Ultrafast quenching of tryptophan fluorescence in proteins: Interresidue and intrahelical electron transfer

W, Qiu; Li, Tanping; Zhang, Luyuan; Yang, Yi; Kao, Ya-Ting; Wang, Limin; Zhong, Dongping

doi:10.1016/j.chemphys.2008.01.061

Cited by 75 publications

(66 citation statements)

References 55 publications

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“…In our mechanism, however, it is the [W233 − -W233 + ] radical ion pair state that is instrumental for the breakage of salt bridges that stabilize the dimer structure. By the same argument, the failure of function of this W285F mutant is consistent with the notion that other redox species-for instance, the amides (22,24,36,37) of the protein backbone or, although less probable, the arginines (8)-do hardly substitute as redox partners. Also in line with our mechanism is the recently reported drastic increase of both the fluorescence lifetime and the steady-state quantum yield of Trp in the dimeric mutant W285F of the isolated UVR8 protein compared with its wild type (8).…”

Section: Resultssupporting

confidence: 67%

“…Also We note in passing that the absorption peak of Trp at about 300 nm corresponds to the excitation energy 4.14 eV, which is sufficient to oxidize or reduce nearby species such as aromatic amino acid residues or the protein backbone (24,25). However, we assume that the redox reaction involving two Trps is easier to achieve than other electron transfer reactions within this protein structure.…”

Section: Resultsmentioning

confidence: 99%

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On the mechanism of photoinduced dimer dissociation in the plant UVR8 photoreceptor

Voityuk

Marcus

Michel‐Beyerle

2014

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

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UV-B absorption by the photoreceptor UV resistance locus 8 (UVR8) consisting of two identical protein units triggers a signal chain used by plants in connection with protection and repair of UV-B induced damage. X-ray structural analysis of the purified protein [Christie JM, et al. (2012) Science 335(6075):1492-1496] [Wu D, et al. (2012) Nature 484(7393): 214-220] has revealed that the dimer is held together by arginine-aspartate salt bridges. In this paper we address the initial processes in the signal chain. On the basis of high-level quantum-chemical calculations, we propose a mechanism for the photodissociation of UVR8 that consists of three steps: (i) In each monomer, multiple tryptophans form an extended light-harvesting system in which the L a excited state of Trp233 experiences strong electrostatic stabilization by the protein environment. The strong stabilization singles out this tryptophan to be an efficient exciton acceptor that accumulates the excitation energy from the entire protein subunit. (ii) A fast decay of the locally excited state by charge separation generates the radical ion pair Trp285(+)-Trp233(−) with a dipole moment of ∼18 D. (iii) Key to the proposed mechanism is that this large dipole moment drives the breaking of the salt bridges between the two monomer subunits. The suggested mechanism for the UV-B-driven dissociation of the dimer that rests on the prominent players Trp233 and Trp285 explains the experimental results obtained from mutagenesis of UVR8. L ife on earth depends on sunlight that drives energy conversion and signaling processes, however, at the price that its UV fraction may damage DNA. Counteracting this threat, plants respond to UV-B radiation by the photoreceptor UV resistance locus 8 (UVR8) discovered in Arabidopsis thaliana (1). In the presence of UV-B (280-315 nm), the UVR8 protein accumulates rapidly in the cell nucleus (2, 3). Its interaction with other proteins activates gene expression to protect against or repair UV-B-induced damage (4-7). Unlike other photoreceptors in cells, the protein UVR8 exploits the UV-B absorbance of its intrinsic tryptophans rather than that of exogenic chromophores.The crystal structure of the UVR8 protein (8, 9) revealed that the dimer is held together by salt bridges between the cationic arginine (R) and anionic aspartate (D) or glutamate (E) side chains at the interface between the two subunits. Exposure of UVR8 to UV-B light causes dissociation of the protein into the monomers. This monomerization is universal, because it is observed for the purified protein (8, 9) and in plants and heterologous systems (10). The crystal structure allows one to infer a cooperative role and an interplay of specific tryptophans. It was suggested (11, 12) that excitation of the tryptophan triad W233, W285, and W337 initiates the dissociation of the dimeric photoreceptor and triggers the signal chain used by plants for . Subsequent interactions of monomer subunits with other proteins associated with chromatin have been shown to activate transcription...

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Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 99%

On the mechanism of photoinduced dimer dissociation in the plant UVR8 photoreceptor

Voityuk

Marcus

Michel‐Beyerle

2014

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

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“…This movement may be triggered by either a partial rearrangement of domain II, or a change in the separation of domains II and III which in turn alters the packing structure of domain II. With further addition of denaturant (> 2 M), the big fluorescence intensity drop and red shift of the Trp fluorescence emission is clear evidence that the Trp-212 is more exposed to a more polar environment allowing water molecules to quench the fluorescence, or quenching by other aminoacid residues which can become close to the tryptophan [32][33][34][35]. This is clear evidence that domain II is now being unfolded to a very significant degree.…”

