Structure of a Cyanobacterial BLUF Protein, Tll0078, Containing a Novel FAD-binding Blue Light Sensor Domain

Kita, Akiko; Okajima, Koji; Morimoto, Yukio; Ikeuchi, Masahiko; Miki, Kunio

doi:10.1016/j.jmb.2005.03.067

Cited by 151 publications

(271 citation statements)

References 46 publications

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“…This mechanism also can explain why the photoactivated state is so stable and lives from seconds in Slr1694 to a half-hour in AppA. In support of this hypothesis, mutation of the conserved Tyr or the conserved Gln results in a complete loss of photocycling activity (12,15,16,28,29). With the R. sphaeroides BlrB structure at hand, Jung et al (13) presented an alternative that would imply a light-induced PT from Arg-32 to the O2 of the flavin from FAD*.…”

Section: Discussionmentioning

confidence: 73%

“…Previous studies on flavo-enzymes have revealed that rapid light-driven ET may occur from aromatic residues to flavin (25,26). Tyr-8 (Tyr-21 in AppA) is a good candidate because it is the closest aromatic residue to the flavin and has been shown to be critical for photocycling activity in BLUF domains (12,15,16). The redox properties of flavin and Tyr gives a favorable driving force for the ET reaction: the midpoint potential for flavin͞flavin •Ϫ is approximately Ϫ0.8 V and for Tyr͞Tyr •ϩ is Ϸ0.93 V (25,27), providing a driving force for ET of ⌬G ϭ Ϫ0.62 eV given that the energy of the 0-0 transition of S 0 3 S 1 is Ϸ 2.35 eV (1 eV ϭ 1.602 ϫ 10 Ϫ19 J) (27).…”

Section: Discussionmentioning

confidence: 99%

“…Recently, crystal and solution structures of several BLUF domains were obtained (11)(12)(13)(14). The BLUF domain shows a ferredoxin-like fold consisting of a five-stranded ␤-sheet with two ␣-helices packed on one side of the sheet, with the noncovalently bound isoalloxazine ring of flavin adenine dinucleotide (FAD) positioned between the two ␣-helices.…”

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confidence: 99%

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Hydrogen-bond switching through a radical pair mechanism in a flavin-binding photoreceptor

Gauden

Stokkum²,

Key³

et al. 2006

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

217

435

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BLUF (blue light sensing using FAD) domains constitute a recently discovered class of photoreceptor proteins found in bacteria and eukaryotic algae, where they control a range of physiological responses including photosynthesis gene expression, photophobia, and negative phototaxis. Other than in well known photoreceptors such as the rhodopsins and phytochromes, BLUF domains are sensitive to light through an oxidized flavin rather than an isomerizable cofactor. To understand the physicochemical basis of BLUF domain photoactivation, we have applied femtosecond transient absorption spectroscopy to the Slr1694 BLUF domain of Synechocystis PCC6803. We show that photoactivation of BLUF domains proceeds by means of a radical-pair mechanism, driven by electron and proton transfer from the protein to the flavin, resulting in the transient formation of anionic and neutral flavin radical species that finally result in the long-lived signaling state on a 100-ps timescale. A pronounced deuteration effect is observed on the lifetimes of the intermediate radical species, indicating that proton movements underlie their molecular transformations. We propose a photoactivation mechanism that involves a successive rupture of hydrogen bonds between a conserved tyrosine and glutamine by light-induced electron transfer from tyrosine to flavin and between the glutamine and flavin by subsequent protonation at flavin N5. These events allow a reorientation of the conserved glutamine, resulting in a switching of the hydrogen-bond network connecting the chromophore to the protein, followed by radicalpair recombination, which locks the glutamine in place. It is suggested that the redox potential of flavin generally defines the light sensitivity of flavin-binding photoreceptors.flavoprotein ͉ light sensing ͉ photochemistry ͉ reaction mechanism ͉ spectroscopy

