Conservation and diversity in the secondary forward photodynamics of red/green cyanobacteriochromes†

Jenkins, Adam J.; Gottlieb, Sean M.; Chang, Chi Wei; Hayer, Randeep J.; Martin, Shelley S.; Lagarias, J. Clark; Larsen, Delmar S.

doi:10.1039/c9pp00295b

Cited by 9 publications

(33 citation statements)

References 45 publications

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“…The region in between (550-620 nm) contains overlapping contributions from ESA and GSB. Similar excited-state spectra were also obtained for several related red/green CBCRs from Nostoc punctiforme, albeit with large variations in lifetimes [41][42][43][44]. In the lifetime analysis of Slr-g3, a local maximum of D is observed at 600 ps, and global fitting resulted in an optimized time constant of 540 ps (τ 1 , see table I).…”

Section: Resultssupporting

confidence: 64%

“…In the present case of a red/green CBCR, we find a number of intermediate states in the nanosecond regime that involve structural rearrangements of the protein surroundings. These rearrangements are potentially involved in signal transduction to a catalytic domain and the allosteric regulation process, which appears to be very variable in different bilin-photoreceptors [44,59]. The regular residuals of the two fits are plotted below the graphs.…”

Section: Protein Adjustments In the Nanosecond Regimementioning

confidence: 99%

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Nanosecond protein dynamics in a red/green cyanobacteriochrome revealed by transient IR spectroscopy

Buhrke

Oppelt

et al. 2020

The Journal of Chemical Physics

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Over the last decades, photoreceptive proteins were extensively studied with biophysical methods to gain a fundamental understanding of their working mechanisms and further guide the development of optogenetic tools. Time-resolved infrared (IR) spectroscopy is one of the key methods to access their functional non-equilibrium processes with high temporal resolution but has the major drawback that experimental data are usually highly complex. Linking the spectral response to specific molecular events is a major obstacle. Here, we investigate a cyanobacteriochrome photoreceptor with a combined approach of transient absorption spectroscopy in the visible and IR spectral regions. We obtain kinetic information in both spectral regions by analysis with two different fitting methods: global multiexponential fitting and lifetime analysis. We investigate the ground state dynamics that follow photoexcitation in both directions of the bi-stable photocycle (Pr* and Pg*) in the nanosecond and microsecond time regimes. We find two ground state intermediates associated with the decay of Pr* and four with Pg* and report the macroscopic time constants of their interconversions. One of these processes is assigned to a structural change in the protein backbone.

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Section: Resultssupporting

confidence: 64%

Section: Protein Adjustments In the Nanosecond Regimementioning

confidence: 99%

Nanosecond protein dynamics in a red/green cyanobacteriochrome revealed by transient IR spectroscopy

Buhrke

Oppelt

et al. 2020

The Journal of Chemical Physics

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“…These spectral trends were observed to be nearly conserved across eight red/green CBCRs isolated from N. punctiforme. 29 The reverse reaction of both CBCRs consisted of nonmonotonic spectral evolution in which the first intermediate was red-shifted from the GSB that initially blue-shifted prior to red-shifting through at least one intermediate before populating the 15Z P r photoproduct (Figures 9, 10, and 12). Despite the overall similarities, we observed key differences in the photochemical dynamics of the two proteins.…”

Section: ■ Discussionmentioning

confidence: 99%

“…Class III F CBCRs (NpAF142g2, B2JAQ4; NpR4776g3, B2IZ18; NpF2854g3, B2IVK2; and NpF2164g4, B2J668) yield Lumi-R f photointermediates that yield blue-shifted Meta-R y intermediates on a nanosecond time scale prior to stable photoproduct formation. For this class, Meta-R y was the first of several subsequent blue-shifted intermediates that were associated with stepwise structural deformation of the chromophore. , In some cases, secondary forward dynamics analyses of the red/green CBCRs also resolved a nonproductive 15 Z P o subpopulation that generated a Lumi-O f photointermediate that decayed back to the ground state. , As with primary forward dynamics investigations, the primary reverse dynamics of several red/green CBCRs resolved three classes. Class I R (NpF2164g6) resolved only a red-shifted Lumi-G o intermediate.…”

