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Shumar SA, Kerr EW, Geldenhuys WJ, Montgomery GE, Fagone P, Thirawatananond P, Saavedra H, Gabelli SB, Leonardi R. Nudt19 is a renal CoA diphosphohydrolase with biochemical and regulatory properties that are distinct from the hepatic Nudt7 isoform. J Biol Chem 2018; 293:4134-4148. [PMID: 29378847 PMCID: PMC5857999 DOI: 10.1074/jbc.ra117.001358] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 01/26/2018] [Indexed: 12/31/2022] Open
Abstract
CoA is the major acyl carrier in mammals and a key cofactor in energy metabolism. Dynamic regulation of CoA in different tissues and organs supports metabolic flexibility. Two mammalian Nudix hydrolases, Nudt19 and Nudt7, degrade CoA in vitro Nudt19 and Nudt7 possess conserved Nudix and CoA signature sequences and specifically hydrolyze the diphosphate bond of free CoA and acyl-CoAs to form 3',5'-ADP and 4'-(acyl)phosphopantetheine. Limited information is available on these enzymes, but the relatively high abundance of Nudt19 and Nudt7 mRNA in the kidney and liver, respectively, suggests that they play specific roles in the regulation of CoA levels in these organs. Here, we analyzed Nudt19-/- mice and found that deletion of Nudt19 elevates kidney CoA levels in mice fed ad libitum, indicating that Nudt19 contributes to the regulation of CoA in vivo Unlike what was observed for the regulation of Nudt7 in the liver, Nudt19 transcript and protein levels in the kidney did not differ between fed and fasted states. Instead, we identified chenodeoxycholic acid as a specific Nudt19 inhibitor that competed with CoA for Nudt19 binding but did not bind to Nudt7. Exchange of the Nudix and CoA signature motifs between the two isoforms dramatically decreased their kcat Furthermore, substitutions of conserved residues within these motifs identified amino acids playing different roles in CoA binding and hydrolysis in Nudt19 and Nudt7. Our results reveal that the kidney and liver each possesses a distinct peroxisomal CoA diphosphohydrolase.
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Affiliation(s)
| | | | - Werner J Geldenhuys
- Pharmaceutical Sciences, West Virginia University, Morgantown, West Virginia 26501 and
| | | | | | - Puchong Thirawatananond
- the Departments of Biophysics and Biophysical Chemistry
- Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | | | - Sandra B Gabelli
- the Departments of Biophysics and Biophysical Chemistry
- Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Medicine, and
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2
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Muthuramalingam M, Zeng X, Iyer NJ, Klein P, Mahalingam R. A GCC-box motif in the promoter of nudix hydrolase 7 (AtNUDT7) gene plays a role in ozone response of Arabidopsis ecotypes. Genomics 2015; 105:31-8. [PMID: 25451743 DOI: 10.1016/j.ygeno.2014.10.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 10/15/2014] [Accepted: 10/29/2014] [Indexed: 01/01/2023]
Abstract
Arabidopsis nudix hydrolase 7 (AtNudt7) plays an important role in regulating redox homeostasis during stress/defense signaling and seed germination. The early responsiveness of AtNudt7 provides a useful marker especially during oxidative cell death in plants. Nuclear run-on assays demonstrate that AtNudt7 is transcriptionally regulated. AtNUDT7 promoter-GUS transgenic plants show rapid inducibility in response to ozone and pathogens. A 16-bp insertion containing a GCC-box motif was identified in the promoter of a Ws-2 ecotype and was absent in Col-0. The 16-bp sequence was identified in 5% of the Arabidopsis ecotypes used in the 1001 genome sequencing project. The kinetics of expression of Ethylene Response Factor 1 (ERF1), a GCC-box binding factor is in synchrony with expression of AtNudt7 in response to ozone stress. ERF1 protein binds to the GCC-box motif in the AtNUDT7 promoter. In silico analysis of erf1 mutant and overexpressor lines supports a role for this protein in regulating AtNUDT7 expression.
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Affiliation(s)
| | - Xin Zeng
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA
| | - Niranjani J Iyer
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA
| | - Peter Klein
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Ramamurthy Mahalingam
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
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3
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Barta ML, Lovell S, Sinclair AN, Battaile KP, Hefty PS. Chlamydia trachomatis CT771 (nudH) is an asymmetric Ap4A hydrolase. Biochemistry 2014; 53:214-24. [PMID: 24354275 DOI: 10.1021/bi401473e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Asymmetric diadenosine 5',5‴-P(1),P(4)-tetraphosphate (Ap4A) hydrolases are members of the Nudix superfamily that asymmetrically cleave the metabolite Ap4A into ATP and AMP while facilitating homeostasis. The obligate intracellular mammalian pathogen Chlamydia trachomatis possesses a single Nudix family protein, CT771. As pathogens that rely on a host for replication and dissemination typically have one or zero Nudix family proteins, this suggests that CT771 could be critical for chlamydial biology and pathogenesis. We identified orthologues to CT771 within environmental Chlamydiales that share active site residues suggesting a common function. Crystal structures of both apo- and ligand-bound CT771 were determined to 2.6 Å and 1.9 Å resolution, respectively. The structure of CT771 shows a αβα-sandwich motif with many conserved elements lining the putative Nudix active site. Numerous aspects of the ligand-bound CT771 structure mirror those observed in the ligand-bound structure of the Ap4A hydrolase from Caenorhabditis elegans. These structures represent only the second Ap4A hydrolase enzyme member determined from eubacteria and suggest that mammalian and bacterial Ap4A hydrolases might be more similar than previously thought. The aforementioned structural similarities, in tandem with molecular docking, guided the enzymatic characterization of CT771. Together, these studies provide the molecular details for substrate binding and specificity, supporting the analysis that CT771 is an Ap4A hydrolase (nudH).
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Affiliation(s)
- Michael L Barta
- Department of Molecular Biosciences, University of Kansas , Lawrence, Kansas 66045, United States
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Jiang YL, Zhang JW, Yu WL, Cheng W, Zhang CC, Frolet C, Di Guilmi AM, Vernet T, Zhou CZ, Chen Y. Structural and enzymatic characterization of the streptococcal ATP/diadenosine polyphosphate and phosphodiester hydrolase Spr1479/SapH. J Biol Chem 2011; 286:35906-35914. [PMID: 21865160 PMCID: PMC3195627 DOI: 10.1074/jbc.m111.228585] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2011] [Revised: 08/04/2011] [Indexed: 01/07/2023] Open
Abstract
Spr1479 from Streptococcus pneumoniae R6 is a 33-kDa hypothetical protein of unknown function. Here, we determined the crystal structures of its apo-form at 1.90 Å and complex forms with inorganic phosphate and AMP at 2.30 and 2.20 Å, respectively. The core structure of Spr1479 adopts a four-layer αββα-sandwich fold, with Fe(3+) and Mn(2+) coordinated at the binuclear center of the active site (similar to metallophosphoesterases). Enzymatic assays showed that, in addition to phosphodiesterase activity for bis(p-nitrophenyl) phosphate, Spr1479 has hydrolase activity for diadenosine polyphosphate (Ap(n)A) and ATP. Residues that coordinate with the two metals are indispensable for both activities. By contrast, the streptococcus-specific residue Trp-67, which binds to phosphate in the two complex structures, is indispensable for the ATP/Ap(n)A hydrolase activity only. Moreover, the AMP-binding pocket is conserved exclusively in all streptococci. Therefore, we named the protein SapH for streptococcal ATP/Ap(n)A and phosphodiester hydrolase.
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Affiliation(s)
- Yong-Liang Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jun-Wei Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wei-Li Yu
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wang Cheng
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Chen-Chen Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Cecile Frolet
- Laboratoire d'Ingénierie des Macromolécules, Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075, 41 rue Jules Horowitz, 38027 Grenoble, France
| | - Anne-Marie Di Guilmi
- Laboratoire d'Ingénierie des Macromolécules, Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075, 41 rue Jules Horowitz, 38027 Grenoble, France
| | - Thierry Vernet
- Laboratoire d'Ingénierie des Macromolécules, Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075, 41 rue Jules Horowitz, 38027 Grenoble, France
| | - Cong-Zhao Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Yuxing Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
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Sharma A, Tendulkar AV, Wangikar PP. Structure based prediction of functional sites with potential inhibitors to Nudix enzymes from disease causing microbes. Bioinformation 2011; 5:341-9. [PMID: 21383922 PMCID: PMC3046039 DOI: 10.6026/97320630005341] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 12/30/2010] [Indexed: 11/23/2022] Open
Abstract
The functional sites were predicted for Nudix enzymes from pathogenic microorganisms such as Streprococcus pneumonia (2B06) and Enterococcus
faecalis (2AZW). Their structures are already determined, however, no data is reported about their functional sites, substrates and inhibitors. Therefore,
we report prediction of functional sites in these Nudix enzymes via Geometric Invariant (GI) technique (Construct different geometries of peptides which
remain unchanged). The GI method enumerated 2B06: RA57, EA58, EA61, EA62 and 2AZW: RA62, EA63, EA66, EA67 as putative functional sites in
these Nudix enzymes. In addition, the substrate was predicted via Molecular docking (Docking of substrates against whole structure of Nudix enzymes).
