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Xu G, Ma J, Fang Q, Peng Q, Jiao X, Hu W, Zhao Q, Kong Y, Liu F, Shi X, Tang DJ, Tang JL, Ming Z. Structural insights into Xanthomonas campestris pv. campestris NAD + biosynthesis via the NAM salvage pathway. Commun Biol 2024; 7:255. [PMID: 38429435 PMCID: PMC10907753 DOI: 10.1038/s42003-024-05921-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 02/15/2024] [Indexed: 03/03/2024] Open
Abstract
Nicotinamide phosphoribosyltransferase (NAMPT) plays an important role in the biosynthesis of nicotinamide adenine dinucleotide (NAD+) via the nicotinamide (NAM) salvage pathway. While the structural biochemistry of eukaryote NAMPT has been well studied, the catalysis mechanism of prokaryote NAMPT at the molecular level remains largely unclear. Here, we demonstrated the NAMPT-mediated salvage pathway is functional in the Gram-negative phytopathogenic bacterium Xanthomonas campestris pv. campestris (Xcc) for the synthesis of NAD+, and the enzyme activity of NAMPT in this bacterium is significantly higher than that of human NAMPT in vitro. Our structural analyses of Xcc NAMPT, both in isolation and in complex with either the substrate NAM or the product nicotinamide mononucleotide (NMN), uncovered significant details of substrate recognition. Specifically, we revealed the presence of a NAM binding tunnel that connects the active site, and this tunnel is essential for both catalysis and inhibitor binding. We further demonstrated that NAM binding in the tunnel has a positive cooperative effect with NAM binding in the catalytic site. Additionally, we discovered that phosphorylation of the His residue at position 229 enhances the substrate binding affinity of Xcc NAMPT and is important for its catalytic activity. This work reveals the importance of NAMPT in bacterial NAD+ synthesis and provides insights into the substrate recognition and the catalytic mechanism of bacterial type II phosphoribosyltransferases.
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Affiliation(s)
- Guolyu Xu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Jinxue Ma
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Qi Fang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Qiong Peng
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Xi Jiao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Wei Hu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Qiaoqiao Zhao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Yanqiong Kong
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Fenmei Liu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Xueqi Shi
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Dong-Jie Tang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China
| | - Ji-Liang Tang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China.
| | - Zhenhua Ming
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530004, P. R. China.
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2
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Zhou Z, Yang X, Huang T, Zheng J, Deng Z, Dai S, Lin S. Bifunctional NadC Homologue PyrZ Catalyzes Nicotinic Acid Formation in Pyridomycin Biosynthesis. ACS Chem Biol 2023; 18:141-150. [PMID: 36517246 DOI: 10.1021/acschembio.2c00773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Pyridomycin is a potent antimycobacterial natural product by specifically inhibiting InhA, a clinically validated antituberculosis drug discovery target. Pyridyl moieties of pyridomycin play an essential role in inhibiting InhA by occupying the reduced form of the nicotinamide adenine dinucleotide (NADH) cofactor binding site. Herein, we biochemically characterize PyrZ that is a multifunctional NadC homologue and catalyzes the successive formation, dephosphorylation, and ribose hydrolysis of nicotinic acid mononucleotide (NAMN) to generate nicotinic acid (NA), a biosynthetic precursor for the pyridyl moiety of pyridomycin. Crystal structures of PyrZ in complex with substrate quinolinic acid (QA) and the final product NA revealed a specific salt bridge formed between K184 and the C3-carboxyl group of QA. This interaction positions QA for accepting the phosphoribosyl group to generate NAMN, retains NAMN within the active site, and mediates its translocation to nucleophile D296 for dephosphorylation. Combining kinetic and thermodynamic analysis with site-directed mutagenesis, the catalytic mechanism of PyrZ dephosphorylation was proposed. Our study discovered an alternative and concise NA biosynthetic pathway involving a unique multifunctional enzyme.
