scholarly journals A hybrid approach reveals the allosteric regulation of GTP cyclohydrolase I

2020 ◽  
Vol 117 (50) ◽  
pp. 31838-31849
Author(s):  
Rebecca Ebenhoch ◽  
Simone Prinz ◽  
Susann Kaltwasser ◽  
Deryck J. Mills ◽  
Robert Meinecke ◽  
...  
Keyword(s):  
Crystal Packing ◽  
Substrate Binding ◽  
Regulatory Protein ◽  
Allosteric Regulation ◽  
Hybrid Approach ◽  
Site Directed Mutagenesis ◽  
Gtp Cyclohydrolase I ◽  
Gtp Cyclohydrolase ◽  
X Ray ◽  
X Ray Crystallography

Guanosine triphosphate (GTP) cyclohydrolase I (GCH1) catalyzes the conversion of GTP to dihydroneopterin triphosphate (H2NTP), the initiating step in the biosynthesis of tetrahydrobiopterin (BH4). Besides other roles, BH4 functions as cofactor in neurotransmitter biosynthesis. The BH4 biosynthetic pathway and GCH1 have been identified as promising targets to treat pain disorders in patients. The function of mammalian GCH1s is regulated by a metabolic sensing mechanism involving a regulator protein, GCH1 feedback regulatory protein (GFRP). GFRP binds to GCH1 to form inhibited or activated complexes dependent on availability of cofactor ligands, BH4 and phenylalanine, respectively. We determined high-resolution structures of human GCH1−GFRP complexes by cryoelectron microscopy (cryo-EM). Cryo-EM revealed structural flexibility of specific and relevant surface lining loops, which previously was not detected by X-ray crystallography due to crystal packing effects. Further, we studied allosteric regulation of isolated GCH1 by X-ray crystallography. Using the combined structural information, we are able to obtain a comprehensive picture of the mechanism of allosteric regulation. Local rearrangements in the allosteric pocket upon BH4 binding result in drastic changes in the quaternary structure of the enzyme, leading to a more compact, tense form of the inhibited protein, and translocate to the active site, leading to an open, more flexible structure of its surroundings. Inhibition of the enzymatic activity is not a result of hindrance of substrate binding, but rather a consequence of accelerated substrate binding kinetics as shown by saturation transfer difference NMR (STD-NMR) and site-directed mutagenesis. We propose a dissociation rate controlled mechanism of allosteric, noncompetitive inhibition.

Elucidation of Crystal Packing by X-ray Diffraction and Freeze-etching Electron Microscopy. Studies on GTP Cyclohydrolase I ofEscherichia coli

1995 ◽  
Vol 253 (1) ◽  
pp. 208-218 ◽  
Author(s):  
Winfried Meining ◽  
Adelbert Bacher ◽  
Luis Bachmann ◽  
Cornelia Schmid ◽  
Sevil Weinkauf ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Crystal Packing ◽  
Ofescherichia Coli ◽  
X Ray Diffraction ◽  
Gtp Cyclohydrolase I ◽  
Gtp Cyclohydrolase ◽  
X Ray ◽  
Freeze Etching

Substituent position effect on the crystal structures of N-phenyl-2-phthalimidoethanesulfonamide derivatives

2018 ◽  
Vol 74 (1) ◽  
pp. 31-36
Author(s):  
Resul Sevinçek ◽  
Duygu Barut Celepci ◽  
Serap Köktaş Koca ◽  
Özlem Akgül ◽  
Muittin Aygün
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Packing ◽  
Biological Activities ◽  
Position Effect ◽  
Intermolecular Hydrogen Bond ◽  
X Ray ◽  
Space Groups ◽  
X Ray Crystallography ◽  
Hydrogen Bond Interactions ◽  
The Impact

In order to determine the impact of different substituents and their positions on intermolecular interactions and ultimately on the crystal packing, unsubstituted N-phenyl-2-phthalimidoethanesulfonamide, C16H14N2O4S, (I), and the N-(4-nitrophenyl)-, C16H13N3O6S, (II), N-(4-methoxyphenyl)-, C16H16N3O6S, (III), and N-(2-ethylphenyl)-, as the monohydrate, C18H18N2O4S·H2O, (IV), derivatives have been characterized by single-crystal X-ray crystallography. Sulfonamides (I) and (II) have triclinic crystal systems, while (III) and (IV) are monoclinic. Although the molecules differ from each other only with respect to small substituents and their positions, they crystallized in different space groups as a result of differing intra- and intermolecular hydrogen-bond interactions. The structures of (I), (II) and (III) are stabilized by intermolecular N—H...O and C—H...O hydrogen bonds, while that of (IV) is stabilized by intermolecular O—H...O and C—H...O hydrogen bonds. All four structures are of interest with respect to their biological activities and have been studied as part of a program to develop anticonvulsant drugs for the treatment of epilepsy.