The substrate ADP-Ribose was docked with the Nudix enzymes, 2B06 (Docking energy -15.68 Kcal/mol) and 2AZW (Docking energy -10.86 Kcal/mol)
with the higher affinity and the lower docking energy as compared to other substrates. The residues EA62 in 2B06 and RA62 in 2AZW make hydrogen
bonds with the ADP-ribose. Furthermore, we screened 51 inhibitor compounds against structures of 2B06 and 2AZW. The inhibitor compounds AMPCPR
and CID14258187 were docked well as compared to other compounds. The compound CID14258187 was also in agreement with Lipinski rule of 5 for
drug likeness properties. Therefore, our findings of functional sites, substrates and inhibitors for these Nudix enzymes may help in structure based drug
designing against Streprococcus pneumonia and Enterococcus faecalis
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Affiliation(s)
- Ashwani Sharma
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai- 400 076, Maharashtra, India
| | - Ashish Vijay Tendulkar
- Department of Computer Science and Engineering, Indian Institute of Technology Madras, Chennai- 600036, Indi
| | - Pramod Prabhakar Wangikar
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai- 400076, Maharashtra, Indi
- Pramod P. Wangikar:
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Dong H, Qin S, Zhou HX. Effects of macromolecular crowding on protein conformational changes. PLoS Comput Biol 2010; 6:e1000833. [PMID: 20617196 PMCID: PMC2895631 DOI: 10.1371/journal.pcbi.1000833] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2009] [Accepted: 05/25/2010] [Indexed: 01/29/2023] Open
Abstract
Many protein functions can be directly linked to conformational changes. Inside cells, the equilibria and transition rates between different conformations may be affected by macromolecular crowding. We have recently developed a new approach for modeling crowding effects, which enables an atomistic representation of “test” proteins. Here this approach is applied to study how crowding affects the equilibria and transition rates between open and closed conformations of seven proteins: yeast protein disulfide isomerase (yPDI), adenylate kinase (AdK), orotidine phosphate decarboxylase (ODCase), Trp repressor (TrpR), hemoglobin, DNA β-glucosyltransferase, and Ap4A hydrolase. For each protein, molecular dynamics simulations of the open and closed states are separately run. Representative open and closed conformations are then used to calculate the crowding-induced changes in chemical potential for the two states. The difference in chemical-potential change between the two states finally predicts the effects of crowding on the population ratio of the two states. Crowding is found to reduce the open population to various extents. In the presence of crowders with a 15 Å radius and occupying 35% of volume, the open-to-closed population ratios of yPDI, AdK, ODCase and TrpR are reduced by 79%, 78%, 62% and 55%, respectively. The reductions for the remaining three proteins are 20–44%. As expected, the four proteins experiencing the stronger crowding effects are those with larger conformational changes between open and closed states (e.g., as measured by the change in radius of gyration). Larger proteins also tend to experience stronger crowding effects than smaller ones [e.g., comparing yPDI (480 residues) and TrpR (98 residues)]. The potentials of mean force along the open-closed reaction coordinate of apo and ligand-bound ODCase are altered by crowding, suggesting that transition rates are also affected. These quantitative results and qualitative trends will serve as valuable guides for expected crowding effects on protein conformation changes inside cells. The biophysical properties of proteins inside cells can be expected to be quite different from those typically measured by in vitro experiments in dilute solutions. In particular, intracellular macromolecular crowding may significantly affect the equilibria and transition rates between different conformations of a protein, and hence its functions. What are the trends and magnitudes of such crowding effects? We address this question here by applying a recently developed approach for modeling crowding. Seven proteins, each with structures for both an open state and a closed state, are studied. Crowding exerts significant effects on the open-closed equilibria of four proteins and more modest effects on the remaining three. Potentials of mean force along the open-closed reaction coordinate, and hence transition rates, are similarly affected. The extent of conformational changes is the main determinant for the magnitudes of crowding effects, but the protein size also plays an important role. The effects of crowding become stronger as the protein size increases. Conformational transitions of the ribosome, an extremely large complex, during translation are predicted to experience particularly strong effects of intracellular crowding. We conclude that deduction of intracellular behaviors from in vitro experiments requires explicit consideration of crowding effects.
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Affiliation(s)
- Hao Dong
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America
| | - Sanbo Qin
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America
| | - Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, United States of America
- * E-mail:
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7
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Jeyakanthan J, Kanaujia SP, Nishida Y, Nakagawa N, Praveen S, Shinkai A, Kuramitsu S, Yokoyama S, Sekar K. Free and ATP-bound structures of Ap4A hydrolase from Aquifex aeolicus V5. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2010; 66:116-24. [PMID: 20124691 DOI: 10.1107/s0907444909047064] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Accepted: 11/07/2009] [Indexed: 11/10/2022]
Abstract
Asymmetric diadenosine tetraphosphate (Ap(4)A) hydrolases degrade the metabolite Ap(4)A back into ATP and AMP. The three-dimensional crystal structure of Ap(4)A hydrolase (16 kDa) from Aquifex aeolicus has been determined in free and ATP-bound forms at 1.8 and 1.95 A resolution, respectively. The overall three-dimensional crystal structure of the enzyme shows an alphabetaalpha-sandwich architecture with a characteristic loop adjacent to the catalytic site of the protein molecule. The ATP molecule is bound in the primary active site and the adenine moiety of the nucleotide binds in a ring-stacking arrangement equivalent to that observed in the X-ray structure of Ap(4)A hydrolase from Caenorhabditis elegans. Binding of ATP in the active site induces local conformational changes which may have important implications in the mechanism of substrate recognition in this class of enzymes. Furthermore, two invariant water molecules have been identified and their possible structural and/or functional roles are discussed. In addition, modelling of the substrate molecule at the primary active site of the enzyme suggests a possible path for entry and/or exit of the substrate and/or product molecule.
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Affiliation(s)
- Jeyaraman Jeyakanthan
- Life Science Group, National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan
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8
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Liu YC, Yang MH, Lin WL, Huang CK, Oyang YJ. A sequence-based hybrid predictor for identifying conformationally ambivalent regions in proteins. BMC Genomics 2009; 10 Suppl 3:S22. [PMID: 19958486 PMCID: PMC2788375 DOI: 10.1186/1471-2164-10-s3-s22] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Background Proteins are dynamic macromolecules which may undergo conformational transitions upon changes in environment. As it has been observed in laboratories that protein flexibility is correlated to essential biological functions, scientists have been designing various types of predictors for identifying structurally flexible regions in proteins. In this respect, there are two major categories of predictors. One category of predictors attempts to identify conformationally flexible regions through analysis of protein tertiary structures. Another category of predictors works completely based on analysis of the polypeptide sequences. As the availability of protein tertiary structures is generally limited, the design of predictors that work completely based on sequence information is crucial for advances of molecular biology research. Results In this article, we propose a novel approach to design a sequence-based predictor for identifying conformationally ambivalent regions in proteins. The novelty in the design stems from incorporating two classifiers based on two distinctive supervised learning algorithms that provide complementary prediction powers. Experimental results show that the overall performance delivered by the hybrid predictor proposed in this article is superior to the performance delivered by the existing predictors. Furthermore, the case study presented in this article demonstrates that the proposed hybrid predictor is capable of providing the biologists with valuable clues about the functional sites in a protein chain. The proposed hybrid predictor provides the users with two optional modes, namely, the high-sensitivity mode and the high-specificity mode. The experimental results with an independent testing data set show that the proposed hybrid predictor is capable of delivering sensitivity of 0.710 and specificity of 0.608 under the high-sensitivity mode, while delivering sensitivity of 0.451 and specificity of 0.787 under the high-specificity mode. Conclusion Though experimental results show that the hybrid approach designed to exploit the complementary prediction powers of distinctive supervised learning algorithms works more effectively than conventional approaches, there exists a large room for further improvement with respect to the achieved performance. In this respect, it is of interest to investigate the effects of exploiting additional physiochemical properties that are related to conformational ambivalence. Furthermore, it is of interest to investigate the effects of incorporating lately-developed machine learning approaches, e.g. the random forest design and the multi-stage design. As conformational transition plays a key role in carrying out several essential types of biological functions, the design of more advanced predictors for identifying conformationally ambivalent regions in proteins deserves our continuous attention.
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Affiliation(s)
- Yu-Cheng Liu
- Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, Republic of China.
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Branson KM, Mertens HDT, Swarbrick JD, Fletcher JI, Kedzierski L, Gayler KR, Gooley PR, Smith BJ. Discovery of inhibitors of lupin diadenosine 5',5'''-P(1),P(4)-tetraphosphate hydrolase by virtual screening. Biochemistry 2009; 48:7614-20. [PMID: 19603790 DOI: 10.1021/bi900813x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Novel inhibitors of lupin diadenosine 5',5'''-P(1),P(4)-tetraphosphate (Ap(4)A) hydrolase have been identified by in silico screening of a large virtual chemical library. Compounds were ranked on the basis of a consensus from six scoring functions. From the top 100 ranked compounds six were selected and initially screened for inhibitory activity using a single concentration isothermal titration calorimetry assay. Two of these compounds that showed excellent solubility properties were further analyzed, but only one [NSC51531; 2-((8-hydroxy-4-(4-methyl-2-sulfoanilino)-9,10-dioxo-9,10-dihydro-1-anthracenyl)amino)-5-methylbenzenesulfonic acid] exhibited competitive inhibition with a K(i) of 1 microM. A structural analogue of this compound also exhibited competitive inhibition with a comparable K(i) of 2.9 microM. (1)H, (15)N NMR spectroscopy was used to map the binding site of NSC51531 on lupin Ap(4)A hydrolase and demonstrated that the compound bound specifically in the substrate-binding site, consistent with the competitive inhibition results. Binding of NSC51531 to the human form of Ap(4)A hydrolase is nonspecific, suggesting that this compound may represent a useful lead in the design of specific inhibitors of the plant-like form of Ap(4)A hydrolases.