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Affiliation(s)
- Zihua Zhou
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Xu Yang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Tingting Huang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Jianting Zheng
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Zixin Deng
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Shaobo Dai
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Shuangjun Lin
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory on Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.,Frontiers Science Center for Transformative Molecules, Shanghai Jiao Tong University, Shanghai 200240, China
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3
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Odoh CK, Guo X, Arnone JT, Wang X, Zhao ZK. The role of NAD and NAD precursors on longevity and lifespan modulation in the budding yeast, Saccharomyces cerevisiae. Biogerontology 2022; 23:169-199. [PMID: 35260986 PMCID: PMC8904166 DOI: 10.1007/s10522-022-09958-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 02/16/2022] [Indexed: 11/26/2022]
Abstract
Molecular causes of aging and longevity interventions have witnessed an upsurge in the last decade. The resurgent interests in the application of small molecules as potential geroprotectors and/or pharmacogenomics point to nicotinamide adenine dinucleotide (NAD) and its precursors, nicotinamide riboside, nicotinamide mononucleotide, nicotinamide, and nicotinic acid as potentially intriguing molecules. Upon supplementation, these compounds have shown to ameliorate aging related conditions and possibly prevent death in model organisms. Besides being a molecule essential in all living cells, our understanding of the mechanism of NAD metabolism and its regulation remain incomplete owing to its omnipresent nature. Here we discuss recent advances and techniques in the study of chronological lifespan (CLS) and replicative lifespan (RLS) in the model unicellular organism Saccharomyces cerevisiae. We then follow with the mechanism and biology of NAD precursors and their roles in aging and longevity. Finally, we review potential biotechnological applications through engineering of microbial lifespan, and laid perspective on the promising candidature of alternative redox compounds for extending lifespan.
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Affiliation(s)
- Chuks Kenneth Odoh
- Laboratory of Biotechnology, Dalian Institute of Chemical Physics, CAS, 457 Zhongshan Rd, Dalian, 116023, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Xiaojia Guo
- Laboratory of Biotechnology, Dalian Institute of Chemical Physics, CAS, 457 Zhongshan Rd, Dalian, 116023, China
- Dalian Key Laboratory of Energy Biotechnology, Dalian Institute of Chemical Physics, CAS, 457 Zhongshan Rd, Dalian, 116023, China
| | - James T Arnone
- Department of Biology, William Paterson University, Wayne, NJ, 07470, USA
| | - Xueying Wang
- Laboratory of Biotechnology, Dalian Institute of Chemical Physics, CAS, 457 Zhongshan Rd, Dalian, 116023, China
- Dalian Key Laboratory of Energy Biotechnology, Dalian Institute of Chemical Physics, CAS, 457 Zhongshan Rd, Dalian, 116023, China
| | - Zongbao K Zhao
- Laboratory of Biotechnology, Dalian Institute of Chemical Physics, CAS, 457 Zhongshan Rd, Dalian, 116023, China.
- Dalian Key Laboratory of Energy Biotechnology, Dalian Institute of Chemical Physics, CAS, 457 Zhongshan Rd, Dalian, 116023, China.
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4
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Evans GL, Furkert DP, Abermil N, Kundu P, de Lange KM, Parker EJ, Brimble MA, Baker EN, Lott JS. Anthranilate phosphoribosyltransferase: Binding determinants for 5'-phospho-alpha-d-ribosyl-1'-pyrophosphate (PRPP) and the implications for inhibitor design. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1866:264-274. [PMID: 28844746 DOI: 10.1016/j.bbapap.2017.08.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 07/07/2017] [Accepted: 08/07/2017] [Indexed: 12/17/2022]
Abstract
Phosphoribosyltransferases (PRTs) bind 5'-phospho-α-d-ribosyl-1'-pyrophosphate (PRPP) and transfer its phosphoribosyl group (PRib) to specific nucleophiles. Anthranilate PRT (AnPRT) is a promiscuous PRT that can phosphoribosylate both anthranilate and alternative substrates, and is the only example of a type III PRT. Comparison of the PRPP binding mode in type I, II and III PRTs indicates that AnPRT does not bind PRPP, or nearby metals, in the same conformation as other PRTs. A structure with a stereoisomer of PRPP bound to AnPRT from Mycobacterium tuberculosis (Mtb) suggests a catalytic or post-catalytic state that links PRib movement to metal movement. Crystal structures of Mtb-AnPRT in complex with PRPP and with varying occupancies of the two metal binding sites, complemented by activity assay data, indicate that this type III PRT binds a single metal-coordinated species of PRPP, while an adjacent second metal site can be occupied due to a separate binding event. A series of compounds were synthesized that included a phosphonate group to probe PRPP binding site. Compounds containing a "bianthranilate"-like moiety are inhibitors with IC50 values of 10-60μM, and Ki values of 1.3-15μM. Structures of Mtb-AnPRT in complex with these compounds indicate that their phosphonate moieties are unable to mimic the binding modes of the PRib or pyrophosphate moieties of PRPP. The AnPRT structures presented herein indicated that PRPP binds a surface cleft and becomes enclosed due to re-positioning of two mobile loops.
