(1) Bijvoet Center, Utrecht University, Padualaan 8, 3584 CH Utrecht, The
Netherlands
(2) Slater Institute, University of Amsterdam, Nieuwe Achtergracht 127,
1018 WS Amsterdam, The Netherlands
(3) Leiden Institute of Chemistry, Leiden University, 2300 RA Leiden, The
Netherlands
(4) Dept. of Microbiol. & Molec. Genetics, University of Texas, Houston, USA
The three-dimensional solution structure of the dark state of Photoactive Yellow Protein (PYP) has been determined by nuclear magnetic resonance (NMR) spectroscopy.
PYP has a molecular weight of 14 kDa and shows strong absorbance at 446 nm, which initiates a kinetic cycle of thermal decays [Meyer, 1991]. PYP has first been isolated from E. halophila and the repellent response of E. halophila towards blue light shows the same wavelength dependence as the absorption spectrum of PYP. This suggests that PYP functions as a photoreceptor in the negative phototaxis of the cell [Sprenger, 1991]. The analyses of the structure of the chromophore elicited a new cofactor: a p-coumaric acid molecule bound to the only cysteine via a thiol ester bond. With this finding, PYP is not only the first identified eubacterial photosensory protein, but also the first protein containing a thiol ester - linked cofactor.
The initial crystal structure of PYP at 2.4Å resolution [McRee, 1989] showed a beta-sheet conformation, consisting of two perpendicular, anti-parallel beta-sheets that form a beta-clam structure. The second crystallographic structure at 1.4Å resolution shows an beta/alpha fold similar to distinct parts of the signal transduction protein profilin and the SH2 domain [Borgstahl, 1995] and consists of a central, six-stranded, anti-parallel beta-sheet, flanked on both sides by alpha-helical loop regions.
Similar to the latest crystal structure the solution structure, presented here, shows a six-stranded, anti-parallel beta-sheet and alpha-helical regions. The internal mobility of the nano second time scale is characterized for specific regions in PYP using 15N NMR relaxation measurements.
References:
G. E. O. Borgstahl, W. R. Williams, E. D. Getzoff, Biochemistry 34,
6278 - 6287, 1995
D. E. McRee, J. A. Tainer, T. E. Meyer, J. van Beeumen, M. A.
Cusanovich, E. D. Getzoff, Proc.Natl.Acad.Sci.USA 86, 6533 - 6537, 1989
T. E. Meyer, E. Yakali, M. A. Cusanovich, G. Tollin, Biochemistry 26,
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T. E. Meyer, G. Tollin, T. P. Causgrove, P. Cheng, R. E. Blankenship,
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W. W. Sprenger, W. D. Hoff, J. P. Armitage, K. J. Hellingwerf, J.
Bacteriol. 175, 3096 - 3104, 1993