Section: Steady State Analysis Of Bsa and Bsa-ans Denaturationmentioning

confidence: 70%

Monitoring Local Unfolding of Bovine Serum Albumin During Denaturation Using Steady-State and Time-Resolved Fluorescence Spectroscopy

2009

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In a previous report (J. Fluoresc. 16, 153, 2006) we studied the chaotropiclly induced denaturation of Bovine Serum Albumin (BSA) using the fluorescence decay kinetics at different stages in the denaturation of BSA by guanidinium hydrochloride (GuHCl). In this work, we gain a more detailed insight into the BSA denaturation process by investigating the thermodynamics of the process. Structural changes were monitored spectrophotometrically via the intrinsic protein fluorescence from tryptophan residues, and the extrinsic fluorescence from 1,8-anilinonaphthalene sulphonate (ANS). ANS tends to locate in a variety of binding sites in BSA which are located in different domains, and these can be selectively populated using different, 1:1 and 1:10 molar ratios of BSA to ANS. The data from steady-state and time-resolved fluorescence spectroscopy were analyzed using thermodynamic two-state and three-state models and the lifetime data clearly indicated the formation of an intermediate state during denaturation. A global analysis using non-linear regression gave a . The lifetime analysis of the BSA-ANS complexes also shows clearly that there are differences in stability of the BSA domains, with domain III unfolding first at low GuHCl concentrations (<1.5M).

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“…Every protein except A1m-H displayed a short-lifetime component of a few hundred ps, present at all wavelengths. These types of quenching processes have been attributed to Trp interactions with nearby charged residues (37)(38)(39), and the absence of such a feature in A1m-H again indicates that this protein has a local structure different from those of the other eight proteins. The perturbation of local structure and, thus, local solvent exposure can result in different hydration dynamics, making it unreliable to compare the dynamics of A1m-H to those of the other A1m proteins.…”

Section: Resultsmentioning

confidence: 99%

Hydration dynamics at fluorinated protein surfaces

Kwon

Yoo

Othon

et al. 2010

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

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Water-protein interactions dictate many processes crucial to protein function including folding, dynamics, interactions with other biomolecules, and enzymatic catalysis. Here we examine the effect of surface fluorination on water-protein interactions. Modification of designed coiled-coil proteins by incorporation of 5,5,5-trifluoroleucine or (4S)-2-amino-4-methylhexanoic acid enables systematic examination of the effects of side-chain volume and fluorination on solvation dynamics. Using ultrafast fluorescence spectroscopy, we find that fluorinated side chains exert electrostatic drag on neighboring water molecules, slowing water motion at the protein surface.fluorine | noncanonical amino acids | protein engineering | solvation dynamics | ultrafast hydration T he past decade has witnessed substantial expansion in the number and diversity of noncanonical amino acids that can be incorporated into recombinant proteins expressed in bacterial cells (1-3). Fluorinated amino acids have drawn special attention (4-16) because of the unusual solubility properties of fluorinated hydrocarbons. Several independent studies have shown that fluorination of coiled-coil and helix-bundle proteins leads to enhanced stability with respect to thermal or chemical denaturation (6-12), an effect attributed to the hyper-hydrophobic and fluorophilic character of fluorinated amino acid side chains.Although both classes of compounds are hydrophobic, hydrocarbons and fluorocarbons differ in important ways (17)(18)(19)(20)(21)(22). The high electronegativity of fluorine renders the C-F bond both strongly polar and weakly polarizable (17,21,22). The dipole associated with the C-F bond exerts strong inductive effects on neighboring bonds (23) and can form reasonably strong electrostatic interactions with ionic or polar groups when the two moieties are appropriately positioned. The hydrophobic character of fluorinated compounds has been described as "polar hydrophobicity (17)," and is believed to play important roles in organic and medicinal chemistry. Furthermore, the C-F bond is significantly longer than the C-H bond, and the calculated volume of the trifluoromethyl group is about twice that of a methyl group (20). The studies described here constitute an attempt to understand more fully the interaction of water with fluorinated molecular surfaces, and to provide a sound basis for the use of fluorinated amino acids in the engineering of proteins with unique and useful physical properties.The hydration layer adjacent to protein surfaces exhibits properties different from those of bulk water; the more rigid and denser structure of the hydration layer plays a crucial role in protein structure, folding, dynamics, and function (24-26). Elucidation of the dynamic features of this region, on the time scales of atomic and molecular motion, is essential in understanding protein hydration. In the past decade, the knowledge of hydration on protein surfaces has been extensively expanded by studying the dynamic properties of biological water for various pro...

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Ultrafast quenching of tryptophan fluorescence in proteins: Interresidue and intrahelical electron transfer

Cited by 75 publications

References 55 publications

On the mechanism of photoinduced dimer dissociation in the plant UVR8 photoreceptor

On the mechanism of photoinduced dimer dissociation in the plant UVR8 photoreceptor

Monitoring Local Unfolding of Bovine Serum Albumin During Denaturation Using Steady-State and Time-Resolved Fluorescence Spectroscopy

Hydration dynamics at fluorinated protein surfaces

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