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Affiliation(s)
- Kim M Branson
- Structural Biology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
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10
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Garza JA, Ilangovan U, Hinck AP, Barnes LD. Kinetic, dynamic, ligand binding properties, and structural models of a dual-substrate specific nudix hydrolase from Schizosaccharomyces pombe. Biochemistry 2009; 48:6224-39. [PMID: 19462967 DOI: 10.1021/bi802266g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Schizosaccharomyces pombe Aps1 is a nudix hydrolase that catalyzes the hydrolysis of both diadenosine 5',5'''-P(1),P(n)-oligophosphates and diphosphoinositol polyphosphates in vitro. Nudix hydrolases act upon a wide variety of substrates, despite having a common 23 amino acid catalytic motif; hence, the residues responsible for substrate specificity are considered to reside outside the common catalytic nudix motif. The specific residues involved in binding each substrate of S. pombe Aps1 are unknown. In this study, we have conducted mutational and kinetic studies in combination with structural homology modeling and NMR spectroscopic analyses to identify potential residues involved in binding each class of substrates. This study demonstrates several major findings with regard to Aps1. First, the determination of the kinetic parameters of K(m) and k(cat) indicated that the initial 31 residues of Aps1 are not involved in substrate binding or catalysis with respect to Ap(6)A. Second, NMR spectroscopic analyses revealed the secondary structure and three dynamic backbone regions, one of which corresponds to a large insert in Aps1 as compared to other putative fungal orthologues. Third, two structural models of Aps1Delta2-19, based on the crystal structures of human DIPP1 and T. thermophilus Ndx1, were generated using homology modeling. The structural models were in excellent agreement with the NMR-derived secondary structure of Aps1Delta2-19. Fourth, NMR chemical shift mapping in conjunction with structural homology models indicated several residues outside the catalytic nudix motif that are involved in specific binding of diphosphoinositol polyphosphate or diadenosine oligophosphate ligands.
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Affiliation(s)
- John A Garza
- Department of Biochemistry, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, USA
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Gunawardana D, Likic VA, Gayler KR. A comprehensive bioinformatics analysis of the Nudix superfamily in Arabidopsis thaliana. Comp Funct Genomics 2009; 2009:820381. [PMID: 19590748 PMCID: PMC2707057 DOI: 10.1155/2009/820381] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2008] [Accepted: 04/16/2009] [Indexed: 11/17/2022] Open
Abstract
Nudix enzymes are a superfamily with a conserved common reaction mechanism that provides the capacity for the hydrolysis of a broad spectrum of metabolites. We used hidden Markov models based on Nudix sequences from the PFAM and PROSITE databases to identify Nudix hydrolases encoded by the Arabidopsis genome. 25 Nudix hydrolases were identified and classified into 11 individual families by pairwise sequence alignments. Intron phases were strikingly conserved in each family. Phylogenetic analysis showed that all multimember families formed monophyletic clusters. Conserved familial sequence motifs were identified with the MEME motif analysis algorithm. One motif (motif 4) was found in three diverse families. All proteins containing motif 4 demonstrated a degree of preference for substrates containing an ADP moiety. We conclude that HMM model-based genome scanning and MEME motif analysis, respectively, can significantly improve the identification and assignment of function of new members of this mechanistically-diverse protein superfamily.
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Affiliation(s)
- D. Gunawardana
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
- School of Biological Sciences, University of Sydney, New South Wales 2006, Australia
| | - V. A. Likic
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - K. R. Gayler
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
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12
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Structure and biological function of the RNA pyrophosphohydrolase BdRppH from Bdellovibrio bacteriovorus. Structure 2009; 17:472-81. [PMID: 19278661 DOI: 10.1016/j.str.2008.12.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 12/08/2008] [Accepted: 12/29/2008] [Indexed: 11/22/2022]
Abstract
Until recently, the mechanism of mRNA decay in bacteria was thought to be different from that of eukaryotes. This paradigm changed with the discovery that RppH (ORF176/NudH/YgdP), an Escherichia coli enzyme that belongs to the Nudix superfamily, is an RNA pyrophosphohydrolase that initiates mRNA decay by cleaving pyrophosphate from the 5'-triphosphate. Here we report the 1.9 Angstroms resolution structure of the Nudix hydrolase BdRppH from Bdellovibrio bacteriovorus, a bacterium that feeds on other Gram-negative bacteria. Based on the structure of the enzyme alone and in complex with GTP-Mg2+, we propose a mode of RNA binding similar to that of the nuclear decapping enzyme from Xenopus laevis, X29. In additional experiments, we show that BdRppH can indeed function in vitro and in vivo as an RNA pyrophosphohydrolase. These findings set the basis for the identification of possible decapping enzymes in other bacteria.
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13
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Gunawardana D, Cheng HC, Gayler KR. Identification of functional domains in Arabidopsis thaliana mRNA decapping enzyme (AtDcp2). Nucleic Acids Res 2007; 36:203-16. [PMID: 18025047 PMCID: PMC2248764 DOI: 10.1093/nar/gkm1002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The Arabidopsis thaliana decapping enzyme (AtDcp2) was characterized by bioinformatics analysis and by biochemical studies of the enzyme and mutants produced by recombinant expression. Three functionally significant regions were detected: (i) a highly disordered C-terminal region with a putative PSD-95, Discs-large, ZO-1 (PDZ) domain-binding motif, (ii) a conserved Nudix box constituting the putative active site and (iii) a putative RNA binding domain consisting of the conserved Box B and a preceding loop region. Mutation of the putative PDZ domain-binding motif improved the stability of recombinant AtDcp2 and secondary mutants expressed in Escherichia coli. Such recombinant AtDcp2 specifically hydrolysed capped mRNA to produce 7-methyl GDP and decapped RNA. AtDcp2 activity was Mn(2+)- or Mg(2+)-dependent and was inhibited by the product 7-methyl GDP. Mutation of the conserved glutamate-154 and glutamate-158 in the Nudix box reduced AtDcp2 activity up to 400-fold and showed that AtDcp2 employs the catalytic mechanism conserved amongst Nudix hydrolases. Unlike many Nudix hydrolases, AtDcp2 is refractory to inhibition by fluoride ions. Decapping was dependent on binding to the mRNA moiety rather than to the 7-methyl diguanosine triphosphate cap of the substrate. Mutational analysis of the putative RNA-binding domain confirmed the functional significance of an 11-residue loop region and the conserved Box B.
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Affiliation(s)
- Dilantha Gunawardana
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
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14
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Zha M, Zhong C, Peng Y, Hu H, Ding J. Crystal structures of human NUDT5 reveal insights into the structural basis of the substrate specificity. J Mol Biol 2006; 364:1021-33. [PMID: 17052728 DOI: 10.1016/j.jmb.2006.09.078] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2006] [Revised: 09/27/2006] [Accepted: 09/27/2006] [Indexed: 11/23/2022]
Abstract
Human NUDT5 (hNUDT5) is an ADP-ribose pyrophosphatase (ADPRase) belonging to the Nudix hydrolase superfamily. It presumably plays important roles in controlling the intracellular level of ADP-ribose (ADPR) to prevent non-enzymatic ADP-ribosylation by hydrolyzing ADPR to AMP and ribose 5'-phosphate. We report here the crystal structures of hNUDT5 in apo form, in complex with ADPR, and in complex with AMP with bound Mg2+. hNUDT5 forms a homodimer with substantial domain swapping and assumes a structure more similar to Escherichia coli ADPRase ORF209 than human ADPRase NUDT9. The adenine moiety of the substrates is specifically recognized by the enzyme via hydrogen-bonding interactions between N1 and N6 of the base and Glu47 of one subunit, and between N7 of the base and Arg51 of the other subunit, providing the molecular basis for the high selectivity of hNUDT5 for ADP-sugars over other sugar nucleotides. Structural comparisons with E. coli ADPRase ORF209 and ADPXase ORF186 indicate that the existence of an aromatic residue on loop L8 in ORF186 seems to be positively correlated with its enzymatic activity on APnA, whereas hNUDT5 and ORF209 contain no such residue and thus have low or no activities on APnA.
