Download MendeleyLight activation of Orange Carotenoid Protein reveals bicycle-pedal single-bond isomerization.
Chukhutsina, V.U., Baxter, J.M., Fadini, A., Morgan, R.M., Pope, M.A., Maghlaoui, K., Orr, C.M., Wagner, A., van Thor, J.J.(2022) Nat Commun 13: 6420-6420
- PubMed: 36307413
- DOI: https://doi.org/10.1038/s41467-022-34137-4
- Primary Citation of Related Structures:
7ZSF, 7ZSG, 7ZSH, 7ZSI, 7ZSJ - PubMed Abstract:
Orange 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.
Organizational Affiliation:
Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK.
