Early molecular events in the photoactive yellow protein: role of the chromophore photophysics

Changenet‐Barret, Pascale; Espagne, Agathe; Charier, Sandrine; Baudin, Jean‐Bernard; Jullien, Ludovic; Plaza, Pascal; Hellingwerf, Klaas J.; Martin, Monique M.

doi:10.1039/b400398e

Cited by 54 publications

(102 citation statements)

References 52 publications

(65 reference statements)

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“…For WT and its mutants, neither the fluorescence spectra 59-62 nor the stimulated emission exhibit significant dynamical Stokes shift within the time resolution of our apparatus. 5,11,29 The shift or reshaping of the other absorption bands cannot be fully excluded but, as discussed in a former letter, 11 we rather believe the triexponential decays of the SE signal to arise from the existence of groundstate conformational heterogeneities leading, upon excitation, to excited-state heterogeneities. This hypothesis is consistent with NMR studies of WT in solution, which show that the protein is found to have many different conformations.…”

Section: Time-resolved Transient Absorbance Spectramentioning

confidence: 96%

Structural Effects on the Ultrafast Photoisomerization of Photoactive Yellow Protein. Transient Absorption Spectroscopy of Two Point Mutants

et al. 2009

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Subpicosecond transient absorption spectroscopy was used to address the role of the local environment on the photoisomerization process of the p-coumaric thioester chromophore in photoactive yellow protein (PYP) by studying two point mutants, T50V and E46Q. These mutations introduce alterations of the hydrogen-bond network involving the amino acids of the active site close to the chromophore and the chromophore phenolate group, respectively. Transient-absorption spectra of T50V and E46Q are found to be qualitatively similar to those of the wild-type PYP (WT) and R52Q, suggesting that the earliest steps of the photoinduced processes in all three mutants remain similar to those of the WT. Target analyses of the transient spectra of T50V, E46Q, R52Q, and WT, were successfully performed by using a model based on the one previously published by Larsen et al. (Biophys. J. 2004, 87, 1858, which involves heterogeneous excited-state populations undergoing deactivation along two competitive relaxation pathways. A so-called reactive pathway leads to the sequential formation of the well-characterized cis intermediates, I 0 and I 1 , of the photocycle. The second pathway is non reactive and produces a transient species that restores the initial trans ground-state in 3-6 ps. This transient is tentatively attributed to a distorted vibrationally hot trans ground state. The most prominent effect of mutation is observed for T50V and R52Q which exhibit significantly slower excited-state deactivations, whereas E46Q behaves like the WT protein. This difference is analyzed in terms of a significant decrease, in T50V and R52Q, of the fraction of heterogeneous excited-state population that undergoes isomerization. The quantum yield of isomerization deduced from the target analyses was found to be 0.31 ( 0.08 for WT, 0.22 ( 0.06 for T50V, 0.29 ( 0.08 for E46Q, and 0.19 ( 0.05 for R52Q. The decrease of isomerization yield observed in T50V and R52Q is mainly attributed to the loss of rigidity of the protein active site, induced by these mutations, rather than to the deletion of the positive charge of Arg52 in R52Q.

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Section: Time-resolved Transient Absorbance Spectramentioning

confidence: 96%

Structural Effects on the Ultrafast Photoisomerization of Photoactive Yellow Protein. Transient Absorption Spectroscopy of Two Point Mutants

et al. 2009

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“…Previous time-resolved pump-probe spectroscopy studies have been performed on hydroxycinnamic acids, though much of this work has been focused upon the archetypal p-coumaric acid (3-(4-hydroxyphenyl)-2-propenoic acid) as either the isolated molecule or a functionalized chromophore to mimic the photoactive yellow protein. [20][21][22][23][24][25][26][27] In these studies p-coumaric acid was excited to the first excited electronic state (1 1 pp*, S 1 ). The main relaxation pathway of the 1 1 pp* state was identified as a trans-cis photoisomerization resulting in the formation of the cisphotoproduct.…”

Section: Introductionmentioning

confidence: 99%

Photodynamics of potent antioxidants: ferulic and caffeic acids

Baker

Quan

Greenough

et al. 2016

Phys. Chem. Chem. Phys.

