5ajg
From Proteopedia
Structure of Infrared Fluorescent Protein IFP1.4 AT 1.11 Angstrom resolution
Structural highlights
Function[BPHY_DEIRA] Photoreceptor which exists in two forms that are reversibly interconvertible by light: the R form that absorbs maximally in the red region of the spectrum and the FR form that absorbs maximally in the far-red region. Has also a slight blue shift for the far-red maximum. Could also absorb green light. May participate in regulating pigment synthesis like the carotenoid deinoxanthin which could protect the bacterium from intense visible light. Publication Abstract from PubMedUsing X-ray crystallography, continuum electrostatic calculations, and molecular dynamics simulations, we have studied the structure, protonation behavior, and dynamics of the biliverdin chromophore and its molecular environment in a series of genetically engineered infrared fluorescent proteins (IFPs) based on the chromophore-binding domain of the Deinococcus radiodurans bacteriophytochrome. Our study suggests that the experimentally observed enhancement of fluorescent properties results from the improved rigidity and planarity of the biliverdin chromophore, in particular of the first two pyrrole rings neighboring the covalent linkage to the protein. We propose that the increases in the levels of both motion and bending of the chromophore out of planarity favor the decrease in fluorescence. The chromophore-binding pocket in some of the studied proteins, in particular the weakly fluorescent parent protein, is shown to be readily accessible to water molecules from the solvent. These waters entering the chromophore region form hydrogen bond networks that affect the otherwise planar conformation of the first three rings of the chromophore. On the basis of our simulations, the enhancement of fluorescence in IFPs can be achieved either by reducing the mobility of water molecules in the vicinity of the chromophore or by limiting the interactions of the nearby protein residues with the chromophore. Finally, simulations performed at both low and neutral pH values highlight differences in the dynamics of the chromophore and shed light on the mechanism of fluorescence loss at low pH. Structural Determinants of Improved Fluorescence in a Family of Bacteriophytochrome-Based Infrared Fluorescent Proteins: Insights from Continuum Electrostatic Calculations and Molecular Dynamics Simulations.,Feliks M, Lafaye C, Shu X, Royant A, Field M Biochemistry. 2016 Aug 9;55(31):4263-74. doi: 10.1021/acs.biochem.6b00295. Epub, 2016 Jul 29. PMID:27471775[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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