Neutron and X-ray structural studies of short hydrogen bonds in photoactive yellow protein (PYP)

• Published in: Acta crystallographica. Section D, Biological crystallography. Vol. 63; no. 11; pp. 1178 - 1184
• Main Authors: Fisher, S. Z., Anderson, S., Henning, R., Moffat, K., Langan, P., Thiyagarajan, P., Schultz, A. J.
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England Blackwell Publishing Ltd 01.11.2007
• Subjects: Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Binding Sites; Coumaric Acids - chemistry; Crystallization; Crystallography, X-Ray; Deuterium Oxide - chemistry; Halorhodospira halophila - chemistry; Halorhodospira halophila - genetics; Hydrogen Bonding; hydrogen bonds; Models, Molecular; Neutron Diffraction; photoactive yellow protein; Photoreceptors, Microbial - chemistry; Photoreceptors, Microbial - genetics; Propionates; Protons; Recombinant Proteins - chemistry
• ISSN: 1399-0047; 0907-4449; 1399-0047
• DOI: 10.1107/S0907444907047646

Photoactive yellow protein (PYP) from Halorhodospira halophila is a soluble 14 kDa blue‐light photoreceptor. It absorbs light via its para‐coumaric acid chromophore (pCA), which is covalently attached to Cys69 and is believed to be involved in the negative phototactic response of the organism to blue light. The complete structure (including H atoms) of PYP has been determined in D2O‐soaked crystals through the application of joint X‐ray (1.1 Å) and neutron (2.5 Å) structure refinement in combination with cross‐validated maximum‐likelihood simulated annealing. The resulting XN structure reveals that the phenolate O atom of pCA accepts deuterons from Glu46 Oɛ2 and Tyr42 Oη in two unusually short hydrogen bonds. This arrangement is stabilized by the donation of a deuteron from Thr50 Oγ1 to Tyr42 Oη. However, the deuteron position between pCA and Tyr42 is only partially occupied. Thus, this atom may also interact with Thr50, possibly being disordered or fluctuating between the two bonds.