Light‐Activated Intracellular Movement of Phytochrome

Schäfer, Eberhard; Nagy, Ferenc

doi:10.1002/352760510x.ch9

Cited by 2 publications

(1 citation statement)

References 26 publications

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“…Most intriguing, however, is the ability of CBCRs to tune their absorption over the entire range of the visible spectrum, including near-IR and near-UV [ 12 , 17 , 18 , 19 , 20 ]. The treasure of photosensors provided by nature with which organisms adapt to their environment bears high utility for biochemical applications in bioimaging and optogenetics, but also in therapy and catalysis [ 14 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ].…”

Section: Introductionmentioning

confidence: 99%

Carbon Atoms Speaking Out: How the Geometric Sensitivity of 13C Chemical Shifts Leads to Understanding the Colour Tuning of Phycocyanobilin in Cph1 and AnPixJ

Jähnigen

Sebastiani

2020

Molecules

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We present a combined quantum mechanics/molecular mechanics (QM/MM) molecular dynamics–statistical approach for the interpretation of nuclear magnetic resonance (NMR) chemical shift patterns in phycocyanobilin (PCB). These were originally associated with colour tuning upon photoproduct formation in red/green-absorbing cyanobacteriochrome AnPixJg2 and red/far-red-absorbing phytochrome Cph1Δ2. We pursue an indirect approach without computation of the absorption frequencies since the molecular geometry of cofactor and protein are not accurately known. Instead, we resort to a heuristic determination of the conjugation length in PCB through the experimental NMR chemical shift patterns, supported by quantum chemical calculations. We have found a characteristic correlation pattern of 13C chemical shifts to specific bond orders within the π-conjugated system, which rests on the relative position of carbon atoms with respect to electron-withdrawing groups and the polarisation of covalent bonds. We propose the inversion of this regioselective relationship using multivariate statistics and to apply it to the known experimental NMR chemical shifts in order to predict changes in the bond alternation pattern. Therefrom the extent of electronic conjugation, and eventually the change in absorption frequency, can be derived. In the process, the consultation of explicit mesomeric formulae plays an important role to qualitatively account for possible conjugation scenarios of the chromophore. While we are able to consistently associate the NMR chemical shifts with hypsochromic and bathochromic shifts in the Pg and Pfr, our approach represents an alternative method to increase the explanatory power of NMR spectroscopic data in proteins.

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Section: Introductionmentioning

confidence: 99%

Carbon Atoms Speaking Out: How the Geometric Sensitivity of 13C Chemical Shifts Leads to Understanding the Colour Tuning of Phycocyanobilin in Cph1 and AnPixJ

Jähnigen

Sebastiani

2020

Molecules

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Genetic and Molecular Analysis of Phytochromes from the Filamentous FungusNeurospora crassa

et al. 2005

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Phytochromes (Phys) comprise a superfamily of red-/far-red-light-sensing proteins. Whereas higher-plant Phys that control numerous growth and developmental processes have been well described, the biochemical characteristics and functions of the microbial forms are largely unknown. Here, we describe analyses of the expression, regulation, and activities of two Phys in the filamentous fungus Neurospora crassa. In addition to containing the signature N-terminal domain predicted to covalently associate with a bilin chromophore, PHY-1 and PHY-2 contain C-terminal histidine kinase and response regulator motifs, implying that they function as hybrid two-component sensor kinases activated by light. A bacterially expressed N-terminal fragment of PHY-2 covalently bound either biliverdin or phycocyanobilin in vitro, with the resulting holoprotein displaying red-/far-red-light photochromic absorption spectra and a photocycle in vitro. cDNA analysis of phy-1 and phy-2 revealed two splice isoforms for each gene. The levels of the phy transcripts are not regulated by light, but the abundance of the phy-1 mRNAs is under the control of the circadian clock. Phosphorylated and unphosphorylated forms of PHY-1 were detected; both species were found exclusively in the cytoplasm, with their relative abundances unaffected by light. Strains containing deletions of phy-1 and phy-2, either singly or in tandem, were not compromised in any known photoresponses in Neurospora, leaving their function(s) unclear.Light is essential for life on earth, serving as a primary energy source for organisms ranging from single-celled bacteria to higher plants. Plants, in particular, contain a complex network of light perception and signal transduction systems that enables them to track and respond to fluctuations in multiple parameters within their light environment, including intensity, directionality, daily duration, and spectral quality. Plants employ at least three photoreceptor types for light perception, the cryptochromes and phototropins, which monitor the blue/UV region of the spectrum, and the phytochromes (Phys), which monitor the red-light (R)/far-red-light (FR) region (52). The generic Phy in higher plants is a soluble homodimer, consisting of two ϳ120-kDa polypeptides, each bearing a single bilin (or linear tetrapyrrole) chromophore. The bilin is bound covalently by an autocatalytic mechanism to an N-terminal pocket that, once assembled, serves as the sensory module (73). Through interactions between the bilin and the apoprotein, Phys reversibly photointerconvert between two stable conformers, an R-absorbing Pr form that is biologically inactive and an FR-absorbing Pfr form that is biologically active. Via interconversion between Pr and Pfr, Phys act as reversible switches in photoperception. The C-terminal half of Phys bears contacts for dimerization and sensory output activities, the nature of which is currently unclear (reviewed in references 58 and 71).The deluge of genomic sequence information has greatly expanded the Phy family, with n...

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Light‐Activated Intracellular Movement of Phytochrome

Cited by 2 publications

References 26 publications

Carbon Atoms Speaking Out: How the Geometric Sensitivity of 13C Chemical Shifts Leads to Understanding the Colour Tuning of Phycocyanobilin in Cph1 and AnPixJ

Carbon Atoms Speaking Out: How the Geometric Sensitivity of 13C Chemical Shifts Leads to Understanding the Colour Tuning of Phycocyanobilin in Cph1 and AnPixJ

Genetic and Molecular Analysis of Phytochromes from the Filamentous FungusNeurospora crassa

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