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Affiliation(s)
- Genevieve L Evans
- Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Biological Sciences, University of Auckland, 3 Symonds Street, Auckland 1142, New Zealand.
| | - Daniel P Furkert
- Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Chemical Sciences, University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand
| | - Nacim Abermil
- Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Chemical Sciences, University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand
| | - Preeti Kundu
- Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; Biomolecular Interaction Centre, University of Canterbury, P. O. Box 4800, Christchurch 8140, New Zealand; Department of Chemistry, University of Canterbury, P. O. Box 4800, Christchurch 8140, New Zealand
| | - Katrina M de Lange
- Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Biological Sciences, University of Auckland, 3 Symonds Street, Auckland 1142, New Zealand
| | - Emily J Parker
- Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; Biomolecular Interaction Centre, University of Canterbury, P. O. Box 4800, Christchurch 8140, New Zealand; Department of Chemistry, University of Canterbury, P. O. Box 4800, Christchurch 8140, New Zealand
| | - Margaret A Brimble
- Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Chemical Sciences, University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand
| | - Edward N Baker
- Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Biological Sciences, University of Auckland, 3 Symonds Street, Auckland 1142, New Zealand
| | - J Shaun Lott
- Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Biological Sciences, University of Auckland, 3 Symonds Street, Auckland 1142, New Zealand.
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5
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Phosphoribosyl Diphosphate (PRPP): Biosynthesis, Enzymology, Utilization, and Metabolic Significance. Microbiol Mol Biol Rev 2016; 81:81/1/e00040-16. [PMID: 28031352 DOI: 10.1128/mmbr.00040-16] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Phosphoribosyl diphosphate (PRPP) is an important intermediate in cellular metabolism. PRPP is synthesized by PRPP synthase, as follows: ribose 5-phosphate + ATP → PRPP + AMP. PRPP is ubiquitously found in living organisms and is used in substitution reactions with the formation of glycosidic bonds. PRPP is utilized in the biosynthesis of purine and pyrimidine nucleotides, the amino acids histidine and tryptophan, the cofactors NAD and tetrahydromethanopterin, arabinosyl monophosphodecaprenol, and certain aminoglycoside antibiotics. The participation of PRPP in each of these metabolic pathways is reviewed. Central to the metabolism of PRPP is PRPP synthase, which has been studied from all kingdoms of life by classical mechanistic procedures. The results of these analyses are unified with recent progress in molecular enzymology and the elucidation of the three-dimensional structures of PRPP synthases from eubacteria, archaea, and humans. The structures and mechanisms of catalysis of the five diphosphoryltransferases are compared, as are those of selected enzymes of diphosphoryl transfer, phosphoryl transfer, and nucleotidyl transfer reactions. PRPP is used as a substrate by a large number phosphoribosyltransferases. The protein structures and reaction mechanisms of these phosphoribosyltransferases vary and demonstrate the versatility of PRPP as an intermediate in cellular physiology. PRPP synthases appear to have originated from a phosphoribosyltransferase during evolution, as demonstrated by phylogenetic analysis. PRPP, furthermore, is an effector molecule of purine and pyrimidine nucleotide biosynthesis, either by binding to PurR or PyrR regulatory proteins or as an allosteric activator of carbamoylphosphate synthetase. Genetic analyses have disclosed a number of mutants altered in the PRPP synthase-specifying genes in humans as well as bacterial species.
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Youn HS, Kim TG, Kim MK, Kang GB, Kang JY, Lee JG, An JY, Park KR, Lee Y, Im YJ, Lee JH, Eom SH. Structural Insights into the Quaternary Catalytic Mechanism of Hexameric Human Quinolinate Phosphoribosyltransferase, a Key Enzyme in de novo NAD Biosynthesis. Sci Rep 2016; 6:19681. [PMID: 26805589 PMCID: PMC4726147 DOI: 10.1038/srep19681] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 12/14/2015] [Indexed: 11/09/2022] Open
Abstract
Quinolinate phosphoribosyltransferase (QPRT) catalyses the production of nicotinic
acid mononucleotide, a precursor of de novo biosynthesis of the ubiquitous
coenzyme nicotinamide adenine dinucleotide. QPRT is also essential for maintaining
the homeostasis of quinolinic acid in the brain, a possible neurotoxin causing
various neurodegenerative diseases. Although QPRT has been extensively analysed, the
molecular basis of the reaction catalysed by human QPRT remains unclear. Here, we
present the crystal structures of hexameric human QPRT in the apo form and its
complexes with reactant or product. We found that the interaction between dimeric
subunits was dramatically altered during the reaction process by conformational
changes of two flexible loops in the active site at the dimer-dimer interface. In
addition, the N-terminal short helix α1 was identified as a critical
hexamer stabilizer. The structural features, size distribution, heat aggregation and
ITC studies of the full-length enzyme and the enzyme lacking helix α1
strongly suggest that human QPRT acts as a hexamer for cooperative reactant binding
via three dimeric subunits and maintaining stability. Based on our comparison of
human QPRT structures in the apo and complex forms, we propose a drug design
strategy targeting malignant glioma.
