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Romanov RS, Kurilova SA, Baykov AA, Rodina EV. Effect of Structure Variations in the Inter-subunit Contact Zone on the Activity and Allosteric Regulation of Inorganic Pyrophosphatase from Mycobacterium tuberculosis. BIOCHEMISTRY (MOSCOW) 2021; 85:326-333. [PMID: 32564737 DOI: 10.1134/s0006297920030086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Hexameric inorganic pyrophosphatase from Mycobacterium tuberculosis (Mt-PPase) has a number of structural and functional features that distinguish it from homologous enzymes widely occurring in living organisms. In particular, it has unusual zones of inter-subunit contacts and lacks the N-terminal region common for other PPases. In this work, we constructed two mutant forms of the enzyme, Ec-Mt-PPase and R14Q-Mt-PPase. In Ec-Mt-PPase, the missing part of the polypeptide chain was compensated with a fragment of PPase from Escherichia coli (Ec-PPase). In R14Q-Mt-PPase, a point mutation was introduced to the contact interface between the two trimers of the hexamer. Both modifications significantly improved the catalytic activity of the enzyme and abolished its inhibition by the cofactor (Mg2+ ion) excess. Activation of Mt-PPase by low (~10 μM) concentrations of ATP, fructose-1-phosphate, L-malate, and non-hydrolyzable substrate analogue methylene bisphosphonate (PCP) was observed. At concentrations of 100 μM and higher, the first three compounds acted as inhibitors. The activating effect of PCP was absent in both mutant forms, and the inhibitory effect of fructose-1-phosphate was absent in Ec-Mt-PPase. The effects of other modulators varied only quantitatively among the mutants. The obtained data indicate the presence of allosteric sites in Mt-PPase, which are located in the zones of inter-subunit contact or associated with them.
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Affiliation(s)
- R S Romanov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - S A Kurilova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - A A Baykov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - E V Rodina
- Lomonosov Moscow State University, Faculty of Chemistry, Moscow, 119991, Russia.
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2
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Romanov RS, Mariasina SS, Efimov SV, Klochkov VV, Rodina EV, Polshakov VI. Backbone resonance assignment and dynamics of 110 kDa hexameric inorganic pyrophosphatase from Mycobacterium tuberculosis. BIOMOLECULAR NMR ASSIGNMENTS 2020; 14:281-287. [PMID: 32562252 DOI: 10.1007/s12104-020-09962-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 06/17/2020] [Indexed: 06/11/2023]
Abstract
Family I soluble inorganic pyrophosphatases (PPases; EC 3.6.1.1) are enzymes essential for all organisms. They hydrolyze inorganic pyrophosphate, thus providing the driving force for numerous biosynthetic reactions. Soluble PPases retain enzymatic activity only in multimeric forms. PPases from various organisms are extensively studied by X-ray crystallography but until now there was no information on their structure and dynamics in solution. Hexameric 110 kDa (6 × 18.3 kDa) PPase from Mycobacterium tuberculosis (Mt-PPase) is a promising target for the rational design of potential anti-tuberculosis agents. In order to use NMR techniques in functional studies of Mt-PPase and rational design of the inhibitors for this enzyme, it is necessary to have information on the backbone 1H, 13C and 15N resonance assignments. Samples of Mt-PPase enriched with 99% of 13C and 15N isotopes, and 95% of 2H were obtained using recombinant protein expression in an isotopically-labeled medium and effective heat-shock protocol for the deuterium-to-hydrogen exchange of the amide groups. Backbone resonance assignment was achieved for more than 95% of the residues. It was found that the secondary structure of Mt-PPase in solution corresponds well to the crystal structure of this protein. Protein backbone dynamics were studied using 15N NMR relaxation experiments. Determined resonance assignments and dynamic properties provide the basis for the subsequent structure-based design of novel inhibitors of Mt-PPase-potential anti-tuberculosis drugs.
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Affiliation(s)
- Roman S Romanov
- Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow, Russia, 119991
| | - Sofia S Mariasina
- Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow, Russia, 119991
| | - Sergey V Efimov
- NMR Laboratory, Institute of Physics, Kazan Federal University, 18 Kremlevskaya St., Kazan, Russia, 420008
| | - Vladimir V Klochkov
- NMR Laboratory, Institute of Physics, Kazan Federal University, 18 Kremlevskaya St., Kazan, Russia, 420008
| | - Elena V Rodina
- Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow, Russia, 119991
| | - Vladimir I Polshakov
- Center for Magnetic Tomography and Spectroscopy, Faculty of Fundamental Medicine, M.V. Lomonosov Moscow State University, 119991, Moscow, Russia.
