Berlin 2015 – scientific programme

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BP: Fachverband Biologische Physik

BP 52: Protein structure and dynamics II

BP 52.7: Talk

Friday, March 20, 2015, 11:30–11:45, H 1028

Dynamics of the Orange Carotenoid Protein (OCP) under Photoactivation — Evgeny Maksimov², •Franz-Josef Schmitt¹, Thomas Friedrich¹, and Vladimir Paschenko² — ¹Institute of Chemistry, Bioenergetics, TU Berlin, Straße des 17. Juni 135, D-10623 Berlin, Germany — ²Department of Biophysics, Biology Faculty, Lomonosov Moscow State University, 119991 Moscow, Russia

The cyanobacterium Synechocystis sp. PCC6803 contains a photoswitchable protein, the orange carotenoid protein (OCP) which undergoes conformational changes under illumination in the blue spectral regime. After activation by light the OCP binds to the membrane extrinsic phycobilisome (PBS) complexes and leads to non-photochemical quenching (NPQ) of the PBS fluorescence reducing the flow of energy into the photosystems under high light conditions as protection mechanism. Time- and wavelength-resolved fluorescence spectroscopy was used to image the dynamics during the photoinduced conformation change and subsequent change in the NPQ efficiency. We suppose that there is a β-ring rotation of the echinenone during photoactivation of OCP that leads to a significant red shift of the absorption spectrum. A distance change between Tyr-201, Trp-288 and the keto terminus of the pigment might break H-bonds between the protein and the chromophore which tilt the β-ring out of plane in the inactive form of OCP.