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Solid-state NMR spectroscopy to probe photoactivation in canonical phytochromes.
- Source :
-
Photochemistry and photobiology [Photochem Photobiol] 2013 Mar-Apr; Vol. 89 (2), pp. 259-73. Date of Electronic Publication: 2013 Jan 25. - Publication Year :
- 2013
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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 chromophore-protein 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 Å. 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.<br /> (© 2013 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2013 The American Society of Photobiology.)
Details
- Language :
- English
- ISSN :
- 1751-1097
- Volume :
- 89
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Photochemistry and photobiology
- Publication Type :
- Academic Journal
- Accession number :
- 23216105
- Full Text :
- https://doi.org/10.1111/php.12029