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Valueva A, Romanov RS, Mariasina SS, Eliseev MS, Rodina EV. Inorganic Pyrophosphatase-Nanodiamond Conjugates Hydrolyze Pyrophosphate in Human Synovial Fluid. ACS OMEGA 2020; 5:8579-8586. [PMID: 32337420 PMCID: PMC7178341 DOI: 10.1021/acsomega.9b04429] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 03/25/2020] [Indexed: 05/15/2023]
Abstract
The present work is focused on testing enzyme-based agents for the partial dissolution of calcium pyrophosphate (CaPPi) deposits in the cartilages and synovial fluid of patients with pyrophosphate arthropathy (CPPD disease). Previously, we suggested that inorganic pyrophosphatases (PPases) immobilized on nanodiamonds of detonation synthesis (NDs) could be appropriate for this purpose. We synthesized and characterized conjugates of NDs and PPases from Escherichia coli and Mycobacterium tuberculosis. The conjugates showed high enzymatic activity and resistance to inhibition by calcium and fluoride. Here, we tested the effectiveness of pyrophosphate (PPi) hydrolysis by the conjugates in an in vitro model system simulating the ionic composition of the synovial fluid and in the samples of synovial fluid of patients with CPPD via NMR spectroscopy. The conjugates of both PPases efficiently hydrolyzed triclinic crystalline calcium pyrophosphate (t-CPPD) in the model system. We evaluated the number of phosphorus-containing compounds in the synovial fluid, showed the possibility of PPi detection in it, and estimated the hydrolytic activity of the PPase conjugates. The soluble and immobilized PPases were able to hydrolyze a significant amount of PPi (1 mM) in the synovial fluid in short periods of time (24 h). The maximum activity was demonstrated for Mt-PPase immobilized on ND-NH-(CH2)6-NH2 (2.24 U mg-1).
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Affiliation(s)
- Anastasiya
V. Valueva
- Pharmaceutical
Department, Pavlov Ryazan State Medical
University, 9 Vysokovol’tnaya
Street, Ryazan 390026, Russia
| | - Roman S. Romanov
- Department
of Fundamental Medicine, Lomonosov Moscow
State University, 31, Building 5, Lomonosovsky Prospect, Moscow 119991, Russia
| | - Sofia S. Mariasina
- Department
of Fundamental Medicine, Lomonosov Moscow
State University, 31, Building 5, Lomonosovsky Prospect, Moscow 119991, Russia
| | - Maxim S. Eliseev
- V.A.
Nasonova Research Institute of Rheumatology, Kaschirskoe h. 34A, Moscow 115522, Russia
| | - Elena V. Rodina
- Chemistry
Department, Lomonosov Moscow State University, 1, Building 3, Leninskie Gory, Moscow 119992, Russia
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Valueva A, Romanov RS, Vorobyeva NN, Kurilova SA, Rodina EV. Synthesis of Inorganic Pyrophosphatase-Nanodiamond Conjugates Resistant to Calcium and Fluoride. ACS OMEGA 2020; 5:6641-6650. [PMID: 32258899 PMCID: PMC7114608 DOI: 10.1021/acsomega.9b04428] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 03/04/2020] [Indexed: 05/15/2023]
Abstract
Pyrophosphate arthropathy is the mineralization defect in humans caused by the deposition of microcrystals of calcium pyrophosphate dihydrate in joint tissues. As a potential therapeutic strategy for the treatment of pyrophosphate arthropathy, delivery of exogenous pyrophosphate-hydrolyzing enzymes, inorganic pyrophosphatases (PPases), to the synovial fluid has been suggested. Previously, we synthesized the conjugates of Escherichia coli PPase (Ec-PPase) with detonation synthesis nanodiamonds (NDs) as a delivery platform, obtaining the hybrid biomaterial retaining high pyrophosphate-hydrolyzing activity in vitro. However, most known PPases including Ec-PPase in the soluble form are strongly inhibited by Ca2+ ions. Because synovial fluid contains up to millimolar concentrations of soluble calcium, this inhibition might limit the in vivo application of Ec-PPase-based material in joint tissues. In this work, we proposed other bacterial PPases from Mycobacterium tuberculosis (Mt-PPase), which are resistant to the inhibition by Ca2+ ions, as an active PPi-hydrolyzing agent. We synthesized conjugates of Mt-PPase with NDs and tested their activity under various conditions. Unexpectedly, conjugates of both Ec-PPase and Mt-PPase with aminated NDs retained significant hydrolytic activity in the presence of well-known mechanism-based PPase inhibitors, fluoride or calcium. The incomplete inhibition of PPases by fluoride or calcium was found for the first time.
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Affiliation(s)
- Anastasiya
V. Valueva
- Pharmaceutical
Department, Pavlov Ryazan State Medical
University, 9 Vysokovol’tnaya
Street, Ryazan 390026, Russia
| | - Roman S. Romanov
- Department
of Fundamental Medicine, Lomonosov Moscow
State University, 31, Build. 5, Lomonosovsky Prospect, Moscow 119991, Russia
| | - Nataliya N. Vorobyeva
- Chemistry
Department, Lomonosov Moscow State University, 1, Build. 3, Leninskie Gory, Moscow 119992, Russia
| | - Svetlana A. Kurilova
- A.N.