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Affiliation(s)
- Hyung-Seop Youn
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea.,Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
| | - Tae Gyun Kim
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea.,Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
| | - Mun-Kyoung Kim
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
| | - Gil Bu Kang
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
| | - Jung Youn Kang
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea.,Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
| | - Jung-Gyu Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea.,Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
| | - Jun Yop An
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea.,Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
| | - Kyoung Ryoung Park
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea.,Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
| | - Youngjin Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea.,Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
| | - Young Jun Im
- College of Pharmacy, Chonnam National University, Gwangju 500-757, South Korea
| | - Jun Hyuck Lee
- Division of Polar Life Sciences, Korea Polar Research Institute, Incheon 406-840, South Korea.,Department of Polar Sciences, Korea University of Science and Technology, Incheon 406-840, South Korea
| | - Soo Hyun Eom
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea.,Steitz Center for Structural Biology, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea.,Department of Chemistry, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
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7
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Kim H, Shibayama K, Rimbara E, Mori S. Biochemical characterization of quinolinic acid phosphoribosyltransferase from Mycobacterium tuberculosis H37Rv and inhibition of its activity by pyrazinamide. PLoS One 2014; 9:e100062. [PMID: 24949952 PMCID: PMC4065032 DOI: 10.1371/journal.pone.0100062] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 05/22/2014] [Indexed: 11/19/2022] Open
Abstract
Quinolinic acid phosphoribosyltransferase (QAPRTase, EC 2.4.2.19) is a key enzyme in the de novo pathway of nicotinamide adenine dinucleotide (NAD) biosynthesis and a target for the development of new anti-tuberculosis drugs. QAPRTase catalyzes the synthesis of nicotinic acid mononucleotide from quinolinic acid (QA) and 5-phosphoribosyl-1-pyrophosphate (PRPP) through a phosphoribosyl transfer reaction followed by decarboxylation. The crystal structure of QAPRTase from Mycobacterium tuberculosis H37Rv (MtQAPRTase) has been determined; however, a detailed functional analysis of MtQAPRTase has not been published. Here, we analyzed the enzymatic activities of MtQAPRTase and determined the effect on catalysis of the anti-tuberculosis drug pyrazinamide (PZA). The optimum temperature and pH for MtQAPRTase activity were 60°C and pH 9.2. MtQAPRTase required bivalent metal ions and its activity was highest in the presence of Mg2+. Kinetic analyses revealed that the Km values for QA and PRPP were 0.08 and 0.39 mM, respectively, and the kcat values for QA and PRPP were 0.12 and 0.14 [s-1], respectively. When the amino acid residues of MtQAPRTase, which may interact with QA, were substituted with alanine residues, catalytic activity was undetectable. Further, PZA, which is an anti-tuberculosis drug and a structural analog of QA, markedly inhibited the catalytic activity of MtQAPRTase. The structure of PZA may provide the basis for the design of new inhibitors of MtQAPRTase. These findings provide new insights into the catalytic properties of MtQAPRTase.
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Affiliation(s)
- Hyun Kim
- Department of Bacteriology II, National Institute of Infectious Diseases, Musashi-Murayama, Tokyo, Japan
| | - Keigo Shibayama
- Department of Bacteriology II, National Institute of Infectious Diseases, Musashi-Murayama, Tokyo, Japan
| | - Emiko Rimbara
- Department of Bacteriology II, National Institute of Infectious Diseases, Musashi-Murayama, Tokyo, Japan
| | - Shigetarou Mori
- Department of Bacteriology II, National Institute of Infectious Diseases, Musashi-Murayama, Tokyo, Japan
- * E-mail:
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8
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Malik SS, Patterson DN, Ncube Z, Toth EA. The crystal structure of human quinolinic acid phosphoribosyltransferase in complex with its inhibitor phthalic acid. Proteins 2013; 82:405-14. [PMID: 24038671 DOI: 10.1002/prot.24406] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 07/31/2013] [Accepted: 08/21/2013] [Indexed: 11/07/2022]
Abstract
Quinolinic acid (QA), a biologically potent but neurodestructive metabolite is catabolized by quinolinic acid phosphoribosyltransferase (QPRT) in the first step of the de novo NAD(+) biosynthesis pathway. This puts QPRT at the junction of two different pathways, that is, de novo NAD(+) biosynthesis and the kynurenine pathway of tryptophan degradation. Thus, QPRT is an important enzyme in terms of its biological impact and its potential as a therapeutic target. Here, we report the crystal structure of human QPRT bound to its inhibitor phthalic acid (PHT) and kinetic analysis of PHT inhibition of human QPRT. This structure, determined at 2.55 Å resolution, shows an elaborate hydrogen bonding network that helps in recognition of PHT and consequently its substrate QA. In addition to this hydrogen bonding network, we observe extensive van der Waals contacts with the PHT ring that might be important for correctly orientating the substrate QA during catalysis. Moreover, our crystal form allows us to observe an intact hexamer in both the apo- and PHT-bound forms in the same crystal system, which provides a direct comparison of unique subunit interfaces formed in hexameric human QPRT. We call these interfaces "nondimeric interfaces" to distinguish them from the typical dimeric interfaces observed in all QPRTs. We observe significant changes in the nondimeric interfaces in the QPRT hexamer upon binding PHT. Thus, the new structural and functional features of this enzyme we describe here will aid in understanding the function of hexameric QPRTs, which includes all eukaryotic and select prokaryotic QPRTs.
