The Solution Structure of a Transient Photoreceptor Intermediate: Δ25 Photoactive Yellow Protein

• Published in: Structure (London) 2005-07, Vol.13 (7), p.953-962
• Main Authors: Bernard, Cédric, Houben, Klaartje, Derix, Nocky M., Marks, David, van der Horst, Michael A., Hellingwerf, Klaas J., Boelens, Rolf, Kaptein, Robert, van Nuland, Nico A.J.
• Format: Article
• Language: English
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2005.04.017

The N-terminally truncated variant of photoactive yellow protein (Δ25-PYP) undergoes a very similar photocycle as the corresponding wild-type protein (WT-PYP), although the lifetime of its light-illuminated (pB) state is much longer. This has allowed determination of the structure of both its dark- (pG) as well as its pB-state in solution by nuclear magnetic resonance (NMR) spectroscopy. The pG structure shows a well-defined fold, similar to WT-PYP and the X-ray structure of the pG state of Δ25-PYP. In the long-lived photocycle intermediate pB, the central β sheet is still intact, as well as a small part of one α helix. The remainder of pB is unfolded and highly flexible, as evidenced by results from proton-deuterium exchange and NMR relaxation studies. Thus, the partially unfolded nature of the presumed signaling state of PYP in solution, as suggested previously, has now been structurally demonstrated.