Engineering the photoactive orange carotenoid protein with redox-controllable structural dynamics and photoprotective function

Publication date: Available online 12 February 2020Source: Biochimica et Biophysica Acta (BBA) - BioenergeticsAuthor(s): Yury B. Slonimskiy, Eugene G. Maksimov, Evgeny P. Lukashev, Marcus Moldenhauer, Thomas Friedrich, Nikolai N. SluchankoAbstractPhotosynthesis requires various photoprotective mechanisms for survival of organisms in high light. In cyanobacteria exposed to high light, the Orange Carotenoid Protein (OCP) is reversibly photoswitched from the orange (OCPO) to the red (OCPR) form, the latter binds to the antenna (phycobilisomes, PBs) and quenches its overexcitation. OCPR accumulation implicates restructuring of a compact dark-adapted OCPO state including detachment of the N-terminal extension (NTE) and separation of protein domains, which is reversed by interaction with the Fluorescence Recovery Protein (FRP). OCP phototransformation supposedly occurs via an intermediate characterized by an OCPR-like absorption spectrum and an OCPO-like protein structure, but the hierarchy of steps remains debatable. Here, we devise and analyze an OCP variant with the NTE trapped on the C-terminal domain (CTD) via an engineered disulfide bridge (OCPCC). NTE trapping preserves OCP photocycling within the compact protein structure but precludes functional interaction with PBs and especially FRP, which is completely restored upon reduction of the disulfide bridge. Non-interacting with the dark-adapted oxidized OCPCC, FRP binds reduced OCPCC nearly as efficiently as OCPO devoid of the...

Source: Biochimica et Biophysica Acta (BBA) Bioenergetics - February 14, 2020 Category: Biochemistry Source Type: research