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GTP-Dependent Regulation of CTP Synthase: Evolving Insights into Allosteric Activation and NH(3) Translocation

Cytidine-5′-triphosphate (CTP) synthase (CTPS) is the class I glutamine-dependent amidotransferase (GAT) that catalyzes the last step in the de novo biosynthesis of CTP. Glutamine hydrolysis is catalyzed in the GAT domain and the liberated ammonia is transferred via an intramolecular tunnel to the s...

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Autores principales: Bearne, Stephen L., Guo, Chen-Jun, Liu, Ji-Long
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9138612/
https://www.ncbi.nlm.nih.gov/pubmed/35625575
http://dx.doi.org/10.3390/biom12050647
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author Bearne, Stephen L.
Guo, Chen-Jun
Liu, Ji-Long
author_facet Bearne, Stephen L.
Guo, Chen-Jun
Liu, Ji-Long
author_sort Bearne, Stephen L.
collection PubMed
description Cytidine-5′-triphosphate (CTP) synthase (CTPS) is the class I glutamine-dependent amidotransferase (GAT) that catalyzes the last step in the de novo biosynthesis of CTP. Glutamine hydrolysis is catalyzed in the GAT domain and the liberated ammonia is transferred via an intramolecular tunnel to the synthase domain where the ATP-dependent amination of UTP occurs to form CTP. CTPS is unique among the glutamine-dependent amidotransferases, requiring an allosteric effector (GTP) to activate the GAT domain for efficient glutamine hydrolysis. Recently, the first cryo-electron microscopy structure of Drosophila CTPS was solved with bound ATP, UTP, and, notably, GTP, as well as the covalent adduct with 6-diazo-5-oxo-l-norleucine. This structural information, along with the numerous site-directed mutagenesis, kinetics, and structural studies conducted over the past 50 years, provide more detailed insights into the elaborate conformational changes that accompany GTP binding at the GAT domain and their contribution to catalysis. Interactions between GTP and the L2 loop, the L4 loop from an adjacent protomer, the L11 lid, and the L13 loop (or unique flexible “wing” region), induce conformational changes that promote the hydrolysis of glutamine at the GAT domain; however, direct experimental evidence on the specific mechanism by which these conformational changes facilitate catalysis at the GAT domain is still lacking. Significantly, the conformational changes induced by GTP binding also affect the assembly and maintenance of the NH(3) tunnel. Hence, in addition to promoting glutamine hydrolysis, the allosteric effector plays an important role in coordinating the reactions catalyzed by the GAT and synthase domains of CTPS.
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spelling pubmed-91386122022-05-28 GTP-Dependent Regulation of CTP Synthase: Evolving Insights into Allosteric Activation and NH(3) Translocation Bearne, Stephen L. Guo, Chen-Jun Liu, Ji-Long Biomolecules Review Cytidine-5′-triphosphate (CTP) synthase (CTPS) is the class I glutamine-dependent amidotransferase (GAT) that catalyzes the last step in the de novo biosynthesis of CTP. Glutamine hydrolysis is catalyzed in the GAT domain and the liberated ammonia is transferred via an intramolecular tunnel to the synthase domain where the ATP-dependent amination of UTP occurs to form CTP. CTPS is unique among the glutamine-dependent amidotransferases, requiring an allosteric effector (GTP) to activate the GAT domain for efficient glutamine hydrolysis. Recently, the first cryo-electron microscopy structure of Drosophila CTPS was solved with bound ATP, UTP, and, notably, GTP, as well as the covalent adduct with 6-diazo-5-oxo-l-norleucine. This structural information, along with the numerous site-directed mutagenesis, kinetics, and structural studies conducted over the past 50 years, provide more detailed insights into the elaborate conformational changes that accompany GTP binding at the GAT domain and their contribution to catalysis. Interactions between GTP and the L2 loop, the L4 loop from an adjacent protomer, the L11 lid, and the L13 loop (or unique flexible “wing” region), induce conformational changes that promote the hydrolysis of glutamine at the GAT domain; however, direct experimental evidence on the specific mechanism by which these conformational changes facilitate catalysis at the GAT domain is still lacking. Significantly, the conformational changes induced by GTP binding also affect the assembly and maintenance of the NH(3) tunnel. Hence, in addition to promoting glutamine hydrolysis, the allosteric effector plays an important role in coordinating the reactions catalyzed by the GAT and synthase domains of CTPS. MDPI 2022-04-29 /pmc/articles/PMC9138612/ /pubmed/35625575 http://dx.doi.org/10.3390/biom12050647 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Review
Bearne, Stephen L.
Guo, Chen-Jun
Liu, Ji-Long
GTP-Dependent Regulation of CTP Synthase: Evolving Insights into Allosteric Activation and NH(3) Translocation
title GTP-Dependent Regulation of CTP Synthase: Evolving Insights into Allosteric Activation and NH(3) Translocation
title_full GTP-Dependent Regulation of CTP Synthase: Evolving Insights into Allosteric Activation and NH(3) Translocation
title_fullStr GTP-Dependent Regulation of CTP Synthase: Evolving Insights into Allosteric Activation and NH(3) Translocation
title_full_unstemmed GTP-Dependent Regulation of CTP Synthase: Evolving Insights into Allosteric Activation and NH(3) Translocation
title_short GTP-Dependent Regulation of CTP Synthase: Evolving Insights into Allosteric Activation and NH(3) Translocation
title_sort gtp-dependent regulation of ctp synthase: evolving insights into allosteric activation and nh(3) translocation
topic Review
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9138612/
https://www.ncbi.nlm.nih.gov/pubmed/35625575
http://dx.doi.org/10.3390/biom12050647
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