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Affiliation(s)
- Manwu Zha
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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15
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Guranowski A, Starzyńska E, Pietrowska-Borek M, Jemielity J, Kowalska J, Darzynkiewicz E, Thompson MJ, Blackburn GM. Methylene analogues of adenosine 5'-tetraphosphate. Their chemical synthesis and recognition by human and plant mononucleoside tetraphosphatases and dinucleoside tetraphosphatases. FEBS J 2006; 273:829-38. [PMID: 16441668 DOI: 10.1111/j.1742-4658.2006.05115.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Adenosine 5'-polyphosphates have been identified in vitro, as products of certain enzymatic reactions, and in vivo. Although the biological role of these compounds is not known, there exist highly specific hydrolases that degrade nucleoside 5'-polyphosphates into the corresponding nucleoside 5'-triphosphates. One approach to understanding the mechanism and function of these enzymes is through the use of specifically designed phosphonate analogues. We synthesized novel nucleotides: alpha,beta-methylene-adenosine 5'-tetraphosphate (pppCH2pA), beta,gamma-methylene-adenosine 5'-tetraphosphate (ppCH2ppA), gamma,delta-methylene-adenosine 5'-tetraphosphate (pCH2pppA), alphabeta,gammadelta-bismethylene-adenosine 5'-tetraphosphate (pCH2ppCH2pA), alphabeta, betagamma-bismethylene-adenosine 5'-tetraphosphate (ppCH2pCH2pA) and betagamma, gammadelta-bis(dichloro)methylene-adenosine 5'-tetraphosphate (pCCl2pCCl2ppA), and tested them as potential substrates and/or inhibitors of three specific nucleoside tetraphosphatases. In addition, we employed these p4A analogues with two asymmetrically and one symmetrically acting dinucleoside tetraphosphatases. Of the six analogues, only pppCH2pA is a substrate of the two nucleoside tetraphosphatases (EC 3.6.1.14), from yellow lupin seeds and human placenta, and also of the yeast exopolyphosphatase (EC 3.6.1.11). Surprisingly, none of the six analogues inhibited these p4A-hydrolysing enzymes. By contrast, the analogues strongly inhibit the (asymmetrical) dinucleoside tetraphosphatases (EC 3.6.1.17) from human and the narrow-leafed lupin. ppCH2ppA and pCH2pppA, inhibited the human enzyme with Ki values of 1.6 and 2.3 nm, respectively, and the lupin enzyme with Ki values of 30 and 34 nm, respectively. They are thereby identified as being the strongest inhibitors ever reported for the (asymmetrical) dinucleoside tetraphosphatases. The three analogues having two halo/methylene bridges are much less potent inhibitors for these enzymes. These novel nucleotides should prove valuable tools for further studies on the cellular functions of mono- and dinucleoside polyphosphates and on the enzymes involved in their metabolism.
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Affiliation(s)
- Andrzej Guranowski
- Department of Biochemistry and Biotechnology, Agricultural University, Poznań, Poland.
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16
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Zheng QC, Li ZS, Sun M, Zhang Y, Sun CC. Homology modeling and substrate binding study of Nudix hydrolase Ndx1 from Thermos thermophilus HB8. Biochem Biophys Res Commun 2005; 333:881-7. [PMID: 15963459 DOI: 10.1016/j.bbrc.2005.05.169] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Accepted: 05/24/2005] [Indexed: 10/25/2022]
Abstract
With homology modeling techniques, molecular mechanics, and molecular dynamics methods, a 3D structure model of Ndx1 is created and refined. This model is further assessed by Profile-3D and ProStat, which confirm that the refined model is reliable. With this model, a flexible docking study is performed and the result indicates that Glu46, Arg88, and Glu90 are three important determinant residues in binding, as they have strong hydrogen bonding interactions and electrostatic interactions with Ap6A. In addition, we further find that three residues, Ser38, Leu39 and Glu46, coordinate enzyme-bound Mg2+ ions in complex N-A. The Glu46 is consistent with the experimental results by Iwai et al., and the other four residues mentioned above may also play vital roles in catalysis of Ndx1.
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Affiliation(s)
- Qing-Chuan Zheng
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, PR China
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17
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Klaus SMJ, Wegkamp A, Sybesma W, Hugenholtz J, Gregory JF, Hanson AD. A nudix enzyme removes pyrophosphate from dihydroneopterin triphosphate in the folate synthesis pathway of bacteria and plants. J Biol Chem 2005; 280:5274-80. [PMID: 15611104 DOI: 10.1074/jbc.m413759200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Removal of pyrophosphate from dihydroneopterin triphosphate (DHNTP) is the second step in the pterin branch of the folate synthesis pathway. There has been controversy over whether this reaction requires a specific pyrophosphohydrolase or is a metal ion-dependent chemical process. The genome of Lactococcus lactis has a multicistronic folate synthesis operon that includes an open reading frame (ylgG) specifying a putative Nudix hydrolase. Because many Nudix enzymes are pyrophosphohydrolases, YlgG was expressed in Escherichia coli and characterized. The recombinant protein showed high DHNTP pyrophosphohydrolase activity with a K(m) value of 2 microM, had no detectable activity against deoxynucleoside triphosphates or other typical Nudix hydrolase substrates, required a physiological level (approximately 1 mM) of Mg(2+), and was active as a monomer. Essentially no reaction occurred without enzyme at 1 mM Mg(2+). Inactivation of ylgG in L. lactis resulted in DHNTP accumulation and folate depletion, confirming that YlgG functions in folate biosynthesis. We therefore propose that ylgG be redesignated as folQ. The closest Arabidopsis homolog of YlgG (encoded by Nudix gene At1g68760) was expressed in E. coli and shown to have Mg(2+)-dependent DHNTP pyrophosphohydrolase activity. This protein (AtNUDT1) was reported previously to have NADH pyrophosphatase activity in the presence of 5 mM Mn(2+) (Dobrzanska, M., Szurmak, B., Wyslouch-Cieszynska, A., and Kraszewska, E. (2002) J. Biol. Chem. 277, 50482-50486). However, we found that this activity is negligible at physiological levels of Mn(2+) and that, with 1 mM Mg(2+), AtNUDT1 prefers DHNTP and (deoxy) nucleoside triphosphates.
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Affiliation(s)
- Sebastian M J Klaus
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA
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18
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Swarbrick JD, Buyya S, Gunawardana D, Fletcher JI, Branson K, Smith B, Pepe S, McLennan AG, Gayler KR, Gooley PR. 1H, 13C, and 15N resonance assignments of the 17 kDa Ap4A hydrolase from Homo sapiens in the presence and absence of ATP. JOURNAL OF BIOMOLECULAR NMR 2005; 31:181-182. [PMID: 15772762 DOI: 10.1007/s10858-004-7440-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2004] [Accepted: 11/29/2004] [Indexed: 05/24/2023]
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19
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Mildvan AS, Xia Z, Azurmendi HF, Saraswat V, Legler PM, Massiah MA, Gabelli SB, Bianchet MA, Kang LW, Amzel LM. Structures and mechanisms of Nudix hydrolases. Arch Biochem Biophys 2005; 433:129-43. [PMID: 15581572 DOI: 10.1016/j.abb.2004.08.017] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2004] [Revised: 08/16/2004] [Indexed: 12/12/2022]
Abstract
Nudix hydrolases catalyze the hydrolysis of nucleoside diphosphates linked to other moieties, X, and contain the sequence motif or Nudix box, GX(5)EX(7)REUXEEXGU. The mechanisms of Nudix hydrolases are highly diverse in the position on the substrate at which nucleophilic substitution occurs, and in the number of required divalent cations. While most proceed by associative nucleophilic substitutions by water at specific internal phosphorus atoms of a diphosphate or polyphosphate chain, members of the GDP-mannose hydrolase sub-family catalyze dissociative nucleophilic substitutions, by water, at carbon. The site of substitution is likely determined by the positions of the general base and the entering water. The rate accelerations or catalytic powers of Nudix hydrolases range from 10(9)- to 10(12)-fold. The reactions are accelerated 10(3)-10(5)-fold by general base catalysis by a glutamate residue within, or beyond the Nudix box, or by a histidine beyond the Nudix box. Lewis acid catalysis, which contributes 10(3)-10(5)-fold to the rate acceleration, is provided by one, two, or three divalent cations. One divalent cation is coordinated by two or three conserved residues of the Nudix box, the initial glycine and one or two glutamate residues, together with a remote glutamate or glutamine ligand from beyond the Nudix box. Some Nudix enzymes require one (MutT) or two additional divalent cations (Ap(4)AP), to neutralize the charge of the polyphosphate chain, to help orient the attacking hydroxide or oxide nucleophile, and/or to facilitate the departure of the anionic leaving group. Additional catalysis (10-10(3)-fold) is provided by the cationic side chains of lysine and arginine residues and by H-bond donation by tyrosine residues, to orient the general base, or to promote the departure of the leaving group. The overall rate accelerations can be explained by both independent and cooperative effects of these catalytic components.
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Affiliation(s)
- A S Mildvan
- Department of Biological Chemistry, The Johns Hopkins School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205-2185, USA.
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20
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Swarbrick JD, Buyya S, Gunawardana D, Gayler KR, McLennan AG, Gooley PR. Structure and substrate-binding mechanism of human Ap4A hydrolase. J Biol Chem 2004; 280:8471-81. [PMID: 15596429 DOI: 10.1074/jbc.m412318200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Asymmetric diadenosine 5',5'''-P(1),P(4)-tetraphosphate (Ap(4)A) hydrolases play a major role in maintaining homeostasis by cleaving the metabolite diadenosine tetraphosphate (Ap(4)A) back into ATP and AMP. The NMR solution structures of the 17-kDa human asymmetric Ap(4)A hydrolase have been solved in both the presence and absence of the product ATP. The adenine moiety of the nucleotide predominantly binds in a ring stacking arrangement equivalent to that observed in the x-ray structure of the homologue from Caenorhabditis elegans. The binding site is, however, markedly divergent to that observed in the plant/pathogenic bacteria class of enzymes, opening avenues for the exploration of specific therapeutics. Binding of ATP induces substantial conformational and dynamic changes that were not observed in the C. elegans structure. In contrast to the C. elegans homologue, important side chains that play a major role in substrate binding do not have to reorient to accommodate the ligand. This may have important implications in the mechanism of substrate recognition in this class of enzymes.
