Journal article

Publication year: 2013

Pages: 259-273

Journal: Photochemistry and Photobiology

Volume number: 89

Issue number: 2

ISSN: 0031-8655

DOI Link: https://doi.org/10.1111/php.12029

Publisher: Wiley

Abstract: 
The photoreceptor phytochrome switches photochromically between two thermally stable states called Pr and Pfr. Here, we summarize recent solid-state magic-angle spinning (MAS) NMR work on this conversion process and interpret the functional mechanism in terms of a nano-machine. The process is initiated by a double-bond photoisomerization of the open-chain tetrapyrrole chromophore at the methine bridge connecting pyrrole rings C and D. The Pr-state chromophore and its surrounding pocket in canonical cyanobacterial and plant phytochromes has significantly less order, tends to form isoforms and is soft. Conversely, Pfr shows significantly harder chromophoreprotein interactions, a well-defined protonic and charge distribution with a clear classical counterion for the positively charged tetrapyrrole system. The soft-to-hard/disorder-to-order transition involves the chromophore and its protein surroundings within a sphere of at least 5.5 angstrom. The relevance of this collective event for signaling is discussed. Measurement of the intermediates during the Pfr Pr back-reaction provides insight into the well-adjusted mechanics of a two-step transformation. As both Pr Pfr and Pfr Pr reaction pathways are different in ground and excited states, a photochemically controlled hyper-landscape is proposed allowing for ratchet-type reaction dynamics regulating signaling activity.

Harvard Citation style: Song, C., Rohmer, T., Tiersch, M., Zaanen, J., Hughes, J. and Matysik, J. (2013) Solid-State NMR Spectroscopy to Probe Photoactivation in Canonical Phytochromes, Photochemistry and Photobiology, 89(2), pp. 259-273. https://doi.org/10.1111/php.12029

APA Citation style: Song, C., Rohmer, T., Tiersch, M., Zaanen, J., Hughes, J., & Matysik, J. (2013). Solid-State NMR Spectroscopy to Probe Photoactivation in Canonical Phytochromes. Photochemistry and Photobiology. 89(2), 259-273. https://doi.org/10.1111/php.12029