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confidence: 85%

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Comparison of the Forward and Reverse Photocycle Dynamics of Two Highly Similar Canonical Red/Green Cyanobacteriochromes Reveals Unexpected Differences

et al. 2021

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Cyanobacteriochromes (CBCRs) are cyanobacterial photoreceptors that exhibit photochromism between two states: a thermally stable dark-adapted state and a metastable light-adapted state with bound linear tetrapyrrole (bilin) chromophores possessing 15Z and 15E configurations, respectively. The photodynamics of canonical red/green CBCRs have been extensively studied; however, the time scales of their excited-state lifetimes and subsequent ground-state evolution rates widely differ and, at present, remain difficult to predict. Here, we compare the photodynamics of two closely related red/green CBCRs that have substantial sequence identity (∼68%) and similar chromophore environments: AnPixJg2 from Anabaena sp. PCC 7120 and NpR6012g4 from Nostoc punctiforme. Using broadband transient absorption spectroscopy on the primary (125 fs to 7 ns) and secondary (7 ns to 10 ms) time scales together with global analysis modeling, our studies revealed that AnPixJg2 and NpR6012g4 have comparable quantum yields for initiating the forward ( 15Z P r → 15E P g ) and reverse ( 15E P g → 15Z P r ) reactions, which proceed through monotonic and nonmonotonic mechanisms, respectively. In addition to small discrepancies in the kinetics, the secondary reverse dynamics resolved unique features for each domain: intermediate shunts in NpR6012g4 and a Meta-G f intermediate redshifted from the 15Z P r photoproduct in AnPixJg2. Overall, this study supports the conclusion that sequence similarity is a useful criterion for predicting pathways of the light-induced evolution and quantum yield of generating primary intermediate Φ p within subfamilies of CBCRs, but more studies are still needed to develop a comprehensive molecular level understanding of these processes.

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Rotameric Heterogeneity of Conserved Tryptophan Is Responsible for Reduced Photochemical Quantum Yield in Cyanobacteriochrome Slr1393g3

Köhler,

Trunk,

Rohr

et al. 2024

ChemPhysChem

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The red/green cyanobacteriochrome (CBCR) slr1393g3 exhibits a quantum yield of only 8% for its forward photoconversion significantly lower than other species from the same CBCR subfamily. The cause for this reduced photoconversion is not yet clear, although in the related NpR6012g4 dark‐state structural heterogeneity of a paramount Trp residue has been proposed to cause the formation of nonproductive subpopulation. However, there is no such information on the equivalent residue in slr1393g3, W496. Here we use solid‐state NMR to explore all possible sidechain rotamers of this Trp residue and their local interactions at the atomic level. The indole nitrogen (Nε1) is used as an NMR probe, achieved by site‐specific 15N‐indole labeling of a quadruply Trp‐deleted variant and trehalose vitrification technique. The data reveal a set of seven indole rotamers of W496 with four distinct environments for the Nε1‐H group. Only a minority population of 20% is found to retain the π‐stacking and hydrogen‐bonding interactions with the chromophore in the dark state that has been assigned to account for complete forward photoconversion. Our results demonstrate the direct role of W496 in modulating the forward quantum yield of slr1393g3 via rearrangement of its sidechain rotameric conformations.

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Conservation and diversity in the secondary forward photodynamics of red/green cyanobacteriochromes†

Abstract: The forward secondary dynamics of eight cyanobacteriochrome domains were characterized, revealing that half of them incorporate an unproductive 15ZPo subpopulation and that a nearly conserved mechanism of blue-shifting intermediates is revealed.

Cited by 9 publications

References 45 publications

Nanosecond protein dynamics in a red/green cyanobacteriochrome revealed by transient IR spectroscopy

Nanosecond protein dynamics in a red/green cyanobacteriochrome revealed by transient IR spectroscopy

Comparison of the Forward and Reverse Photocycle Dynamics of Two Highly Similar Canonical Red/Green Cyanobacteriochromes Reveals Unexpected Differences

Rotameric Heterogeneity of Conserved Tryptophan Is Responsible for Reduced Photochemical Quantum Yield in Cyanobacteriochrome Slr1393g3

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