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Affiliation(s)
- James D Swarbrick
- Department of Biochemistry and Molecular Biology, the University of Melbourne, Parkville, Victoria 3010, Australia
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21
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Gabelli SB, Bianchet MA, Azurmendi HF, Xia Z, Sarawat V, Mildvan AS, Amzel LM. Structure and mechanism of GDP-mannose glycosyl hydrolase, a Nudix enzyme that cleaves at carbon instead of phosphorus. Structure 2004; 12:927-35. [PMID: 15274914 DOI: 10.1016/j.str.2004.03.028] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2004] [Revised: 03/11/2004] [Accepted: 03/12/2004] [Indexed: 11/18/2022]
Abstract
GDP-mannose glycosyl hydrolase (GDPMH) catalyzes the hydrolysis of GDP-mannose and GDP-glucose to GDP and sugar by substitution with inversion at C1 of the sugar. The enzyme has a modified Nudix motif and requires one divalent cation for activity. The 1.3 A X-ray structure of the GDPMH-Mg(2+)-GDP complex, together with kinetic, mutational, and NMR data, suggests a mechanism for the GDPMH reaction. Several residues and the divalent cation strongly promote the departure of the GDP leaving group, supporting a dissociative mechanism. Comparison of the GDPMH structure with that of a typical Nudix hydrolase suggests how sequence changes result in the switch of catalytic activity from P-O bond cleavage to C-O bond cleavage. Changes in the Nudix motif result in loss of binding of at least one Mg(2+) ion, and shortening of a loop by 6 residues shifts the catalytic base by approximately 10 A.
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Affiliation(s)
- Sandra B Gabelli
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
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22
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Iwai T, Kuramitsu S, Masui R. The Nudix hydrolase Ndx1 from Thermus thermophilus HB8 is a diadenosine hexaphosphate hydrolase with a novel activity. J Biol Chem 2004; 279:21732-9. [PMID: 15024014 DOI: 10.1074/jbc.m312018200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ndx1 gene, which encodes a Nudix protein, was cloned from the extremely thermophilic bacterium Thermus thermophilus HB8. This gene encodes a 126-amino acid protein that includes the characteristic Nudix motif conserved among Nudix proteins. Ndx1 was overexpressed in Escherichia coli and purified. Ndx1 was stable up to 95 degrees C and at extreme pH. Size exclusion chromatography indicated that Ndx1 was monomeric in solution. Ndx1 specifically hydrolyzed (di)adenosine polyphosphates but not ATP or diadenosine triphosphate, and it always generated ATP as the product. Diadenosine hexaphosphate (Ap(6)A), the most preferred substrate, was hydrolyzed to produce two ATP molecules, which is a novel hydrolysis mode for Ap(6)A, with a K(m) of 1.4 microm and a k(cat) of 4.1 s(-1). These results indicate that Ndx1 is a (di)adenosine polyphosphate hydrolase. Ndx1 activity required the presence of the divalent cations Mn(2+), Mg(2+), Zn(2+), and Co(2+), whereas Ca(2+), Ni(2+), and Cu(2+) were not able to activate Ndx1. Fluoride ion inhibited Ndx1 activity via a non-competitive mechanism. Optimal activity for Ap(6)A was observed at around pH 8.0 and about 70 degrees C. We found two important residues with pK(a) values of 6.1 and 9.6 in the free enzyme and pK(a) values of 7.9 and 10.0 in the substrate-enzyme complex. Kinetic studies of proteins with amino acid substitutions suggested that Glu-46 and Glu-50 were conserved residues in the Nudix motif and were involved in catalysis. Trp-26 was likely involved in enzyme-substrate interactions based on fluorescence measurements. Based on these results, the mechanism of substrate recognition and catalysis are discussed.
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Affiliation(s)
- Takayoshi Iwai
- Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043
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23
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Ranatunga W, Hill EE, Mooster JL, Holbrook EL, Schulze-Gahmen U, Xu W, Bessman MJ, Brenner SE, Holbrook SR. Structural studies of the Nudix hydrolase DR1025 from Deinococcus radiodurans and its ligand complexes. J Mol Biol 2004; 339:103-16. [PMID: 15123424 DOI: 10.1016/j.jmb.2004.01.065] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2004] [Accepted: 01/29/2004] [Indexed: 11/20/2022]
Abstract
We have determined the crystal structure, at 1.4A, of the Nudix hydrolase DR1025 from the extremely radiation resistant bacterium Deinococcus radiodurans. The protein forms an intertwined homodimer by exchanging N-terminal segments between chains. We have identified additional conserved elements of the Nudix fold, including the metal-binding motif, a kinked beta-strand characterized by a proline two positions upstream of the Nudix consensus sequence, and participation of the N-terminal extension in the formation of the substrate-binding pocket. Crystal structures were also solved of DR1025 crystallized in the presence of magnesium and either a GTP analog or Ap(4)A (both at 1.6A resolution). In the Ap(4)A co-crystal, the electron density indicated that the product of asymmetric hydrolysis, ATP, was bound to the enzyme. The GTP analog bound structure showed that GTP was bound almost identically as ATP. Neither nucleoside triphosphate was further cleaved.
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Affiliation(s)
- Wasantha Ranatunga
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
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24
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Qu Y, Guo JT, Olman V, Xu Y. Protein structure prediction using sparse dipolar coupling data. Nucleic Acids Res 2004; 32:551-61. [PMID: 14744980 PMCID: PMC373331 DOI: 10.1093/nar/gkh204] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2003] [Revised: 12/10/2003] [Accepted: 12/10/2003] [Indexed: 12/17/2022] Open
Abstract
Residual dipolar coupling (RDC) represents one of the most exciting emerging NMR techniques for protein structure studies. However, solving a protein structure using RDC data alone is still a highly challenging problem. We report here a computer program, RDC-PROSPECT, for protein structure prediction based on a structural homolog or analog of the target protein in the Protein Data Bank (PDB), which best aligns with the (15)N-(1)H RDC data of the protein recorded in a single ordering medium. Since RDC-PROSPECT uses only RDC data and predicted secondary structure information, its performance is virtually independent of sequence similarity between a target protein and its structural homolog/analog, making it applicable to protein targets beyond the scope of current protein threading techniques. We have tested RDC-PROSPECT on all (15)N-(1)H RDC data (representing 43 proteins) deposited in the BioMagResBank (BMRB) database. The program correctly identified structural folds for 83.7% of the target proteins, and achieved an average alignment accuracy of 98.1% residues within a four-residue shift.
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Affiliation(s)
- Youxing Qu
- Computational Systems Biology Laboratory, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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25
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Shen BW, Perraud AL, Scharenberg A, Stoddard BL. The crystal structure and mutational analysis of human NUDT9. J Mol Biol 2003; 332:385-98. [PMID: 12948489 DOI: 10.1016/s0022-2836(03)00954-9] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Human ADP-ribose pyrophosphatase NUDT9 belongs to a superfamily of Nudix hydrolases that catabolize potentially toxic compounds in the cell. The enzyme hydrolyzes ADP-ribose (ADPR) to AMP and ribose 5'-phosphate. NUDT9 shares 39% sequence identity with the C-terminal cytoplasmic domain of the ADPR-gated calcium channel TRPM2, which exhibits low but specific enzyme activity. We determined crystal structures of NUDT9 in the presence and in the absence of the reaction product ribose 5'-phosphate. On the basis of these structures and comparison with a bacterial homologue, a model of the substrate complex was built. The structure and activity of a double point mutant (R(229)E(230)F(231) to R(229)I(230)L(231)), which mimics the Nudix signature of the ion channel domain, was determined. Finally, the activities of a pair of additional mutated constructs were compared to the wild-type enzyme. The first corresponds to a minimal Nudix domain missing an N-terminal domain and C-terminal tail; the second disrupts two potential general bases in the active site. NUDT9 contains an N-terminal domain with a novel fold and a catalytic C-terminal Nudix domain. Unlike its closest functional homologue (homodimeric Escherichia coli ADPRase), it is active as a monomer, and the substrate is bound in a cleft between the domains. The structure of the RIL mutant provides structural basis for the reduced activity of the TRPM2 ion channel. The conformation and binding interactions of ADPR substrate are predicted to differ from those observed for E.coli ADPRase; mutation of structurally aligned acidic residues in their active sites produce significantly different effects on catalytic efficiency, indicating that their reaction pathways and mechanisms may have diverged.