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Affiliation(s)
- Shuja S Malik
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201
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9
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Youn HS, Kim MK, Kang GB, Kim TG, Lee JG, An JY, Park KR, Lee Y, Kang JY, Song HE, Park I, Cho C, Fukuoka SI, Eom SH. Crystal structure of Sus scrofa quinolinate phosphoribosyltransferase in complex with nicotinate mononucleotide. PLoS One 2013; 8:e62027. [PMID: 23626766 PMCID: PMC3633916 DOI: 10.1371/journal.pone.0062027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 03/17/2013] [Indexed: 11/25/2022] Open
Abstract
We have determined the crystal structure of porcine quinolinate phosphoribosyltransferase (QAPRTase) in complex with nicotinate mononucleotide (NAMN), which is the first crystal structure of a mammalian QAPRTase with its reaction product. The structure was determined from protein obtained from the porcine kidney. Because the full protein sequence of porcine QAPRTase was not available in either protein or nucleotide databases, cDNA was synthesized using reverse transcriptase-polymerase chain reaction to determine the porcine QAPRTase amino acid sequence. The crystal structure revealed that porcine QAPRTases have a hexameric structure that is similar to other eukaryotic QAPRTases, such as the human and yeast enzymes. However, the interaction between NAMN and porcine QAPRTase was different from the interaction found in prokaryotic enzymes, such as those of Helicobacter pylori and Mycobacterium tuberculosis. The crystal structure of porcine QAPRTase in complex with NAMN provides a structural framework for understanding the unique properties of the mammalian QAPRTase active site and designing new antibiotics that are selective for the QAPRTases of pathogenic bacteria, such as H. pylori and M. tuberculosis.
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Affiliation(s)
- Hyung-Seop Youn
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
- Stetiz Center for Structural Biology, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Mun-Kyoung Kim
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Gil Bu Kang
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Tae Gyun Kim
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
- Stetiz Center for Structural Biology, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Jung-Gyu Lee
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
- Stetiz Center for Structural Biology, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Jun Yop An
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
- Stetiz Center for Structural Biology, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Kyoung Ryoung Park
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
- Stetiz Center for Structural Biology, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Youngjin Lee
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
- Stetiz Center for Structural Biology, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Jung Youn Kang
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
- Stetiz Center for Structural Biology, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Hye-Eun Song
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Inju Park
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Chunghee Cho
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
| | - Shin-Ichi Fukuoka
- School of Culture and Creative Studies, Aoyama Gakuin University, Tokyo, Japan
| | - Soo Hyun Eom
- School of Life Sciences, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
- Stetiz Center for Structural Biology, Gwangju Institute of Science & Technology, Gwangju, Republic of Korea
- * E-mail:
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10
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Youn HS, Kim MK, Kang GB, Kim TG, An JY, Lee JG, Park KR, Lee Y, Fukuoka SI, Eom SH. Crystallization and preliminary X-ray crystallographic analysis of quinolinate phosphoribosyltransferase from porcine kidney in complex with nicotinate mononucleotide. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012. [PMID: 23192029 DOI: 10.1107/s1744309112040638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Quinolinate phosphoribosyltransferase (QAPRTase) is a key enzyme in NAD biosynthesis; it catalyzes the formation of nicotinate mononucleotide (NAMN) from quinolinate and 5-phosphoribosyl-1-pyrophosphate. In order to elucidate the mechanism of NAMN biosynthesis, crystals of Sus scrofa QAPRTase (Ss-QAPRTase) purified from porcine kidney in complex with NAMN were obtained and diffraction data were collected and processed to 2.1 Å resolution. The Ss-QAPRTase-NAMN cocrystals belonged to space group P321, with unit-cell parameters a=119.1, b=119.1, c=93.7 Å, γ=120.0°. The Matthews coefficient and the solvent content were estimated as 3.10 Å3 Da(-1) and 60.3%, respectively, assuming the presence of two molecules in the asymmetric unit.