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The dynamics of ferulic acid (3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid) and caffeic acid (3-(3,4-dihydroxyphenyl)-2-propenoic acid) in acetonitrile, dioxane and water at pH 2.2 following photoexcitation to the first excited singlet state are reported. These hydroxycinnamic acids display both strong ultraviolet absorption and potent antioxidant activity, making them promising sunscreen components. Ferulic and caffeic acids have previously been shown to undergo trans-cis photoisomerization via irradiation studies, yet time-resolved measurements were unable to observe formation of the cis-isomer. In the present study, we are able to observe the formation of the cis-isomer as well as provide timescales of relaxation following initial photoexcitation.

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“…This complexity can be reduced if the chromophore in its true anionic, not neutral, structure can be studied free of perturbations. With model compounds, the solvent effect can be assessed by studying them in the solution phase (14)(15)(16)(17)(18). However, the nature of intramolecular change and the timescales involved are still unknown.…”

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Primary steps of the photoactive yellow protein: Isolated chromophore dynamics and protein directed function

Lee

Zewail

2006

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

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The cycle of the photoactive yellow protein (PYP) has been extensively studied, but the dynamics of the isolated chromophore responsible for transduction is unknown. Here, we present realtime observation of the dynamics of the negatively charged chromophore and detection of intermediates along the path of transto-cis isomerization using femtosecond mass selection͞electron detachment techniques. The results show that the role of the protein environment is not in the first step of double-bond twisting (barrier crossing) but in directing efficient conversion to the cisstructure and in impeding radical formation within the protein.femtobiology ͉ transduction ͉ molecular dynamics ͉ photoelectron spectroscopy P hotoactive yellow protein (PYP) is a water-soluble photoreceptor found in Halorhodospira halophila and related halophilic bacterial species (1). The chromophore responsible for perception of light and phototactic response is a deprotonated trans-4-hydroxycinnamic acid (also known as p-coumaric acid) covalently linked to a cysteine residue of the protein via a thioester bond (Fig. 1). Light absorption of the PYP chromophore leads to the initiation of a complex photocycle involving several intermediates. With a variety of biophysical techniques (2-5), it is concluded that the first intermediate (I 0 ) in the photocycle is formed within a few picoseconds, with the chromophore changing to the cis configuration, in a trans-to-cis isomerization process (7-11). The intermediates at longer times have been trapped and identified by x-ray crystallography (12, 13).The critical change of the chromophore in the primary process of isomerization is accompanied or followed by several other processes: proton transfer, protein conformational change, solvation, and disruption of hydrogen-bonding. This complexity can be reduced if the chromophore in its true anionic, not neutral, structure can be studied free of perturbations. With model compounds, the solvent effect can be assessed by studying them in the solution phase (14-18). However, the nature of intramolecular change and the timescales involved are still unknown. It is, therefore, desirable to study the primary isomerization dynamics of the PYP chromophore in isolation, especially in view of the fact that the mechanism for forming the first intermediate (I 0 ) is debatable (2). A gas-phase spectroscopic study has already been reported (19), but it was for the neutral molecule, not the anion structure in the protein.In this work, we report direct observation of the dynamics of the isolated PYP anionic chromophore. To disentangle the role of protein binding and distant torsions, we preserved the central structure involved in the isomerization about the double bond but use the CH 3 group for termination (see Fig. 1). The chromophore, hereafter called P, is excited with a femtosecond pulse from its ground state, the dark state in the protein, to the trans configuration using the mass-selected ions. For probing we use another femtosecond pulse to photodetach and resolve the phot...

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Early molecular events in the photoactive yellow protein: role of the chromophore photophysics

Cited by 54 publications

References 52 publications

Structural Effects on the Ultrafast Photoisomerization of Photoactive Yellow Protein. Transient Absorption Spectroscopy of Two Point Mutants

Structural Effects on the Ultrafast Photoisomerization of Photoactive Yellow Protein. Transient Absorption Spectroscopy of Two Point Mutants

Photodynamics of potent antioxidants: ferulic and caffeic acids

Primary steps of the photoactive yellow protein: Isolated chromophore dynamics and protein directed function

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