4ZF4

Crystal structure of Green Fluorescent Protein (GFP); S65T, Y66(Cl1Y), H148D; circular permutant (50-51)

Summary for 4ZF4

• Entry DOI: 10.2210/pdb4zf4/pdb
• Related: 4ZF3 4ZF5
• Descriptor: Green fluorescent protein (2 entities in total)
• Functional Keywords: fluorescent protein
• Biological source: Aequorea victoria (Jellyfish); More
• Total number of polymer chains: 2
• Total formula weight: 56451.83

Authors

Oltrogge, L.M.,Boxer, S.G. (deposition date: 2015-04-21, release date: 2015-06-10, Last modification date: 2023-11-15)

Primary citation

Oltrogge, L.M.,Boxer, S.G.
Short Hydrogen Bonds and Proton Delocalization in Green Fluorescent Protein (GFP).
Acs Cent.Sci., 1:148-156, 2015

PubMed Abstract: Short hydrogen bonds and specifically low-barrier hydrogen bonds (LBHBs) have been the focus of much attention and controversy for their possible role in enzymatic catalysis. The green fluorescent protein (GFP) mutant S65T, H148D has been found to form a very short hydrogen bond between Asp148 and the chromophore resulting in significant spectral perturbations. Leveraging the unique autocatalytically formed chromophore and its sensitivity to this interaction we explore the consequences of proton affinity matching across this putative LBHB. Through the use of noncanonical amino acids introduced through nonsense suppression or global incorporation, we systematically modify the acidity of the GFP chromophore with halogen substituents. X-ray crystal structures indicated that the length of the interaction with Asp148 is unchanged at ∼2.45 Å while the absorbance spectra demonstrate an unprecedented degree of color tuning with increasing acidity. We utilized spectral isotope effects, isotope fractionation factors, and a simple 1D model of the hydrogen bond coordinate in order to gain insight into the potential energy surface and particularly the role that proton delocalization may play in this putative short hydrogen bond. The data and model suggest that even with the short donor-acceptor distance (∼2.45 Å) and near perfect affinity matching there is not a LBHB, that is, the barrier to proton transfer exceeds the H zero-point energy.

PubMed: 27162964
DOI: 10.1021/acscentsci.5b00160

Experimental method

X-RAY DIFFRACTION (1.823 Å)