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Autori: Cornilescu, G., Ulijasz A.T., Cornilescu, C.C., Zhang, J., Rivera, M., Markley, J.L., Vierstra, R.D.
Editorial: Nature, 463, p.250-254, 2010.
Phytochromes are a collection of bilin-containing photoreceptors that regulate numerous photoresponses in plants and microorganisms through their ability to photointerconvert between a red light-absorbing, ground state Pr and a far-red light-absorbing, photoactivated state Pfr. While the structures of several phytochromes as Pr have been determined, little is known about the structure of Pfr and how it initiates signaling. Here, we describe the three-dimensional solution structure of the bilin-binding domain as Pfr using the cyanobacterial phytochrome from Synechococcus OSB’. Contrary to predictions, light-induced rotation of the A but not the D pyrrole ring is the primary motion of the chromophore during photoconversion. Subsequent rearrangements within the protein then affect intra- and interdomain contact sites within the phytochrome dimer. From our models, we propose that phytochromes act by propagating reversible light-driven conformational changes in the bilin to altered contacts between the adjacent output domains, which in most phytochromes direct differential phosphotransfer.
Cuvinte cheie: Phytochrome, NMR, photoreceptor, bilin, PCB, phycocyanobilin