Sluchanko Nikolai N, Slonimskiy Yury B, Moldenhauer Marcus, Friedrich Thomas, Maksimov Eugene G
A.N. Bach Institute of Biochemistry, Federal Research Center of Biotechnology of the Russian Academy of Sciences, Moscow, Russia.
Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Russia.
FEBS Lett. 2017 Jun;591(12):1667-1676. doi: 10.1002/1873-3468.12680. Epub 2017 Jun 1.
The orange carotenoid protein (OCP) plays a key role in cyanobacterial photoprotection. Photoconversion entails structural rearrangements in OCP that are required for its binding to phycobilisome, thereby inducing excitation energy dissipation. Detachment of OCP from phycobilisome requires the fluorescence recovery protein (FRP). It is considered that OCP interacts with FRP only in the photoactivated state; however, the binding site for FRP is currently unknown. As an important stabilizing element in orange OCP, the short αA-helix within the N-terminal extension (NTE) binds to the C-terminal domain (CTD), but unfolds upon photoactivation and interferes with phycobilisome binding. Here, we demonstrate that the NTE shares specific structural and functional similarities with FRP and discover the main site of OCP-FRP interactions in the OCP-CTD.
橙色类胡萝卜素蛋白（OCP）在蓝藻的光保护中起关键作用。光转化需要OCP发生结构重排，这是其与藻胆体结合所必需的，从而诱导激发能耗散。OCP从藻胆体上脱离需要荧光恢复蛋白（FRP）。人们认为OCP仅在光激活状态下与FRP相互作用；然而，目前FRP的结合位点尚不清楚。作为橙色OCP中的一个重要稳定元件，N端延伸区（NTE）内的短αA螺旋与C端结构域（CTD）结合，但在光激活时展开并干扰藻胆体结合。在这里，我们证明NTE与FRP具有特定的结构和功能相似性，并发现了OCP-CTD中OCP-FRP相互作用的主要位点。
