Low-barrier hydrogen bond in photoactive yellow protein

Low-barrier hydrogen bonds (LBHBs) have been proposed to play roles in protein functions, including enzymatic catalysis and proton transfer. Transient formation of LBHBs is expected to stabilize specific reaction intermediates. However, based on experimental results and theoretical considerations, a...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2009-01, Vol.106 (2), p.440-444
Main Authors: Yamaguchi, Shigeo, Kamikubo, Hironari, Kurihara, Kazuo, Kuroki, Ryota, Niimura, Nobuo, Shimizu, Nobutaka, Yamazaki, Yoichi, Kataoka, Mikio
Format: Article
Language:English
Subjects:
Atoms
Bacterial Proteins - chemistry
Biological Sciences
Chromophores
Crystallography
Deuterium
Enzyme kinetics
Hydrogen
Hydrogen Bonding
Hydrogen bonds
Molecular Structure
Neutron Diffraction
Neutrons
Oxygen
Photoreceptors, Microbial - chemistry
Protein Conformation
Proteins
Protons
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Summary:Low-barrier hydrogen bonds (LBHBs) have been proposed to play roles in protein functions, including enzymatic catalysis and proton transfer. Transient formation of LBHBs is expected to stabilize specific reaction intermediates. However, based on experimental results and theoretical considerations, arguments against the importance of LBHB in proteins have been raised. The discrepancy is caused by the absence of direct identification of the hydrogen atom position. Here, we show by high-resolution neutron crystallography of photoactive yellow protein (PYP) that a LBHB exists in a protein, even in the ground state. We identified [almost equal to]87% (819/942) of the hydrogen positions in PYP and demonstrated that the hydrogen bond between the chromophore and E46 is a LBHB. This LBHB stabilizes an isolated electric charge buried in the hydrophobic environment of the protein interior. We propose that in the excited state the fast relaxation of the LBHB into a normal hydrogen bond is the trigger for photo-signal propagation to the protein moiety. These results give insights into the novel roles of LBHBs and the mechanism of the formation of LBHBs.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0811882106