Changing Color for Photoprotection: The Orange Carotenoid Protein

Muzzopappa, Fernando; Kirilovsky, Diana

doi:10.1016/j.tplants.2019.09.013

Cited by 91 publications

(71 citation statements)

References 81 publications

(233 reference statements)

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“…It has been recently proposed that population of the S* state is the crucial factor necessary to start the photoconversion [30] . Both Ecn and Ctx are also found in a number of OCP‐related proteins, such as HCP [46,47] or CTDH [48,49] whose functions in cyanobacteria remain unknown [50,51] . On the other hand, Rdx is a major carotenoid from yew fruits [52] with no known function in photosynthesis.…”

Section: Introductionmentioning

confidence: 99%

“…[30] Both Ecn and Ctx are also found in a number of OCP-related proteins, such as HCP [46,47] or CTDH [48,49] whose functions in cyanobacteria remain unknown. [50,51] On the other hand, Rdx is a major carotenoid from yew fruits [52] with no known function in photosynthesis. Yet, it has been used as a model carotenoid to study the S* signal and its role in energy dissipation because of its extreme conjugation length (12 C=C + 2 C=O bonds in a linear conjugated chain), making the S 1 and S* lifetimes clearly different.…”

Section: Introductionmentioning

confidence: 99%

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Excited‐State Evolution of Keto‐Carotenoids after Excess Energy Excitation in the UV Region

et al. 2021

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Carotenoids are molecules with rich photophysics that are in many biological systems involved in photoprotection. Yet, their response to excess energy excitation is only scarcely studied. Here we have explored excited state properties of three keto‐carotenoids, echinenone, canthaxanthin and rhodoxanthin after excess energy excitation to a singlet state absorbing in UV. Though the basic spectral features and kinetics of S2, hot S1, relaxed S1 states remain unchanged upon UV excitation, the clear increase of the S* signal is observed after excess energy excitation, associated with increased S* lifetime. A multiple origin of the S* signal, originating either from specific conformations in the S1 state or from a non‐equilibrated ground state, is confirmed in this work. We propose that the increased amount of energy stored in molecular vibrations, induced by the UV excitation, is the reason for the enhanced S* signal observed after UV excitation. Our data also suggest that a fraction of the UV excited state population may proceed through a non‐sequential pathway, bypassing the S2 state.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Excited‐State Evolution of Keto‐Carotenoids after Excess Energy Excitation in the UV Region

et al. 2021

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“…In line with the static X-ray crystallography data of the basal OCP form and the individual carotenoid-bound NTD 40 , and a FRET-based study on the rhodamine-labeled full-length OCP 41 , it is assumed that the non-bonded (turned loose) carotenoid can slide from the CTD into the NTD, changing its position by more than 10 Å 36 , 39 – 41 , while the protein structure still stays compact. After that, protein–protein interactions become weakened, eventually leading to a complete separation of the CTD and NTD after the so-called N-terminal extension (NTE) detaches from its specific binding site on the CTD 42 – 44 and unfolds as well as another short helical C-terminal tail (CTT) 45 . Detachment of NTE enables interactions of OCP with another regulator called the Fluorescence Recovery Protein (FRP), which properly reassembles the OCP domains to promote the reformation of the inactive orange state and, therefore, switching off the OCP-mediated phycobilisome quenching 46 – 50 .…”

Section: Introductionmentioning

confidence: 99%

Probing of carotenoid-tryptophan hydrogen bonding dynamics in the single-tryptophan photoactive Orange Carotenoid Protein

