7zsf | pdb_00007zsf
Structure of Orange Carotenoid Protein with canthaxanthin bound
Structural highlights
FunctionOCP_SYNY3 Acts as a photo-protectant. Essential for inhibiting white and blue-green light non-photochemical quenching (NPQ). Binding carotenoids improves OCP's intrinsic photoprotectant activity by broadening its absorption spectrum and facilitating the dissipation of absorbed energy.[1] Publication Abstract from PubMedOrange Carotenoid protein (OCP) is the only known photoreceptor which uses carotenoid for its activation. It is found exclusively in cyanobacteria, where it functions to control light-harvesting of the photosynthetic machinery. However, the photochemical reactions and structural dynamics of this unique photosensing process are not yet resolved. We present time-resolved crystal structures at second-to-minute delays under bright illumination, capturing the early photoproduct and structures of the subsequent reaction intermediates. The first stable photoproduct shows concerted isomerization of C9'-C8' and C7'-C6' single bonds in the bicycle-pedal (s-BP) manner and structural changes in the N-terminal domain with minute timescale kinetics. These are followed by a thermally-driven recovery of the s-BP isomer to the dark state carotenoid configuration. Structural changes propagate to the C-terminal domain, resulting, at later time, in the H-bond rupture of the carotenoid keto group with protein residues. Solution FTIR and UV/Vis spectroscopy support the single bond isomerization of the carotenoid in the s-BP manner and subsequent thermal structural reactions as the basis of OCP photoreception. Light activation of Orange Carotenoid Protein reveals bicycle-pedal single-bond isomerization.,Chukhutsina VU, Baxter JM, Fadini A, Morgan RM, Pope MA, Maghlaoui K, Orr CM, Wagner A, van Thor JJ Nat Commun. 2022 Oct 28;13(1):6420. doi: 10.1038/s41467-022-34137-4. PMID:36307413[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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