scholarly journals Expansion of Substrate Specificity and Catalytic Mechanism of Azoreductase by X-ray Crystallography and Site-directed Mutagenesis

2008 ◽  
Vol 283 (20) ◽  
pp. 13889-13896 ◽  
Author(s):  
Kosuke Ito ◽  
Masayuki Nakanishi ◽  
Woo-Cheol Lee ◽  
Yuehua Zhi ◽  
Hiroshi Sasaki ◽  
...  
Keyword(s):  
Substrate Specificity ◽  
Catalytic Mechanism ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
X Ray ◽  
X Ray Crystallography

scholarly journals Crystal Packing and Supramolecular Motifs in Four Phenoxyalkanoic Acid Herbicides—Low-Temperature Redeterminations

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Lesław Sieroń ◽  
Joanna Kobyłecka ◽  
Anna Turek
Keyword(s):  
Low Temperature ◽  
Propionic Acid ◽  
Crystal Packing ◽  
Dichlorophenoxyacetic Acid ◽  
X Ray ◽  
Π Interactions ◽  
X Ray Crystallography ◽  
Supramolecular Motifs ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
Acid Herbicides

A low-temperature redetermination by X-ray crystallography of four phenoxyalkanoic acid herbicides, 4-chloro-2-methylphenoxyacetic acid (MCPA), rac-2-(4-chloro-2-methylphenoxy)propionic acid (MCPP), 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4-dichlorophenoxybutyric acid (2,4-DB), allowed the supramolecular structures of these compounds to be precisely described in terms of C⋯O/C–H⋯π interactions. The geometric parameters of the redetermined structures agree with those previously reported, but with improved precision.

scholarly journals Tetrahydrobiopterin biosynthesis, regeneration and functions

2000 ◽  
Vol 347 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Beat THÖNY ◽  
Günter AUERBACH ◽  
Nenad BLAU
Keyword(s):  
De Novo ◽  
Recombinant Expression ◽  
Regulatory Protein ◽  
Cellular Level ◽  
No Synthase ◽  
Gtp Cyclohydrolase I ◽  
Gtp Cyclohydrolase ◽  
Nmr Studies ◽  
Sepiapterin Reductase ◽  
Mammalian Cell Lines

Tetrahydrobiopterin (BH4) cofactor is essential for various processes, and is present in probably every cell or tissue of higher organisms. BH4 is required for various enzyme activities, and for less defined functions at the cellular level. The pathway for the de novo biosynthesis of BH4 from GTP involves GTP cyclohydrolase I, 6-pyruvoyl-tetrahydropterin synthase and sepiapterin reductase. Cofactor regeneration requires pterin-4a-carbinolamine dehydratase and dihydropteridine reductase. Based on gene cloning, recombinant expression, mutagenesis studies, structural analysis of crystals and NMR studies, reaction mechanisms for the biosynthetic and recycling enzymes were proposed. With regard to the regulation of cofactor biosynthesis, the major controlling point is GTP cyclohydrolase I, the expression of which may be under the control of cytokine induction. In the liver at least, activity is inhibited by BH4, but stimulated by phenylalanine through the GTP cyclohydrolase I feedback regulatory protein. The enzymes that depend on BH4 are the phenylalanine, tyrosine and tryptophan hydroxylases, the latter two being the rate-limiting enzymes for catecholamine and 5-hydroxytryptamine (serotonin) biosynthesis, all NO synthase isoforms and the glyceryl-ether mono-oxygenase. On a cellular level, BH4 has been found to be a growth or proliferation factor for Crithidia fasciculata, haemopoietic cells and various mammalian cell lines. In the nervous system, BH4 is a self-protecting factor for NO, or a general neuroprotecting factor via the NO synthase pathway, and has neurotransmitter-releasing function. With regard to human disease, BH4 deficiency due to autosomal recessive mutations in all enzymes (except sepiapterin reductase) have been described as a cause of hyperphenylalaninaemia. Furthermore, several neurological diseases, including Dopa-responsive dystonia, but also Alzheimer's disease, Parkinson's disease, autism and depression, have been suggested to be a consequence of restricted cofactor availability.

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