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Affiliation(s)
- Betty W Shen
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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26
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Guranowski A, Starzyńska E, McLennan AG, Baraniak J, Stec WJ. Adenosine-5'-O-phosphorylated and adenosine-5'-O-phosphorothioylated polyols as strong inhibitors of (symmetrical) and (asymmetrical) dinucleoside tetraphosphatases. Biochem J 2003; 373:635-40. [PMID: 12697025 PMCID: PMC1223503 DOI: 10.1042/bj20030320] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2003] [Revised: 04/15/2003] [Accepted: 04/16/2003] [Indexed: 01/25/2023]
Abstract
Dinucleoside 5',5"'- P (1), P ( n )-polyphosphates, and particularly the diadenosine compounds, have been implicated in extracellular purinergic signalling and in various intracellular processes, including DNA metabolism, tumour suppression and stress responses. If permitted to accumulate, they may also be toxic. One approach to understanding their function is through the various specific degradative enzymes that regulate their levels. Eight adenosine-5'- O -phosphorylated polyols (derivatives of glycerol, erythritol and pentaerythritol) and 11 adenosine-5'- O -phosphorothioylated polyols (derivatives of glycerol, erythritol, pentaerythritol, butanediol and pentanediol) have been tested as inhibitors of specific diadenosine tetraphosphate (Ap(4)A) hydrolases. Of these two groups of novel nucleotides, the adenosine-5'- O -phosphorothioylated polyols were generally stronger inhibitors than their adenosine-5'- O -phosphorylated counterparts. 1,4-Di(adenosine-5'- O -phosphorothio) erythritol appeared to be the strongest inhibitor of ( asymmetrical ) Ap(4)A hydrolases (EC 3.6.1.17) from both lupin and human, with K (i) values of 0.15 microM and 1.5 microM respectively. Of eight adenosine-5'- O -phosphorylated polyols, 1,4-di(adenosine-5'- O -phospho) erythritol was the only compound that inhibited the lupin enzyme. Two derivatives of pentaerythritol, di(adenosine-5'- O -phosphorothio)-di(phosphorothio) pentaerythritol and tri(adenosine-5'- O -phosphorothio)-phosphorothio-pentaerythritol, proved to be the strongest inhibitors of the prokaryotic ( symmetrical ) Ap(4)A hydrolase (EC 3.6.1.41) so far reported. The estimated K (i) values were 0.04 microM and 0.08 microM respectively. All of these inhibitors were competitive with respect to Ap(4)A. These new selectively acting Ap(4)A analogues should prove to be valuable tools for further studies of Ap(4)A function and of the enzymes involved in its metabolism.
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Affiliation(s)
- Andrzej Guranowski
- Department of Biochemistry and Biotechnology, University of Agriculture, 60-637 Poznań, Poland.
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27
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Kang LW, Gabelli SB, Bianchet MA, Xu WL, Bessman MJ, Amzel LM. Structure of a coenzyme A pyrophosphatase from Deinococcus radiodurans: a member of the Nudix family. J Bacteriol 2003; 185:4110-8. [PMID: 12837785 PMCID: PMC164880 DOI: 10.1128/jb.185.14.4110-4118.2003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gene Dr1184 from Deinococcus radiodurans codes for a Nudix enzyme (DR-CoAse) that hydrolyzes the pyrophosphate moiety of coenzyme A (CoA). Nudix enzymes with the same specificity have been found in yeast, humans, and mice. The three-dimensional structure of DR-CoAse, the first of a Nudix hydrolase with this specificity, reveals that this enzyme contains, in addition to the fold observed in other Nudix enzymes, insertions that are characteristic of a CoA-hydrolyzing Nudix subfamily. The structure of the complex of the enzyme with Mg(2+), its activating cation, reveals the position of the catalytic site. A helix, part of the N-terminal insertion, partially occludes the binding site and has to change its position to permit substrate binding. Comparison of the structure of DR-CoAse to those of other Nudix enzymes, together with the location in the structure of the sequence characteristic of CoAses, suggests a mode of binding of the substrate to the enzyme that is compatible with all available data.
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Affiliation(s)
- Lin-Woo Kang
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Pitcher WH, Kirby TW, DeRose EF, London RE. Metabolic transformation of AZTp4A by Ap4A hydrolase regenerates AZT triphosphate. Antiviral Res 2003; 58:227-33. [PMID: 12767470 DOI: 10.1016/s0166-3542(03)00003-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The reverse transcriptase (RT) of HIV which has been inhibited by the incorporation of AZT into the primer strand is subject to a deblocking reaction by cellular ATP. This reaction yields unblocked primer plus the dinucleoside tetraphosphate, AZTp(4)A. In the present study, we report that AZTp(4)A is an excellent substrate for the enzyme Ap(4)A hydrolase (asymmetrical dinucleoside tetraphosphatase, EC 3.6.1.17), an enzyme that is widely distributed in many cell types. Progress of the reaction has been monitored by 31P NMR, and it was found that hydrolysis results in the production of AZTTP:ATP in a 7:1 ratio. The AZTp(4)A was also hydrolyzed at a rate 1.8-fold more rapidly than Ap(4)A. Spectrophotometric assays yielded Michaelis constants of 2.35 and 0.71 microM for Ap(4)A and AZTp(4)A, respectively. It, therefore, appears that Ap(4)A hydrolase can play a useful role in the regeneration of the AZTTP, the active form of AZT, for the inhibition of HIV RT.
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Affiliation(s)
- Wayne H Pitcher
- Department of Health and Human Services, Laboratory of Structural Biology, MR-01, National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, NC 27709, USA
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29
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Abdelghany HM, Bailey S, Blackburn GM, Rafferty JB, McLennan AG. Analysis of the catalytic and binding residues of the diadenosine tetraphosphate pyrophosphohydrolase from Caenorhabditis elegans by site-directed mutagenesis. J Biol Chem 2003; 278:4435-9. [PMID: 12475970 DOI: 10.1074/jbc.m211983200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The contributions to substrate binding and catalysis of 13 amino acid residues of the Caenorhabditis elegans diadenosine tetraphosphate pyrophosphohydrolase (Ap(4)A hydrolase) predicted from the crystal structure of an enzyme-inhibitor complex have been investigated by site-directed mutagenesis. Sixteen glutathione S-transferase-Ap(4)A hydrolase fusion proteins were expressed and their k(cat) and K(m) values determined after removal of the glutathione S-transferase domain. As expected for a Nudix hydrolase, the wild type k(cat) of 23 s(-1) was reduced by 10(5)-, 10(3)-, and 30-fold, respectively, by replacement of the conserved P(4)-phosphate-binding catalytic residues Glu(56), Glu(52), and Glu(103) by Gln. K(m) values were not affected, indicating a lack of importance for substrate binding. In contrast, mutating His(31) to Val or Ala and Lys(83) to Met produced 10- and 16-fold increases in K(m) compared with the wild type value of 8.8 microm. These residues stabilize the P(1)-phosphate. H31V and H31A had a normal k(cat) but K83M showed a 37-fold reduction in k(cat). Lys(36) also stabilizes the P(1)-phosphate and a K36M mutant had a 10-fold reduced k(cat) but a relatively normal K(m). Thus both Lys(36) and Lys(83) may play a role in catalysis. The previously suggested roles of Tyr(27), His(38), Lys(79), and Lys(81) in stabilizing the P(2) and P(3)-phosphates were not confirmed by mutagenesis, indicating the absence of phosphate-specific binding contacts in this region. Also, mutating both Tyr(76) and Tyr(121), which clamp one substrate adenosine moiety between them in the crystal structure, to Ala only increased K(m) 4-fold. It is concluded that interactions with the P(1)- and P(4)-phosphates are minimum and sufficient requirements for substrate binding by this class of enzyme, indicating that it may have a much wider substrate range then previously believed.
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Affiliation(s)
- Hend M Abdelghany
- School of Biological Sciences, Biosciences Building, University of Liverpool, P. O. Box 147, Liverpool L69 7ZB, United Kingdom
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30
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Legler PM, Massiah MA, Mildvan AS. Mutational, kinetic, and NMR studies of the mechanism of E. coli GDP-mannose mannosyl hydrolase, an unusual Nudix enzyme. Biochemistry 2002; 41:10834-48. [PMID: 12196023 DOI: 10.1021/bi020362e] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
GDP-mannose mannosyl hydrolase (GDPMH) is an unusual Nudix family member, which catalyzes the hydrolysis of GDP-alpha-D-mannose to GDP and the beta-sugar by nucleophilic substitution at carbon rather than at phosphorus (Legler, P. M., Massiah, M. A., Bessman, M. J., and Mildvan, A. S. (2000) Biochemistry 39, 8603-8608). Using the structure and mechanism of MutT, the prototypical Nudix enzyme as a guide, we detected six catalytic residues of GDPMH, three of which were unique to GDPMH, by the kinetic and structural effects of site-specific mutations. Glu-70 (corresponding to Glu-57 in MutT) provides a ligand to the essential divalent cation on the basis of the effects of the E70Q mutation which decreased kcat 10(2.2)-fold, increased the dissociation constant of Mn2+ from the ternary E-Mn2+-GDP complex 3-fold, increased the K(m)Mg2+ 20-fold, and decreased the paramagnetic effect of Mn2+ on 1/T1 of water protons, indicating a change in the coordination sphere of Mn2+. In the E70Q mutant, Gln-70 was shown to be very near the active site metal ion by large paramagnetic effects of Mn2+ on its side chain -NH2 group. With wild-type GDPMH, the effect of pH on log(kcat/K(m)GDPmann) at 37 degrees C showed an ascending limb of unit slope, followed by a plateau yielding a pK(a) of 6.4, which increased to 6.7 +/- 0.1 in the pH dependence of log(kcat). The general base catalyst was identified as a neutral His residue by the DeltaH(ionization) = 7.0 +/- 0.7 kcal/mol, by the increase in pK(a) with ionic strength, and by mutation of each of the four histidine residues of GDPMH to Gln. Only the H124Q mutant showed the loss of the ascending limb in the pH versus log(kcat) rate profile, which was replaced by a weak dependence of rate on hydroxide concentration, as well as an overall 10(3.4)-fold decrease in kcat, indicating His-124 to be the general base, unlike MutT, which uses Glu-53 in this role. The H88Q mutant showed a 10(2.3)-fold decrease in kcat, a 4.4-fold increase in K(m)GDPmann, and no change in the pH versus log(kcat) rate profile, indicating an important but unidentified role of His-88 in catalysis. One and two-dimensional NMR studies permitted the sequence specific assignments of the imidazole HdeltaC, H(epsilon)C, N(delta), and N(epsilon) resonances of the four histidines and defined their protonation states. The pK(a) of His-124 (6.94 +/- 0.04) in the presence of saturating Mg2+ was comparable to the kinetically determined pK(a) at the same temperature (6.40 +/- 0.20). The other three histidines were neutral N(epsilon)H tautomers with pK(a) values below 5.5. Arg-52 and Arg-65 were identified as catalytic residues which interact electrostatically with the GDP leaving group by mutating these residues to Gln and Lys. The R52Q mutant decreased kcat 309-fold and increased K(m)GDPmann 40.6-fold, while the R52K mutant decreased kcat by only 12-fold and increased K(m)GDPmann 81-fold. The partial rescue of kcat, but not of K(m)GDPmann in the R52K mutant, suggests that Arg-52 is a bifunctional hydrogen bond donor to the GDP leaving group in the ground state and a monofunctional hydrogen bond donor in the transition state. Opposite behavior was found with the Arg-65 mutants, suggesting this residue to be a monofunctional hydrogen bond donor to the GDP leaving group in the ground state and a bifunctional hydrogen bond donor in the transition state. From these observations, a mechanism for GDPMH is proposed involving general base catalysis and electrostatic stabilization of the leaving group.
