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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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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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