Excited-state properties of the 16 kDa red carotenoid protein from Arthrospira maxima

Chábera, Pavel; Durchan, Milan; Shih, Patrick M.; Kerfeld, Cheryl A.; Polı́vka, Tomáš

doi:10.1016/j.bbabio.2010.08.013

Cited by 40 publications

(40 citation statements)

References 39 publications

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“…The UV-visible absorption spectra of A. platensis OCP O , OCP R , and of the RCP are shown in Figure 4A. The absorption spectrum of RCP described here differs in some ways from those previously reported (Holt and Krogmann, 1981;Chábera et al, 2011). Significantly less vibronic structure is observed in the S 0 →S 2 transition of the carotenoid in the visible region of the spectrum.…”

Section: Spectroscopic Characterization Of Ocp O Ocp R and Rcpcontrasting

confidence: 48%

Structural and Functional Modularity of the Orange Carotenoid Protein: Distinct Roles for the N- and C-Terminal Domains in Cyanobacterial Photoprotection

et al. 2014

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The orange carotenoid protein (OCP) serves as a sensor of light intensity and an effector of phycobilisome (PB)-associated photoprotection in cyanobacteria. Structurally, the OCP is composed of two distinct domains spanned by a single carotenoid chromophore. Functionally, in response to high light, the OCP converts from a dark-stable orange form, OCP O , to an active red form, OCP R . The C-terminal domain of the OCP has been implicated in the dynamic response to light intensity and plays a role in switching off the OCP's photoprotective response through its interaction with the fluorescence recovery protein. The function of the N-terminal domain, which is uniquely found in cyanobacteria, is unclear. To investigate its function, we isolated the N-terminal domain in vitro using limited proteolysis of native OCP. The N-terminal domain retains the carotenoid chromophore; this red carotenoid protein (RCP) has constitutive PB fluorescence quenching activity comparable in magnitude to that of active, full-length OCP R . A comparison of the spectroscopic properties of the RCP with OCP R indicates that critical proteinchromophore interactions within the C-terminal domain are weakened in the OCP R form. These results suggest that the C-terminal domain dynamically regulates the photoprotective activity of an otherwise constitutively active carotenoid binding N-terminal domain.

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Section: Spectroscopic Characterization Of Ocp O Ocp R and Rcpcontrasting

confidence: 48%

Structural and Functional Modularity of the Orange Carotenoid Protein: Distinct Roles for the N- and C-Terminal Domains in Cyanobacterial Photoprotection

et al. 2014

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“…Absorption of light by (h)ECN triggers a red shift of the OCP absorption and causes significant rearrangement of the protein's tertiary structure. Such a transition is often referred to as a photoconversion of the orange (OCP O ) into the red (OCP R ) form, and it has been attentively studied in vitro by different absorption techniques, due to pronounced changes of the S 0 -S 2 absorption of (h)ECN upon photoconversion (11)(12)(13)(14).…”

Section: Introductionmentioning

confidence: 99%

Fluorescent Labeling Preserving OCP Photoactivity Reveals Its Reorganization during the Photocycle

Maksimov

Sluchanko

Mironov

et al. 2017

Biophysical Journal

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Orange carotenoid protein (OCP), responsible for the photoprotection of the cyanobacterial photosynthetic apparatus under excessive light conditions, undergoes significant rearrangements upon photoconversion and transits from the stable orange to the signaling red state. This is thought to involve a 12-Å translocation of the carotenoid cofactor and separation of the N-and C-terminal protein domains. Despite clear recent progress, the detailed mechanism of the OCP photoconversion and associated photoprotection remains elusive. Here, we labeled the OCP of Synechocystis with tetramethylrhodamine-maleimide (TMR) and obtained a photoactive OCP-TMR complex, the fluorescence of which was highly sensitive to the protein state, showing unprecedented contrast between the orange and red states and reflecting changes in protein conformation and the distances from TMR to the carotenoid throughout the photocycle. The OCP-TMR complex was sensitive to the light intensity, temperature, and viscosity of the solvent. Based on the observed Fö rster resonance energy transfer, we determined that upon photoconversion, the distance between TMR (donor) bound to a cysteine in the C-terminal domain and the carotenoid (acceptor) increased by 18 Å , with simultaneous translocation of the carotenoid into the N-terminal domain. Time-resolved fluorescence anisotropy revealed a significant decrease of the OCP rotation rate in the red state, indicating that the light-triggered conversion of the protein is accompanied by an increase of its hydrodynamic radius. Thus, our results support the idea of significant structural rearrangements of OCP, providing, to our knowledge, new insights into the structural rearrangements of OCP throughout the photocycle and a completely novel approach to the study of its photocycle and non-photochemical quenching. We suggest that this approach can be generally applied to other photoactive proteins.