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Affiliation(s)
- Hyung-Seop Youn
- School of Life Sciences, Cell Dynamics Research Center, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
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11
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di Luccio E, Koehl P. A quality metric for homology modeling: the H-factor. BMC Bioinformatics 2011; 12:48. [PMID: 21291572 PMCID: PMC3213331 DOI: 10.1186/1471-2105-12-48] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Accepted: 02/04/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The analysis of protein structures provides fundamental insight into most biochemical functions and consequently into the cause and possible treatment of diseases. As the structures of most known proteins cannot be solved experimentally for technical or sometimes simply for time constraints, in silico protein structure prediction is expected to step in and generate a more complete picture of the protein structure universe. Molecular modeling of protein structures is a fast growing field and tremendous works have been done since the publication of the very first model. The growth of modeling techniques and more specifically of those that rely on the existing experimental knowledge of protein structures is intimately linked to the developments of high resolution, experimental techniques such as NMR, X-ray crystallography and electron microscopy. This strong connection between experimental and in silico methods is however not devoid of criticisms and concerns among modelers as well as among experimentalists. RESULTS In this paper, we focus on homology-modeling and more specifically, we review how it is perceived by the structural biology community and what can be done to impress on the experimentalists that it can be a valuable resource to them. We review the common practices and provide a set of guidelines for building better models. For that purpose, we introduce the H-factor, a new indicator for assessing the quality of homology models, mimicking the R-factor in X-ray crystallography. The methods for computing the H-factor is fully described and validated on a series of test cases. CONCLUSIONS We have developed a web service for computing the H-factor for models of a protein structure. This service is freely accessible at http://koehllab.genomecenter.ucdavis.edu/toolkit/h-factor.
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Affiliation(s)
- Eric di Luccio
- Computer Science Department, Room 4337, Genome Center, GBSF University of California Davis 451 East Health Sciences Drive Davis, CA 95616, USA.
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12
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Kang GB, Kim MK, Youn HS, An JY, Lee JG, Park KR, Lee SH, Kim Y, Fukuoka SI, Eom SH. Crystallization and preliminary X-ray crystallographic analysis of human quinolinate phosphoribosyltransferase. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 67:38-40. [PMID: 21206019 DOI: 10.1107/s1744309110041011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Accepted: 10/12/2010] [Indexed: 11/10/2022]
Abstract
Quinolinate phosphoribosyltransferase (QPRTase) is a key NAD-biosynthetic enzyme which catalyzes the transfer of quinolinic acid to 5-phosphoribosyl-1-pyrophosphate, yielding nicotinic acid mononucleotide. Homo sapiens QPRTase (Hs-QPRTase) appeared as a hexamer during purification and the protein was crystallized. Diffraction data were collected and processed at 2.8 Å resolution. Native Hs-QPRTase crystals belonged to space group P2(1), with unit-cell parameters a=76.2, b=137.1, c=92.7 Å, β=103.8°. Assuming the presence of six molecules in the asymmetric unit, the calculated Matthews coefficient is 2.46 Å3 Da(-1), which corresponds to a solvent content of 49.9%.
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Affiliation(s)
- Gil Bu Kang
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
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13
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Oades RD, Myint AM, Dauvermann MR, Schimmelmann BG, Schwarz MJ. Attention-deficit hyperactivity disorder (ADHD) and glial integrity: an exploration of associations of cytokines and kynurenine metabolites with symptoms and attention. Behav Brain Funct 2010; 6:32. [PMID: 20534153 PMCID: PMC2900218 DOI: 10.1186/1744-9081-6-32] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 06/09/2010] [Indexed: 12/24/2022] Open
Abstract
Background In contrast to studies of depression and psychosis, the first part of this study showed no major differences in serum levels of cytokines and tryptophan metabolites between healthy children and those with attention-deficit/hyperactivity disorder of the combined type (ADHD). Yet, small decreases of potentially toxic kynurenine metabolites and increases of cytokines were evident in subgroups. Therefore we examined predictions of biochemical associations with the major symptom clusters, measures of attention and response variability. Methods We explored systematically associations of 8 cytokines (indicators of pro/anti-inflammatory function) and 5 tryptophan metabolites with symptom ratings (e.g. anxiety, opposition, inattention) and continuous performance test (CPT) measures (e.g. movement, response time (RT), variability) in 35 ADHD (14 on medication) and 21 control children. Predictions from linear regressions (controlled by the false discovery rate) confirmed or disconfirmed partial correlations accounting for age, body mass and socio-economic status. Results (1) Total symptom ratings were associated with increases of the interleukins IL-16 and IL-13, where relations of IL-16 (along with decreased S100B) with hyperactivity, and IL-13 with inattention were notable. Opposition ratings were predicted by increased IL-2 in ADHD and IL-6 in control children. (2) In the CPT, IL-16 related to motor measures and errors of commission, while IL-13 was associated with errors of omission. Increased RT variability related to lower TNF-α, but to higher IFN-γ levels. (3) Tryptophan metabolites were not significantly related to symptoms. But increased tryptophan predicted errors of omission, its breakdown predicted errors of commission and kynurenine levels related to faster RTs. Conclusions Many associations were found across diagnostic groups even though they were more marked in one group. This confirms the quantitative trait nature of these features. Conceptually the relationships of the pro- and antiinflammatory cytokines distinguished between behaviours associated more with cognitive or more with motor control respectively. Further study should extend the number of immunological and metabolic markers to confirm or refute the trends reported here and examine their stability from childhood to adolescence in a longitudinal design.
