Redox Modulation of Flavin and Tyrosine Determines Photoinduced Proton-coupled Electron Transfer and Photoactivation of BLUF Photoreceptors

Mathes, Tilo; Stokkum, Ivo H. M. van; Stierl, Manuela; Kennis, John T. M.

doi:10.1074/jbc.m112.391896

Cited by 57 publications

(111 citation statements)

References 83 publications

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“…Additionally, all subsequent EADS, including the red spectrum, share an isosbestic point at zero at 479 nm, which suggests a highly concerted reaction to form a photoproduct. The zero crossing in the black spectrum is red shifted to 485 nm, and indicates relaxation of a flavin hot excited state prior to photoproduct formation, as previously observed . The red spectrum exists for ~ 6 ps, and evolves into the blue spectrum, which maintained the same amount of GSB but partly lost its negative SE contribution.…”

Section: Resultssupporting

confidence: 69%

“…C, upper panel) show the high similarity of the spectra in both solvents. The FAD* spectrum nicely reflects the excited state features discussed above, and has lifetimes of 2.9 ps (27%), 9.3 ps (48%) and 41 ps (25%) ( τ avg = 15.5 ps, calculated according to ). The Q1 difference spectrum is representative of an anionic flavin semiquinone with charge transfer (CT) character .…”

Section: Resultsmentioning

confidence: 56%

“…The FAD* spectrum nicely reflects the excited state features discussed above, and has lifetimes of 2.9 ps (27%), 9.3 ps (48%) and 41 ps (25%) ( τ avg = 15.5 ps, calculated according to ). The Q1 difference spectrum is representative of an anionic flavin semiquinone with charge transfer (CT) character . It decays in an H/D isotope‐dependent manner in 7.9/14 ps, with a KIE of ~ 1.8, into the Q2 species, which represents the neutral flavin semiquinone.…”

Section: Resultsmentioning

confidence: 56%

“…This hydrogen bond switch is accomplished by light-induced sequential proton-coupled electron transfer (PCET) from a conserved tyrosine to the flavin (Fig. 1) [3][4][5][6]. After formation of a neutral flavin semiquinone radical, a conserved glutamine changes its conformation and/or tautomerizes to create a new hydrogen bond to the C4=O carbonyl of the flavin [7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

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Photoinduced formation of flavin radicals in BLUF domains lacking the central glutamine

et al. 2015

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Blue light receptors using FAD (BLUFs) facilitate blue light‐induced signal transduction via light‐induced rearrangement of hydrogen bonds between the flavin chromophore and a conserved glutamine side chain. Here, we investigated the photochemistry of the BLUF domain Slr1694 from Synechocystis sp. in which the glutamine side chain was removed. Without the glutamine, no red‐shifted signaling state is formed, but light‐induced proton‐coupled electron transfer between protein and flavin takes place similarly as for the wild‐type protein. However, the lifetime of the neutral flavin semiquinone–tyrosyl radical pair is greatly prolonged from < 100 ps to several nanoseconds, which indicates that the formation of radical intermediates drives the hydrogen bond rearrangement in BLUF photoactivation. Moreover, glutamine plays a central role in the molecular organization of the hydrogen bond network in the flavin‐binding pocket, as its removal enhances electron transfer from tyrosine to the excited flavin, and enables competing electron transfer from a nearby tryptophan.

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Section: Resultssupporting

confidence: 69%

Section: Resultsmentioning

confidence: 56%

Section: Resultsmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

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Photoinduced formation of flavin radicals in BLUF domains lacking the central glutamine

et al. 2015

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“…It has been proposed that in the light state of PixD a concerted electron proton transfer (CEPT) takes place directly leading to the formation of FADH • 35, 37 . In Figure 4, bands at 1512, and 1525 cm −1 are observed within 3 ps, which are assigned to the FAD radical.…”

Section: Resultsmentioning

confidence: 99%

Photoactivation of the BLUF Protein PixD Probed by the Site-Specific Incorporation of Fluorotyrosine Residues

et al. 2017

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The flavin chromophore in blue light using FAD (BLUF) photoreceptors is surrounded by a hydrogen bond network that senses and responds to changes in the electronic structure of the flavin on the ultrafast time scale. The hydrogen bond network includes a strictly conserved Tyr residue, and previously we explored the role of this residue, Y21, in the photoactivation mechanism of the BLUF protein AppABLUF by the introduction of fluorotyrosine (F-Tyr) analogs that modulated the pKa and reduction potential of Y21 by 3.5 pH units and 200 mV, respectively. Although little impact on the forward (dark to light adapted form) photoreaction was observed, the change in Y21 pKa led to a 4,000-fold increase in the rate of dark state recovery. In the present work we have extended these studies to the BLUF protein PixD, where, in contrast to AppABLUF, modulation in the Tyr (Y8) pKa has a profound impact on the forward photoreaction. In particular, a decrease in Y8 pKa by 2 or more pH units prevents formation of a stable light state, consistent with a photoactivation mechanism that involves proton transfer or proton coupled electron transfer from Y8 to the electronically excited FAD. Conversely, the effect of pKa on the rate of dark recovery is markedly reduced in PixD. These observations highlight very significant differences between the photocycles of PixD and AppABLUF, despite their sharing highly conserved FAD binding architectures.

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Computational Spectroscopy, Dynamics, and Photochemistry of Photosensory Flavoproteins

Domratcheva

Udvarhelyi

Shahi

2014

Methods in Molecular Biology

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Extensive interest in photosensory proteins stimulated computational studies of flavins and flavoproteins in the past decade. This review is dedicated to the three central topics of these studies: calculations of flavin UV-visible and IR spectra, simulated dynamics of photoreceptor proteins, and flavin photochemistry. Accordingly, this chapter is divided into three parts; each part describes corresponding computational protocols, summarizes computational results, and discusses the emerging mechanistic picture.

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Redox Modulation of Flavin and Tyrosine Determines Photoinduced Proton-coupled Electron Transfer and Photoactivation of BLUF Photoreceptors

Cited by 57 publications

References 83 publications

Photoinduced formation of flavin radicals in BLUF domains lacking the central glutamine

Photoinduced formation of flavin radicals in BLUF domains lacking the central glutamine

Photoactivation of the BLUF Protein PixD Probed by the Site-Specific Incorporation of Fluorotyrosine Residues

Computational Spectroscopy, Dynamics, and Photochemistry of Photosensory Flavoproteins

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