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“…Moreover, the conjugated carbonyl group of hydroxyechinenone in OCP forms hydrogen bonds to nearby tryptophan and tyrosine residues. These structural changes result in the appearance of the ICT band in the transient absorption spectrum; however, it disappears in the closely related red carotenoid protein, where the part of the protein forming the carbonyl binding site in OCP is missing (39).…”

Section: Resultsmentioning

confidence: 99%

Photoprotection in a purple phototrophic bacterium mediated by oxygen-dependent alteration of carotenoid excited-state properties

Šlouf

Chábera

Olsen³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Carotenoids are known to offer protection against the potentially damaging combination of light and oxygen encountered by purple phototrophic bacteria, but the efficiency of such protection depends on the type of carotenoid. Rhodobacter sphaeroides synthesizes spheroidene as the main carotenoid under anaerobic conditions whereas, in the presence of oxygen, the enzyme spheroidene monooxygenase catalyses the incorporation of a keto group forming spheroidenone. We performed ultrafast transient absorption spectroscopy on membranes containing reaction center-light-harvesting 1-PufX (RC-LH1-PufX) complexes and showed that when oxygen is present the incorporation of the keto group into spheroidene, forming spheroidenone, reconfigures the energy transfer pathway in the LH1, but not the LH2, antenna. The spheroidene/spheroidenone transition acts as a molecular switch that is suggested to twist spheroidenone into an s-trans configuration increasing its conjugation length and lowering the energy of the lowest triplet state so it can act as an effective quencher of singlet oxygen. The other consequence of converting carotenoids in RC-LH1-PufX complexes is that S 2 ∕S 1 ∕triplet pathways for spheroidene is replaced with a new pathway for spheroidenone involving an activated intramolecular charge-transfer (ICT) state. This strategy for RC-LH1-PufX-spheroidenone complexes maintains the light-harvesting cross-section of the antenna by opening an active, ultrafast S 1 ∕ICT channel for energy transfer to LH1 Bchls while optimizing the triplet energy for singlet oxygen quenching. We propose that spheroidene/spheroidenone switching represents a simple and effective photoprotective mechanism of likely importance for phototrophic bacteria that encounter light and oxygen.charge-transfer state | photoprotection | purple bacteria | photosynthesis C arotenoids are natural pigments that absorb light in the 450-550 nm spectral region and transfer the energy to (bacterio) chlorophylls [(B)Chls] thereby acting as important energy donors in photosynthesis (1). In addition to extending the spectral range for absorption of solar energy, carotenoids play a structural role in light-harvesting (antenna) complexes (2, 3). Finally, carotenoids play a photoprotective role by dissipating unwanted excited states in antenna complexes (4, 5). It is well documented that carotenoids in purple phototrophic bacteria perform light-harvesting and structural roles, and the availability of carotenoidless mutants showed early on that carotenoids are essential for protection against oxygen radicals (6, 7). The present study demonstrates the mechanistic basis for photoprotection in photosynthetic bacteria using the purple bacterium Rhodobacter (Rba.) sphaeroides as a model. The photosynthetic complexes of this bacterium form interconnected membrane domains representing ∼4;000 BChl molecules (8-10). The membranes are found within the cell as hundreds of spherical intracytoplasmic membrane vesicles ∼50 nm in diameter (11). Light-harvesting LH2 complexes form the bulk...

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Excited-state properties of the 16 kDa red carotenoid protein from Arthrospira maxima

Cited by 40 publications

References 39 publications

Structural and Functional Modularity of the Orange Carotenoid Protein: Distinct Roles for the N- and C-Terminal Domains in Cyanobacterial Photoprotection

Structural and Functional Modularity of the Orange Carotenoid Protein: Distinct Roles for the N- and C-Terminal Domains in Cyanobacterial Photoprotection

Fluorescent Labeling Preserving OCP Photoactivity Reveals Its Reorganization during the Photocycle

Photoprotection in a purple phototrophic bacterium mediated by oxygen-dependent alteration of carotenoid excited-state properties

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