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Affiliation(s)
- Robert D Oades
- Clinic for Child and Adolescent Psychiatry and Psychotherapy, University of Duisburg-Essen, 45147 Essen, Germany
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Oades RD, Dauvermann MR, Schimmelmann BG, Schwarz MJ, Myint AM. Attention-deficit hyperactivity disorder (ADHD) and glial integrity: S100B, cytokines and kynurenine metabolism--effects of medication. BEHAVIORAL AND BRAIN FUNCTIONS : BBF 2010; 6:29. [PMID: 20509936 PMCID: PMC2889842 DOI: 10.1186/1744-9081-6-29] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Accepted: 05/28/2010] [Indexed: 12/30/2022]
Abstract
BACKGROUND Children with attention-deficit/hyperactivity disorder (ADHD) show a marked temporal variability in their display of symptoms and neuropsychological performance. This could be explained in terms of an impaired glial supply of energy to support neuronal activity. METHOD We pursued one test of the idea with measures of a neurotrophin reflecting glial integrity (S100B) and the influences of 8 cytokines on the metabolism of amino-acids, and of tryptophan/kynurenine to neuroprotective or potentially toxic products that could modulate glial function. Serum samples from 21 medication-naïve children with ADHD, 21 typically-developing controls, 14 medicated children with ADHD and 7 healthy siblings were analysed in this preliminary exploration of group differences and associations. RESULTS There were no marked group differences in levels of S100B, no major imbalance in the ratios of pro- to anti-inflammatory interleukins nor in the metabolism of kynurenine to toxic metabolites in ADHD. However, four trends are described that may be worthy of closer examination in a more extensive study. First, S100B levels tended to be lower in ADHD children that did not show oppositional/conduct problems. Second, in medicated children raised interleukin levels showed a trend to normalisation. Third, while across all children the sensitivity to allergy reflected increased levels of IL-16 and IL-10, the latter showed a significant inverse relationship to measures of S100B in the ADHD group. Fourthly, against expectations healthy controls tended to show higher levels of toxic 3-hydroxykynurenine (3 HK) than those with ADHD. CONCLUSIONS Thus, there were no clear signs (S100B) that the glial functions were compromised in ADHD. However, other markers of glial function require examination. Nonetheless there is preliminary evidence that a minor imbalance of the immunological system was improved on medication. Finally, if lower levels of the potentially toxic 3 HK in ADHD children were confirmed this could reflect a reduction of normal pruning processes in the brain that would be consistent with delayed maturation (supported here by associations with amino-acid metabolism) and a reduced metabolic source of energy.