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Affiliation(s)
- Patricia M Legler
- Department of Biological Chemistry, The Johns Hopkins School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205-2185, USA
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31
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Gabelli SB, Bianchet MA, Ohnishi Y, Ichikawa Y, Bessman MJ, Amzel LM. Mechanism of the Escherichia coli ADP-ribose pyrophosphatase, a Nudix hydrolase. Biochemistry 2002; 41:9279-85. [PMID: 12135348 DOI: 10.1021/bi0259296] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Escherichia coli ADP-ribose (ADPR) pyrophosphatase (ADPRase), a Nudix enzyme, catalyzes the Mg(2+)-dependent hydrolysis of ADP-ribose to AMP and ribose 5-phosphate. ADPR hydrolysis experiments conducted in the presence of H(2)(18)O and analyzed by electrospray mass spectrometry showed that the ADPRase-catalyzed reaction takes place through nucleophilic attack at the adenosyl phosphate. The structure of ADPRase in complex with Mg(2+) and a nonhydrolyzable ADPR analogue, alpha,beta-methylene ADP-ribose, reveals an active site water molecule poised for nucleophilic attack on the adenosyl phosphate. This water molecule is activated by two magnesium ions, and its oxygen contacts the target phosphorus (P-O distance of 3.0 A) and forms an angle of 177 degrees with the scissile bond, suggesting an associative mechanism. A third Mg(2+) ion bridges the two phosphates and could stabilize the negative charge of the leaving group, ribose 5-phosphate. The structure of the ternary complex also shows that loop L9 moves fully 10 A from its position in the free enzyme, forming a tighter turn and bringing Glu 162 to its catalytic position. These observations indicate that as part of the catalytic mechanism, the ADPRase cycles between an open (free enzyme) and a closed (substrate-metal complex) conformation. This cycling may be important in preventing nonspecific hydrolysis of other nucleotides.
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Affiliation(s)
- Sandra B Gabelli
- Department of Biophysics and Biophysical Chemistry, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
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32
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Xu W, Gauss P, Shen J, Dunn CA, Bessman MJ. The gene e.1 (nudE.1) of T4 bacteriophage designates a new member of the Nudix hydrolase superfamily active on flavin adenine dinucleotide, adenosine 5'-triphospho-5'-adenosine, and ADP-ribose. J Biol Chem 2002; 277:23181-5. [PMID: 11976345 DOI: 10.1074/jbc.m203325200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The T4 bacteriophage gene e.1 was cloned into an expression vector and expressed in Escherichia coli, and the purified protein was identified as a Nudix hydrolase active on FAD, adenosine 5'-triphospho-5'-adenosine (Ap(3)A), and ADP-ribose. Typical of members of the Nudix hydrolases, the enzyme has an alkaline pH optimum (pH 8) and requires a divalent cation for activity that can be satisfied by Mg(2+) or Mn(2+). For all substrates, AMP is one of the products, and unlike most of the other enzymes active on Ap(3)A, the T4 enzyme hydrolyzes higher homologues including Ap(4-6)A. This is the first member of the Nudix hydrolase gene superfamily identified in bacterial viruses and the only one present in T4. Although the protein was predicted to be orthologous to E. coli MutT on the basis of a sequence homology search, the properties of the gene and of the purified protein do not support this notion because of the following. (a) The purified enzyme hydrolyzes substrates not acted upon by MutT, and it does not hydrolyze canonical MutT substrates. (b) The e.1 gene does not complement mutT1 in vivo. (c) The deletion of e.1 does not increase the spontaneous mutation frequency of T4 phage. The properties of the enzyme most closely resemble those of Orf186 of E. coli, the product of the nudE gene, and we therefore propose the mnemonic nudE.1 for the T4 phage orthologue.
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Affiliation(s)
- WenLian Xu
- Department of Biology and The McCollum-Pratt Institute, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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33
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Legler PM, Lee HC, Peisach J, Mildvan AS. Kinetic and magnetic resonance studies of the role of metal ions in the mechanism of Escherichia coli GDP-mannose mannosyl hydrolase, an unusual nudix enzyme. Biochemistry 2002; 41:4655-68. [PMID: 11926828 DOI: 10.1021/bi012118d] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Escherichia coli GDP-mannose mannosyl hydrolase (GDPMH), a homodimer, catalyzes the hydrolysis of GDP-alpha-D-sugars to yield the beta-D-sugar and GDP by nucleophilic substitution with inversion at the C1' carbon of the sugar [Legler, P. M., Massiah, M. A., Bessman, M. J., and Mildvan, A. S. (2000) Biochemistry 39, 8603-8608]. GDPMH requires a divalent cation for activity such as Mn2+ or Mg2+, which yield similar kcat values of 0.15 and 0.13 s(-1), respectively, at 22 degrees C and pH 7.5. Kinetic analysis of the Mn2+-activated enzyme yielded a K(m) of free Mn2+ of 3.9 +/- 1.3 mM when extrapolated to zero substrate concentration (K(a)Mn2+), which tightened to 0.32 +/- 0.18 mM when extrapolated to infinite substrate concentration (K(m)Mn2+). Similarly, the K(m) of the substrate extrapolated to zero Mn2+ concentration (K(S)(GDPmann) = 1.9 +/- 0.5 mM) and to infinite Mn2+ concentration (K(m)(GDPmann) = 0.16 +/- 0.09 mM) showed an order of magnitude decrease at saturating Mn2+. Such mutual tightening of metal and substrate binding suggests the formation of an enzyme-metal-substrate bridge complex. Direct Mn2+ binding studies, monitoring the concentration of free Mn2+ by EPR and of bound Mn2+ by its enhanced paramagnetic effect on the longitudinal relaxation rate of water protons (PRR), detected three Mn2+ binding sites per enzyme monomer with an average dissociation constant (K(D)) of 3.2 +/- 1.0 mM, in agreement with the kinetically determined K(a)Mn2+. The enhancement factor (epsilon(b)) of 11.5 +/- 1.2 indicates solvent access to the enzyme-bound Mn2+ ions. No cross relaxation was detected among the three bound Mn2+ ions, suggesting them to be separated by at least 10 A. Such studies also yielded a weak dissociation constant for the binary Mn2+-GDP-mannose complex (K1 = 6.5 +/- 1.0 mM) which significantly exceeded the kinetically determined K(m) values of Mn2+, indicating the true substrate to be GDP-mannose rather than its Mn2+ complex. Substrate binding monitored by changes in 1H-15N HSQC spectra yielded a dissociation constant for the binary E-GDP-mannose complex (K(S)(GDPmann)) of 4.0 +/- 0.5 mM, comparable to the kinetically determined K(S) value (1.9 +/- 0.5 mM). To clarify the metal stoichiometry at the active site, product inhibition by GDP, a potent competitive inhibitor (K(I) = 46 +/- 27 microM), was studied. Binding studies revealed a weak, binary E-GDP complex (K(D)(GDP) = 9.4 +/- 3.2 mM) which tightened approximately 500-fold in the presence of Mn2+ to yield a ternary E-Mn2+-GDP complex with a dissociation constant, K3(GDP) = 18 +/- 9 microM, which overlaps with the K(I)(GDP). The tight binding of Mn2+ to 0.7 +/- 0.2 site per enzyme subunit in the ternary E-Mn2+-GDP complex (K(A)' = 15 microM) and the tight binding of GDP to 0.8 +/- 0.1 site per enzyme subunit in the ternary E-Mg2+-GDP complex (K3 < 0.5 mM) indicate a stoichiometry close to 1:1:1 at the active site. The decrease in the enhancement factor of the ternary E-Mn2+-GDP complex (epsilon(T) = 4.9 +/- 0.4) indicates decreased solvent access to the active site Mn2+, consistent with an E-Mn2+-GDP bridge complex. Fermi contact splitting (4.3 +/- 0.2 MHz) of the phosphorus signal in the ESEEM spectrum established the formation of an inner sphere E-Mn2+-GDP complex. The number of water molecules coordinated to Mn2+ in this ternary complex was determined by ESEEM studies in D2O to be two fewer than on the average Mn2+ in the binary E-Mn2+ complexes, consistent with bidentate coordination of enzyme-bound Mn2+ by GDP. Kinetic, metal binding, and GDP binding studies with Mg2+ yielded dissociation constants similar to those found with Mn2+. Hence, GDPMH requires one divalent cation per active site to promote catalysis by facilitating the departure of the GDP leaving group, unlike its homologues the MutT pyrophosphohydrolase, which requires two, or Ap4A pyrophosphatase, which requires three.
