ISSN 0006-2979, Biochemistry (Moscow), 2017, Vol. 82, No. 13, pp. 1592-1614. © Pleiades Publishing, Ltd., 2017. Original Russian Text © N. N. Sluchanko, Y. B. Slonimskiy, E. G. Maksimov, 2017, published in Uspekhi Biologicheskoi Khimii, 2017, Vol. 57, pp. 71-118. REVIEW Features of Protein-Protein Interactions in the Cyanobacterial Photoprotection Mechanism N. N. Sluchanko1,2*, Y. B. Slonimskiy1,3, and E. G. Maksimov2 1Bach Institute of Biochemistry, Federal Research Center “Fundamentals of Biotechnology”, Russian Academy of Sciences, 119071 Moscow, Russia; E-mail:
[email protected] 2Lomonosov Moscow State University, Faculty of Biology, Biophysics Department, 119991 Moscow, Russia 3Lomonosov Moscow State University, Faculty of Biology, Biochemistry Department, 119991 Moscow, Russia Received August 21, 2017 Revision received September 11, 2017 Abstract—Photoprotective mechanisms of cyanobacteria are characterized by several features associated with the structure of their water-soluble antenna complexes – the phycobilisomes (PBs). During energy transfer from PBs to chlorophyll of photosystem reaction centers, the “energy funnel” principle is realized, which regulates energy flux due to the specialized interaction of the PBs core with a quenching molecule capable of effectively dissipating electron excitation energy into heat. The role of the quencher is performed by ketocarotenoid within the photoactive orange carotenoid protein (OCP), which is also a sensor for light flux. At a high level of insolation, OCP is reversibly photoactivated, and this is accompanied by a sig- nificant change in its structure and spectral characteristics. Such conformational changes open the possibility for pro- tein–protein interactions between OCP and the PBs core (i.e., activation of photoprotection mechanisms) or the fluores- cence recovery protein.