Maksimov

Protasova

Tsoraev

et al. 2020

Sci Rep

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the photoactive orange carotenoid protein (ocp) plays a key role in cyanobacterial photoprotection. In OCP, a single non-covalently bound keto-carotenoid molecule acts as a light intensity sensor, while the protein is responsible for forming molecular contacts with the light-harvesting antenna, the fluorescence of which is quenched by OCP. Activation of this physiological interaction requires signal transduction from the photoexcited carotenoid to the protein matrix. Recent works revealed an asynchrony between conformational transitions of the carotenoid and the protein. Intrinsic tryptophan (Trp) fluorescence has provided valuable information about the protein part of OCP during its photocycle. However, wild-type OCP contains five Trp residues, which makes extraction of site-specific information impossible. In this work, we overcame this problem by characterizing the photocycle of a fully photoactive OCP variant (OCP-3FH) with only the most critical tryptophan residue (Trp-288) in place. Trp-288 is of special interest because it forms a hydrogen bond to the carotenoid's keto-oxygen to keep OCP in its dark-adapted state. Using femtosecond pump-probe fluorescence spectroscopy we analyzed the photocycle of OCP-3FH and determined the formation rate of the very first intermediate suggesting that generation of the recently discovered S* state of the carotenoid in OCP precedes the breakage of the hydrogen bonds. Therefore, following Trp fluorescence of the unique photoactive OCP-3FH variant, we identified the rate of the H-bond breakage and provided novel insights into early events accompanying photoactivation of wild-type OCP. The regulation of excitation energy flows in photosynthetic organisms plays a crucial role for improving biomass production in changing environmental conditions 1. Carotenoids as essential photosynthetic pigments can contribute to light-harvesting or act as excitation quenchers depending on the structural organization of antennas and the carotenoid state 2 , resulting in excitation energy transfer (EET) to or from chlorophylls, respectively. EET can be conducted by several mechanisms: transfer to (or from) the carotenoid S 1 excited level 3 , exciton coupling 4,5 and charge transfer 6,7. Although functional roles of carotenoids in light-harvesting antennas are clear, there are still debates considering the involvement of specific EET mechanisms in these roles. The situation is additionally complicated by non-Condon nature of the pigment interaction with regard to wave-like EET process and the occurrence of excitation energy coherence 8,9. Regulation of light-harvesting depends on pH 10 , carotenoid content 11 , lipid content 12 , protein-protein interactions 13 , and other factors 14 , thus highlighting the central role

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“…OCP is composed of two domains, N-terminal domain (NTD) and C-terminal domain (CTD), connected by a flexible loop linker 72 . Both domains have their own paralogs with either stand-alone NTD or CTD; the former is called helical carotenoid protein (HCP) and the latter CTD-like proteins (CTDHs) 72 . Anthocerobacter has one OCP and one NTD, but no CTDH.…”

Section: Phylogeny Of Orange Carotenoid Proteins (Ocp)mentioning

confidence: 99%

Revisiting the early evolution of Cyanobacteria with a new thylakoid-less and deeply diverged isolate from a hornwort

Rahmatpour

Hauser

Nelson

et al. 2021

Preprint

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Cyanobacteria have played pivotal roles in Earth's geological history especially during the rise of atmospheric oxygen. However, our ability to infer the early transitions in Cyanobacteria evolution has been limited by their extremely lopsided tree of life-the vast majority of extant diversity belongs to Phycobacteria (or "crown Cyanobacteria"), while its sister lineage, Gloeobacteria, is depauperate and contains only two closely related species of Gloeobacter and a metagenome-assembled genome. Here we describe a new culturable member of Gloeobacteria, Anthocerobacter panamensis, isolated from a tropical hornwort. Anthocerobacter diverged from Gloeobacter over 1.4 billion years ago and has low 16S identities with environmental samples. Our ultrastructural, physiological, and genomic analyses revealed that this species possesses a unique combination of traits that are exclusively shared with either Gloeobacteria or Phycobacteria. For example, similar to Gloeobacter, it lacks thylakoids and circadian clock genes, but the carotenoid biosynthesis pathway is typical of Phycobacteria. Furthermore, Anthocerobacter has one of the most reduced gene sets for photosystems and phycobilisomes among Cyanobacteria. Despite this, Anthocerobacter is capable of oxygenic photosynthesis under a wide range of light intensities, albeit with much less efficiency. Given its key phylogenetic position, distinct trait combination, and availability as a culture, Anthocerobacter opens a new window to further illuminate the dawn of oxygenic photosynthesis.

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Changing Color for Photoprotection: The Orange Carotenoid Protein

Cited by 91 publications

References 81 publications

Excited‐State Evolution of Keto‐Carotenoids after Excess Energy Excitation in the UV Region

Excited‐State Evolution of Keto‐Carotenoids after Excess Energy Excitation in the UV Region

Probing of carotenoid-tryptophan hydrogen bonding dynamics in the single-tryptophan photoactive Orange Carotenoid Protein

Revisiting the early evolution of Cyanobacteria with a new thylakoid-less and deeply diverged isolate from a hornwort

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