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Perturbation of Short Hydrogen Bonds in Photoactive Yellow Protein via Noncanonical Amino Acid Incorporation
- Source :
- J Phys Chem B
- Publication Year :
- 2019
- Publisher :
- American Chemical Society (ACS), 2019.
-
Abstract
- Photoactive yellow protein (PYP) is a small photoreceptor protein that has two unusually short hydrogen bonds between the deprotonated p-coumaric acid chromophore and two amino acids, a tyrosine and a glutamic acid. This has led to considerable debate as to whether the glutamic acid-chromophore hydrogen bond is a low barrier hydrogen bond, with conflicting results in the literature. We have modified the pK(a) of the tyrosine by amber suppression and of the chromophore by chemical substitution. X-ray crystal structures of these modified proteins are nearly identical to the wild-type protein, so the heavy atom distance between proton donor and acceptor is maintained, even though these modifications change the relative proton affinity between donor and acceptor. Despite a considerable change in relative proton affinity, the NMR chemical shifts of the hydrogen-bonded protons are only moderately affected. QM/MM calculations were used to explore the protons’ potential energy surface and connect the calculated proton position with empirically measured proton chemical shifts. The results are inconsistent with a low barrier hydrogen bond but in all cases are consistent with a localized proton, suggesting an ionic hydrogen bond rather than a low barrier hydrogen bond.
- Subjects :
- Models, Molecular
Proton
Hydrogen bond
Chemistry
Low-barrier hydrogen bond
Ionic bonding
Hydrogen Bonding
Chromophore
Crystallography, X-Ray
Photochemical Processes
Photoreceptors, Microbial
Acceptor
Article
Surfaces, Coatings and Films
Crystallography
Deprotonation
Bacterial Proteins
Materials Chemistry
Proton affinity
Amino Acids
Physical and Theoretical Chemistry
Nuclear Magnetic Resonance, Biomolecular
Subjects
Details
- ISSN :
- 15205207 and 15206106
- Volume :
- 123
- Database :
- OpenAIRE
- Journal :
- The Journal of Physical Chemistry B
- Accession number :
- edsair.doi.dedup.....385687533440676106995c2a7fb080e0