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Affiliation(s)
- Patricia M Legler
- Department of Biological Chemistry, The Johns Hopkins School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205-2185, USA
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Bailey S, Sedelnikova SE, Blackburn GM, Abdelghany HM, Baker PJ, McLennan AG, Rafferty JB. The crystal structure of diadenosine tetraphosphate hydrolase from Caenorhabditis elegans in free and binary complex forms. Structure 2002; 10:589-600. [PMID: 11937063 DOI: 10.1016/s0969-2126(02)00746-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The crystal structure of C. elegans Ap(4)A hydrolase has been determined for the free enzyme and a binary complex at 2.0 A and 1.8 A, respectively. Ap(4)A hydrolase has a key role in regulating the intracellular Ap(4)A levels and hence potentially the cellular response to metabolic stress and/or differentiation and apoptosis via the Ap(3)A/Ap(4)A ratio. The structures reveal that the enzyme has the mixed alpha/beta fold of the Nudix family and also show how the enzyme binds and locates its substrate with respect to the catalytic machinery of the Nudix motif. These results suggest how the enzyme can catalyze the hydrolysis of a range of related dinucleoside tetraphosphate, but not triphosphate, compounds through precise orientation of key elements of the substrate.
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Affiliation(s)
- Scott Bailey
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, United Kingdom
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35
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Fletcher JI, Swarbrick JD, Maksel D, Gayler KR, Gooley PR. The structure of Ap(4)A hydrolase complexed with ATP-MgF(x) reveals the basis of substrate binding. Structure 2002; 10:205-13. [PMID: 11839306 DOI: 10.1016/s0969-2126(02)00696-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ap(4)A hydrolases are Nudix enzymes that regulate intracellular dinucleoside polyphosphate concentrations, implicating them in a range of biological events, including heat shock and metabolic stress. We have demonstrated that ATP x MgF(x) can be used to mimic substrates in the binding site of Ap(4)A hydrolase from Lupinus angustifolius and that, unlike previous substrate analogs, it is in slow exchange with the enzyme. The three-dimensional structure of the enzyme complexed with ATP x MgF(x) was solved and shows significant conformational changes. The substrate binding site of L. angustifolius Ap(4)A hydrolase differs markedly from the two previously published Nudix enzymes, ADP-ribose pyrophosphatase and MutT, despite their common fold and the conservation of active site residues. The majority of residues involved in substrate binding are conserved in asymmetrical Ap(4)A hydrolases from pathogenic bacteria, but are absent in their human counterparts, suggesting that it might be possible to generate compounds that target bacterial, but not human, Ap(4)A hydrolases.
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Affiliation(s)
- Jamie I Fletcher
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Victoria 3010, Australia
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36
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Abdelghany HM, Gasmi L, Cartwright JL, Bailey S, Rafferty JB, McLennan AG. Cloning, characterisation and crystallisation of a diadenosine 5',5"'-P(1),P(4)-tetraphosphate pyrophosphohydrolase from Caenorhabditis elegans. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1550:27-36. [PMID: 11738085 DOI: 10.1016/s0167-4838(01)00263-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Asymmetrically cleaving diadenosine 5',5"'-P(1),P(4)-tetraphosphate (Ap4A) hydrolase activity has been detected in extracts of adult Caenorhabditis elegans and the corresponding cDNA amplified and expressed in Escherichia coli. As expected, sequence analysis shows the enzyme to be a member of the Nudix hydrolase family. The purified recombinant enzyme behaves as a typical animal Ap4A hydrolase. It hydrolyses Ap4A with a K(m) of 7 microM and k(cat) of 27 s(-1) producing AMP and ATP as products. It is also active towards other adenosine and diadenosine polyphosphates with four or more phosphate groups, but not diadenosine triphosphate, always generating ATP as one of the products. It is inhibited non-competitively by fluoride (K(i)=25 microM) and competitively by adenosine 5'-tetraphosphate with Ap4A as substrate (K(i)=10 nM). Crystals of diffraction quality with the morphology of rectangular plates were readily obtained and preliminary data collected. These crystals diffract to a minimum d-spacing of 2 A and belong to either space group C222 or C222(1). Phylogenetic analysis of known and putative Ap4A hydrolases of the Nudix family suggests that they fall into two groups comprising plant and Proteobacterial enzymes on the one hand and animal and archaeal enzymes on the other. Complete structural determination of the C. elegans Ap4A hydrolase will help determine the basis of this grouping.
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Affiliation(s)
- H M Abdelghany
- School of Biological Sciences, University of Liverpool, UK
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37
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Bessman MJ, Walsh JD, Dunn CA, Swaminathan J, Weldon JE, Shen J. The gene ygdP, associated with the invasiveness of Escherichia coli K1, designates a Nudix hydrolase, Orf176, active on adenosine (5')-pentaphospho-(5')-adenosine (Ap5A). J Biol Chem 2001; 276:37834-8. [PMID: 11479323 DOI: 10.1074/jbc.m107032200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ygdP, a gene associated with the invasion of brain microvascular endothelial cells by Escherichia coli K1 (Badger, J. L., Wass, C. A., and Kim, K. S. (2000) Mol. Microbiol. 36, 174-182), the primary Gram-negative bacterium causing meningitis in newborns, has been cloned and expressed in E. coli. The protein, YgdP, was purified to near homogeneity and identified as a member of the Nudix hydrolase subfamily of dinucleoside oligophosphate pyrophosphatases. It catalyzes the hydrolysis of diadenosine tetra-, penta-, and hexa-phosphates with a preference for diadenosine penta-phosphate, from which it forms ATP and ADP. The enzyme has a requirement for a divalent metal cation that can be met with Mg2+, Zn2+, or Mn2+ and, like most of the Nudix hydrolases, has an alkaline pH optimum between 8.5 and 9. This is the second identification of a gene associated with the invasiveness of a human pathogen as a member of the Nudix hydrolase subfamily of dinucleoside oligophosphate pyrophosphatases, and an examination of homologous proteins in other invasive bacteria suggests that this may be a common feature of cellular invasion.
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Affiliation(s)
- M J Bessman
- Department of Biology and the McCollum-Pratt Institute, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
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38
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Maksel D, Gooley PR, Swarbrick JD, Guranowski A, Gange C, Blackburn GM, Gayler KR. Characterization of active-site residues in diadenosine tetraphosphate hydrolase from Lupinus angustifolius. Biochem J 2001; 357:399-405. [PMID: 11439089 PMCID: PMC1221966 DOI: 10.1042/0264-6021:3570399] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Site-directed mutagenesis has been used to characterize the functions of key amino acid residues in the catalytic site of the 'nudix' hydrolase, (asymmetrical) diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A) hydrolase (EC 3.6.1.17) from Lupinus angustifolius, the three-dimensional solution structure of which has recently been solved. Residues within the nudix motif, Gly-(Xaa)5-Glu-(Xaa)7-Arg-Glu-Uaa-Xaa-(Glu)2-Xaa-Gly (where Xaa represents unspecified amino acids and Uaa represents the bulky aliphatic amino acids Ile, Leu or Val) conserved in 'nudix enzymes', and residues important for catalysis from elsewhere in the molecule, were mutated and the expressed proteins characterized. The results reveal a high degree of functional conservation between lupin asymmetric Ap4A hydrolase and the 8-oxo-dGTP hydrolase from Escherichia coli. Charged residues in positions equivalent to those that ligate an enzyme-bound metal ion in the E. coli 8-oxo-dGTP hydrolase [Harris, Wu, Massiah and Mildvan (2000) Biochemistry 39, 1655-1674] were shown to contribute to catalysis to similar extents in the lupin enzyme. Mutations E55Q, E59Q and E125Q all reduced kcat markedly, whereas mutations R54Q, E58Q and E122Q had smaller effects. None of the mutations produced a substantial change in the Km)for Ap4A, but several extensively modified the pH-dependence and fluoride-sensitivities of the hydrolase. It was concluded that the precisely positioned glutamate residues Glu-55, Glu-59 and Glu-125 are conserved as functionally significant components of the hydrolytic mechanism in both of these members of the nudix family of hydrolases.
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Affiliation(s)
- D Maksel
- Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria 3010, Australia
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39
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Metzler DE, Metzler CM, Sauke DJ. Ribosomes and the Synthesis of Proteins. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50032-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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