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Tryptophan fluorescence monitors structural changes accompanying signalling state formation in the photocycle of photoactive yellow protein.
Photochem Photobiol Sci. 2004 Jun; 3(6):531-6.PP

Abstract

Photoactive yellow protein, a small, water-soluble blue-light absorbing photoreceptor protein from Ectothiorhodospira(Halorhodospira)[space]halophila has a structure with two hydrophobic cores, of which the main one houses its light-sensitive chromophore (p-coumaric acid), separated by a central [small beta]-sheet. This photoreceptor protein contains a single tryptophan residue (W119) that is situated at the interface between the central beta-sheet and its N-terminal cap. The fluorescence properties of W119 in the dark state pG (lambda(max)= 328 nm; Phi(fl)= 0.01; nearly pH-independent) are typical for a buried tryptophan in a hydrophobic environment with significant quenching by nearby amino acid residues. Signalling state formation leads to pH-dependent fluorescence changes: At pH values <6.5 the fluorescence emission increases, with a minor blue shift of the emission maximum. Above this pH, the emission maximum of the tryptophan shifts considerably to the red, whereas its total intensity decreases. These results further support the contention that signalling state formation in PYP leads to significant changes in the structure of this protein, even at sites that are at a considerable distance from the chromophore. The nature of these changes in pB, however, depend upon the pH imposed upon the protein: At slightly alkaline pH, which presumably is closest to the pH to which this protein is exposed in vivo, these changes lead to an exposure of the part of the central beta-sheet harbouring W119. At slightly acidic pH the polarity of the environment of W119 is hardly affected by the formation of the signalling state but the quenching of its fluorescence emission, possibly by nearby amino acids, is reduced. On the other hand, its accessibility for quenching by small molecules in the solution is enhanced at acidic and alkaline pH in the signalling state (pB) compared to the dark state (pG). This latter observation points towards a more flexible structure of the N-terminal cap, having a looser interaction with the central beta-sheet in pB.

Authors+Show Affiliations

Institute of Biological Information Processing 1--Cellular Signalling, Research Centre Jülich, Germany.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

15170481

Citation

Gensch, Thomas, et al. "Tryptophan Fluorescence Monitors Structural Changes Accompanying Signalling State Formation in the Photocycle of Photoactive Yellow Protein." Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology, vol. 3, no. 6, 2004, pp. 531-6.
Gensch T, Hendriks J, Hellingwerf KJ. Tryptophan fluorescence monitors structural changes accompanying signalling state formation in the photocycle of photoactive yellow protein. Photochem Photobiol Sci. 2004;3(6):531-6.
Gensch, T., Hendriks, J., & Hellingwerf, K. J. (2004). Tryptophan fluorescence monitors structural changes accompanying signalling state formation in the photocycle of photoactive yellow protein. Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology, 3(6), 531-6.
Gensch T, Hendriks J, Hellingwerf KJ. Tryptophan Fluorescence Monitors Structural Changes Accompanying Signalling State Formation in the Photocycle of Photoactive Yellow Protein. Photochem Photobiol Sci. 2004;3(6):531-6. PubMed PMID: 15170481.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Tryptophan fluorescence monitors structural changes accompanying signalling state formation in the photocycle of photoactive yellow protein. AU - Gensch,Thomas, AU - Hendriks,Johnny, AU - Hellingwerf,Klaas J, Y1 - 2004/05/06/ PY - 2004/6/2/pubmed PY - 2005/7/22/medline PY - 2004/6/2/entrez SP - 531 EP - 6 JF - Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology JO - Photochem Photobiol Sci VL - 3 IS - 6 N2 - Photoactive yellow protein, a small, water-soluble blue-light absorbing photoreceptor protein from Ectothiorhodospira(Halorhodospira)[space]halophila has a structure with two hydrophobic cores, of which the main one houses its light-sensitive chromophore (p-coumaric acid), separated by a central [small beta]-sheet. This photoreceptor protein contains a single tryptophan residue (W119) that is situated at the interface between the central beta-sheet and its N-terminal cap. The fluorescence properties of W119 in the dark state pG (lambda(max)= 328 nm; Phi(fl)= 0.01; nearly pH-independent) are typical for a buried tryptophan in a hydrophobic environment with significant quenching by nearby amino acid residues. Signalling state formation leads to pH-dependent fluorescence changes: At pH values <6.5 the fluorescence emission increases, with a minor blue shift of the emission maximum. Above this pH, the emission maximum of the tryptophan shifts considerably to the red, whereas its total intensity decreases. These results further support the contention that signalling state formation in PYP leads to significant changes in the structure of this protein, even at sites that are at a considerable distance from the chromophore. The nature of these changes in pB, however, depend upon the pH imposed upon the protein: At slightly alkaline pH, which presumably is closest to the pH to which this protein is exposed in vivo, these changes lead to an exposure of the part of the central beta-sheet harbouring W119. At slightly acidic pH the polarity of the environment of W119 is hardly affected by the formation of the signalling state but the quenching of its fluorescence emission, possibly by nearby amino acids, is reduced. On the other hand, its accessibility for quenching by small molecules in the solution is enhanced at acidic and alkaline pH in the signalling state (pB) compared to the dark state (pG). This latter observation points towards a more flexible structure of the N-terminal cap, having a looser interaction with the central beta-sheet in pB. SN - 1474-905X UR - https://www.unboundmedicine.com/medline/citation/15170481/Tryptophan_fluorescence_monitors_structural_changes_accompanying_signalling_state_formation_in_the_photocycle_of_photoactive_yellow_protein_ L2 - https://doi.org/10.1039/b401600a DB - PRIME DP - Unbound Medicine ER -