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Structure of the Biliverdin Cofactor in the Pfr State of Bathy and Prototypical Phytochromes
Zitatschlüssel Salewski2013
Autor Salewski, Johannes and Escobar, Francisco Velazquez and Kaminski, Steve and von Stetten, David and Keidel, Anke and Rippers, Yvonne and Michael, Norbert and Scheerer, Patrick and Piwowarski, Patrick and Bartl, Franz and Frankenberg-Dinkel, Nicole and Ringsdorf, Simone and Gaertner, Wolfgang and Lamparter, Tilman and Mroginski, Maria Andrea and Hildebrandt, Peter
Seiten 16800–16814
Jahr 2013
Journal Journal of Biological Chemistry
Jahrgang 288
Nummer 23
Monat jun
Zusammenfassung Phytochromes act as photoswitches between the red-and farred absorbing parent states of phytochromes (Pr and Pfr). Plant phytochromes display an additional thermal conversion route from the physiologically active Pfr to Pr. The same reaction pattern is found in prototypical biliverdin-binding bacteriophytochromes in contrast to the reverse thermal transformation in bathy bacteriophytochromes. However, the molecular origin of the different thermal stabilities of the Pfr states in prototypical and bathy bacteriophytochromes is not known. Weanalyzed the structures of the chromophore binding pockets in the Pfr states of various bathy and prototypical biliverdin-binding phytochromes using a combined spectroscopic-theoretical approach. For the Pfr state of the bathy phytochrome from Pseudomonas aeruginosa, the very good agreement between calculated and experimental Raman spectra of the biliverdin cofactor is in line with important conclusions of previous crystallographic analyses, particularly the ZZEssa configuration of the chromophore and its mode of covalent attachment to the protein. The highly homogeneous chromophore conformation seems to be a unique property of the Pfr states of bathy phytochromes. This is in sharp contrast to the Pfr states of prototypical phytochromes that display conformational equilibria between two sub-states exhibiting small structural differences at the terminal methine bridges A-B and C-D. These differences may mainly root in the interactions of the cofactor with the highly conserved Asp-194 that occur via its carboxylate function in bathy phytochromes. The weaker interactions via the carbonyl function in prototypical phytochromes may lead to a higher structural flexibility of the chromophore pocket opening a reaction channel for the thermal (ZZE -> ZZZ) Pfr to Pr back-conversion.
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