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Affiliation(s)
- Robert D Oades
- Clinic for Child and Adolescent Psychiatry and Psychotherapy, University of Duisburg-Essen, 45147 Essen Germany
| | - Maria R Dauvermann
- Clinic for Child and Adolescent Psychiatry and Psychotherapy, University of Duisburg-Essen, 45147 Essen Germany
| | - Benno G Schimmelmann
- Child and Adolescent Psychiatry, University of Bern, Effingerstr. 12, 3011 Bern, Switzerland
| | - Markus J Schwarz
- Laboratory for Psychoneuroimmunology, Ludwig Maximillian's University Psychiatric Hospital, 8036 Munich, Germany
| | - Aye-Mu Myint
- Laboratory for Psychoneuroimmunology, Ludwig Maximillian's University Psychiatric Hospital, 8036 Munich, Germany
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Bello Z, Stitt B, Grubmeyer C. Interactions at the 2 and 5 positions of 5-phosphoribosyl pyrophosphate are essential in Salmonella typhimurium quinolinate phosphoribosyltransferase. Biochemistry 2010; 49:1377-87. [PMID: 20047307 DOI: 10.1021/bi9018219] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Quinolinate phosphoribosyltransferase (QAPRTase, EC 2.4.2.19) catalyzes an unusual phosphoribosyl transfer that is linked to a decarboxylation reaction to form the NAD precursor nicotinate mononucleotide, carbon dioxide, and pyrophosphate from quinolinic acid (QA) and 5-phosphoribosyl 1-pyrophosphate (PRPP). Structural studies and sequence similarities with other PRTases have implicated Glu214, Asp235, Lys153, and Lys284 in contributing to catalysis through direct interaction with PRPP. The four residues were substituted by site-directed mutagenesis. A nadC deletant form of BL21DE3 was created to eliminate trace contamination by chromosomal QAPRTase. The mutant enzymes were readily purified and retained their dimeric aggregation state on gel filtration. Substitution of Lys153 with Ala resulted in an inactive enzyme, indicating its essential nature. Mutation of Glu214 to Ala or Asp caused at least a 4000-fold reduction in k(cat), with 10-fold increases in K(m) and K(D) values for PRPP. However, mutation of Glu214 to Gln had only modest effects on ligand binding and catalysis. pH profiles indicated that the deprotonated form of a residue with pK(a) of 6.9 is essential for catalysis. The WT-like pH profile of the E214Q mutant indicated that Glu214 is not that residue. Mutation of Asp235 to Ala did not affect ligand binding or catalysis. Mutation of Lys284 to Ala decreased k(cat) by 30-fold and increased K(m) and K(D) values for PRPP by 80-fold and at least 20-fold, respectively. The study suggests that Lys153 is necessary for catalysis and important for PRPP binding, Glu214 provides a hydrogen bond necessary for catalysis but does not act as a base or electrostatically to stabilize the transition state, Lys284 is involved in PRPP binding, and Asp235 is not essential.
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Affiliation(s)
- Zainab Bello
- Fels Institute for Cancer Research and Molecular Biology and Department of Biochemistry, Temple University School of Medicine, 3307 North Broad Street, Philadelphia, Pennsylvania 19140, USA
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Bello Z, Grubmeyer C. Roles for cationic residues at the quinolinic acid binding site of quinolinate phosphoribosyltransferase. Biochemistry 2010; 49:1388-95. [PMID: 20047306 DOI: 10.1021/bi9018225] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Quinolinic acid phosphoribosyltransferase (QAPRTase, EC 2.4.2.19) forms nicotinate mononucleotide (NAMN) from quinolinic acid (QA) and 5-phosphoribosyl 1-pyrophosphate (PRPP). Previously determined crystal structures of QAPRTase.QA and QAPRTase.PA.PRPP complexes show positively charged residues (Arg118, Arg152, Arg175, Lys185, and His188) lining the QA binding site. To assess the roles of these residues in the Salmonella typhimurium QAPRTase reaction, they were individually mutated to alanine and the recombinant proteins overexpressed and purified from a recombineered Escherichia coli strain that lacks the QAPRTase gene. Gel filtration indicated that the mutations did not affect the dimeric aggregation state of the enzymes. Arg175 is critical for the QAPRTase reaction, and its mutation to alanine produced an inactive enzyme. The k(cat) values for R152A and K185A were reduced by 33-fold and 625-fold, and binding affinity of PRPP and QA to the enzymes decreased. R152A and K185A mutants displayed 116-fold and 83-fold increases in activity toward the normally inactive QA analogue, nicotinic acid (NA), indicating roles for these residues in defining the substrate specificity of QAPRTase. Moreover, K185A QAPRTase displayed a 300-fold higher k(cat)/K(m) for NA over the natural substrate QA. Pre-steady-state analysis of K185A with QA revealed a burst of nucleotide formation followed by a slower steady-state rate, unlike the linear kinetics of WT. Intriguingly, pre-steady-state analysis of K185A with NA produced a rapid but linear rate for NAMN formation. The result implies a critical role for Lys185 in the chemistry of the QAPRTase intermediate. Arg118 is an essential residue that reaches across the dimer interface. Mutation of Arg118 to alanine resulted in 5000-fold decrease in k(cat) value and a decrease in the binding affinity of QA and PRPP to R152A. Equimolar mixtures of R118A with inactive or virtually inactive mutants produced approximately 50% of the enzymatic activity of WT, establishing an interfacial role for Arg118 during catalysis.
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Affiliation(s)
- Zainab Bello
- Fels Institute for Cancer Research and Molecular Biology and Department of Biochemistry, Temple University School of Medicine, 3307 North Broad Street, Philadelphia, Pennsylvania 19140, USA
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Current awareness on yeast. Yeast 2008. [DOI: 10.1002/yea.1558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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