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1. Полный текст MS SR_2017.pdf 4,6 МБ 14 ноября 2017 [emaksimoff]

[1] The photocycle of orange carotenoid protein conceals distinct intermediates and asynchronous changes in the carotenoid andprotein components / E. G. Maksimov, N. N. Sluchanko, Y. B. Slonimskiy et al. // Scientific reports. — 2017. — no. 7. — P. 15548. The 35-kDa Orange Carotenoid Protein (OCP) is responsible for photoprotection in cyanobacteria. It acts as a light intensity sensor and efficient quencher of phycobilisome excitation. Photoactivation triggers large-scale conformational rearrangements to convert OCP from the orange OCPO state to the red active signaling state, OCPR, as demonstrated by various structural methods. Such rearrangements imply a complete, yet reversible separation of structural domains and translocation of the carotenoid. Recently, dynamic crystallography of OCPO suggested the existence of photocycle intermediates with small-scale rearrangements that may trigger further transitions. In this study, we took advantage of single 7 ns laser pulses to study carotenoid absorption transients in OCP on the time-scale from 100 ns to 10 s, which allowed us to detect a red intermediate state preceding the red signaling state, OCPR. In addition, time-resolved fluorescence spectroscopy and the assignment of carotenoid-induced quenching of different tryptophan residues derived thereof revealed a novel orange intermediate state, which appears during the relaxation of photoactivated OCPR to OCPO. Our results show asynchronous changes between the carotenoid- and protein-associated kinetic components in a refined mechanistic model of the OCP photocycle, but also introduce new kinetic signatures for future studies of OCP photoactivity and photoprotection. [ DOI ]

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