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Section: Discussionmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 99%

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Hydrogen-bond switching through a radical pair mechanism in a flavin-binding photoreceptor

Gauden

Stokkum²,

Key³

et al. 2006

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

217

435

View full text Add to dashboard Cite

show abstract

“…In various x-ray crystal and NMR solution structures (14)(15)(16)(17)(18)28), as well as spectroscopic (13,22,(39)(40)(41) and theoretical (42)(43)(44) studies, the dark-state orientation of Gln-63 has remained ambiguous. As illustrated in Fig.…”

Section: Structure Of the Bluf Domain Of Appamentioning

confidence: 99%

“…More recently, spectroscopic studies of the AppA BLUF domains showed an influence of a N-terminal truncation on the conformation and/or environment of Trp-104 and suggested that the Trp out conformation is a physiologically relevant structure (29). The Trp out conformation has been also observed in several BLUF proteins, such as PixD from Thermosynechococcus elongatus BP-1 (Tll0078) (15) and BlrB from R. sphaeroides (7). Furthermore, the crystal structures of PixD from Synechocystis sp.…”

Section: Introductionmentioning

confidence: 99%

Structural Refinement of a Key Tryptophan Residue in the BLUF Photoreceptor AppA by Ultraviolet Resonance Raman Spectroscopy

Unno¹,

Kikuchi²,

Masuda³

et al. 2010

AIP Conference Proceedings

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The flavin-adenine-dinucleotide-binding BLUF domain constitutes a new class of blue-light receptors, and the N-terminal domain of AppA is a representative of this family. The BLUF domain is of special interest because it uses a rigid flavin rather than an isomerizable chromophore, such as a rhodopsin or phytochrome, for its light-activation process. Crystal and solution structures of several BLUF domains were recently obtained, and their overall structures are consistent. However, there is a key ambiguity regarding the position of a conserved tryptophan (Trp-104 in AppA), in that this residue was found either close to flavin (Trp in conformation) or exposed to the solvent (Trp out conformation). The location of Trp-104 is a crucial factor in understanding the photocycle mechanism of BLUF domains, because this residue has been shown to play an essential role in the activation of AppA. In this study, we demonstrated a Trp in conformation for the BLUF domain of AppA through direct observation of the vibrational spectrum of Trp-104 by ultraviolet resonance Raman spectroscopy, and also observed light-induced conformational and environmental changes in Trp-104. This study provides a structural basis for future investigations of the photocycle mechanism of BLUF proteins.

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Molecular determinant modulates thermal recovery kinetics and structural integrity of the bacterial BLUF photoreceptor

et al. 2016

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Edited by Richard CogdellBLUF domains are flavin-based photoreceptors which receive the blue light signal and are involved in the sensory transduction. We report a short BLUF photoreceptor (SnfB) in Stenotrophomonas sp. We have investigated photodynamic properties of C terminus truncated and several mutated SnfB proteins. Deletion of the extended C-terminal residues alters the thermal recovery kinetics and also affects the integrity of the SnfB protein. Mutagenesis studies demonstrated that the conserved residues within and outside the flavinbinding pocket also regulates the photocycle properties of the protein. These studies suggest that the C-terminal residues outside the BLUF domain can tune the photodynamic properties of the BLUF protein.

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Structure of a Cyanobacterial BLUF Protein, Tll0078, Containing a Novel FAD-binding Blue Light Sensor Domain

Cited by 151 publications

References 46 publications

Hydrogen-bond switching through a radical pair mechanism in a flavin-binding photoreceptor

Hydrogen-bond switching through a radical pair mechanism in a flavin-binding photoreceptor

Structural Refinement of a Key Tryptophan Residue in the BLUF Photoreceptor AppA by Ultraviolet Resonance Raman Spectroscopy

Molecular determinant modulates thermal recovery kinetics and structural integrity of the bacterial BLUF photoreceptor

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