Song, Chen, Psakis, Georgios, Lang, Christina, Mailliet, Jo, Zaanen, Jan, Gaertner, Wolfgang, Hughes, Jon and Matysik, Joerg (2011) On the collective nature of phytochrome photoactivation. Biochemistry, 50 (51). pp. 10987-10989. ISSN 0006-2960

The red/far-red-sensing biological photoreceptor phytochrome is a paradigmatic two-state signaling system. The two thermally stable states are interconverted via a photoreaction of the covalently bound tetrapyrrole chromophore. Applying recently developed solid-state nuclear magnetic resonance, we study both the chromophore and its protein pocket in the Pr (red-absorbing) and Pfr (far-red-absorbing) states. The observations show that the phototransformation combines local chemical reactions with a mesoscopic transition of order. Both the chromophore and its binding pocket are quasi-liquid and disordered in Pr, yet quasi-solid and ordered in Pfr. Possible biochemical implications are discussed.

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