Stages of OCP–FRP Interactions in the Regulation of Photoprotection in Cyanobacteria, Part 2: Small-Angle Neutron Scattering with Partial Deuteration

We used small-angle neutron scattering partially coupled with size-exclusion chromatography to unravel the solution structures of two variants of the Orange Carotenoid Protein (OCP) lacking the N-terminal extension (OCP-ΔNTE) and its complex formation with the Fluorescence Recovery Protein (FRP). Th...

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Published in:The journal of physical chemistry. B 2023-03, Vol.127 (9), p.1901-1913
Main Authors: Golub, Maksym, Moldenhauer, Marcus, Matsarskaia, Olga, Martel, Anne, Grudinin, Sergei, Soloviov, Dmytro, Kuklin, Alexander, Maksimov, Eugene G., Friedrich, Thomas, Pieper, Jörg
Format: Article
Language:English
Subjects:
B: Biophysical and Biochemical Systems and Processes
Bacterial Proteins - chemistry
Biological Physics
Canthaxanthin
Cyanobacteria - metabolism
Models, Biological
Physics
Scattering, Small Angle
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Summary:We used small-angle neutron scattering partially coupled with size-exclusion chromatography to unravel the solution structures of two variants of the Orange Carotenoid Protein (OCP) lacking the N-terminal extension (OCP-ΔNTE) and its complex formation with the Fluorescence Recovery Protein (FRP). The dark-adapted, orange form OCP-ΔNTEO is fully photoswitchable and preferentially binds the pigment echinenone. Its complex with FRP consists of a monomeric OCP component, which closely resembles the compact structure expected for the OCP ground state, OCPO. In contrast, the pink form OCP-ΔNTEP, preferentially binding the pigment canthaxanthin, is mostly nonswitchable. The pink OCP form appears to occur as a dimer and is characterized by a separation of the N- and C-terminal domains, with the canthaxanthin embedded only into the N-terminal domain. Therefore, OCP-ΔNTEP can be viewed as a prototypical model system for the active, spectrally red-shifted state of OCP, OCPR. The dimeric structure of OCP-ΔNTEP is retained in its complex with FRP. Small-angle neutron scattering using partially deuterated OCP–FRP complexes reveals that FRP undergoes significant structural changes upon complex formation with OCP. The observed structures are assigned to individual intermediates of the OCP photocycle in the presence of FRP.
ISSN:1520-6106
1520-5207
DOI:10.1021/acs.jpcb.2c07182