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 1, Build. 40, Leninskie Gory, Moscow 119992, Russia
| | - Elena V. Rodina
- Chemistry
Department, Lomonosov Moscow State University, 1, Build. 3, Leninskie Gory, Moscow 119992, Russia
- E-mail:
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Kim WS, Kim JS, Cha SB, Kim H, Kwon KW, Kim SJ, Han SJ, Choi SY, Cho SN, Park JH, Shin SJ. Mycobacterium tuberculosis Rv3628 drives Th1-type T cell immunity via TLR2-mediated activation of dendritic cells and displays vaccine potential against the hyper-virulent Beijing K strain. Oncotarget 2018; 7:24962-82. [PMID: 27097115 PMCID: PMC5041883 DOI: 10.18632/oncotarget.8771] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 04/06/2016] [Indexed: 12/30/2022] Open
Abstract
Identification of vaccine target antigens (Ags) that induce Ag-specific Th1 immunity is the first step toward the development of a tuberculosis vaccine. Here, we evaluated the Mycobacterium tuberculosis (Mtb) protein Rv3628, a soluble inorganic pyrophosphatase, as a vaccine target and characterized the molecular details of its interaction with dendritic cells (DCs). Rv3628 activated DCs, increasing their expression of cell surface molecules and augmenting their production of TNF-α, IL-1β, IL-6, and IL-12p70. Rv3628 mediated these effects by binding to TLR2 and activating downstream MyD88-, MAPK- and NF-κB-dependent signaling pathways. Rv3628-stimulated DCs induced the expansion of OVA-specific CD4+ and CD8+ T cells, which secreted IFN-γ and IL-2. Rv3628-specific effector/memory T cells expanded to a similar extent as those stimulated with ESAT-6 Ag in samples of lung and spleen cells collected from Mtb-infected mice. Finally, an Rv3628 subunit vaccine adjuvanted with dimethyldioctadecylammonium liposomes containing monophosphoryl lipid-A caused significant reductions in bacterial counts and lung inflammation after challenge with the hyper-virulent Mtb K strain. Importantly, protective efficacy was correlated with the generation of Rv3628-specific CD4+ T cells co-producing IFN-γ, TNF-α and IL-2 and exhibiting an elevated IFN-γ recall response. Thus, Rv3628 polarizes DCs toward a Th1 phenotype and promotes protective immunity against Mtb infection.
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Affiliation(s)
- Woo Sik Kim
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Jong-Seok Kim
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Seung Bin Cha
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Hongmin Kim
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Kee Woong Kwon
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - So Jeong Kim
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Seung Jung Han
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Soo Young Choi
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Sang-Nae Cho
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - Jong-Hwan Park
- Laboratory of Animal Medicine, College of Veterinary Medicine, Chonnam National University, Gwangju, South Korea
| | - Sung Jae Shin
- Department of Microbiology, Institute for Immunology and Immunological Diseases, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
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Identification and characterization of an ecto-pyrophosphatase activity in intact epimastigotes of Trypanosoma rangeli. PLoS One 2014; 9:e106852. [PMID: 25203926 PMCID: PMC4159237 DOI: 10.1371/journal.pone.0106852] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2014] [Accepted: 08/09/2014] [Indexed: 02/06/2023] Open
Abstract
In this study, we performed the molecular and biochemical characterization of an ecto-enzyme present in Trypanosoma rangeli that is involved with the hydrolysis of extracellular inorganic pyrophosphate. PCR analysis identified a putative proton-pyrophosphatase (H+-PPase) in the epimastigote forms of T. rangeli. This protein was recognized with Western blot and flow cytometry analysis using an antibody against the H+-PPase of Arabidopsis thaliana. Immunofluorescence microscopy confirmed that this protein is located in the plasma membrane of T. rangeli. Biochemical assays revealed that the optimum pH for the ecto-PPase activity was 7.5, as previously demonstrated for other organisms. Sodium fluoride (NaF) and aminomethylenediphosphonate (AMDP) were able to inhibit approximately 75% and 90% of the ecto-PPase activity, respectively. This ecto-PPase activity was stimulated in a dose-dependent manner by MgCl2. In the presence of MgCl2, this activity was inhibited by millimolar concentrations of CaCl2. The ecto-PPase activity of T. rangeli decreased with increasing cell proliferation in vitro, thereby suggesting a role for this enzyme in the acquisition of inorganic phosphate (Pi). Moreover, this activity was modulated by the extracellular concentration of Pi and increased approximately two-fold when the cells were maintained in culture medium depleted of Pi. All of these results confirmed the occurrence of an ecto-PPase located in the plasma membrane of T. rangeli that possibly plays an important role in phosphate metabolism of this protozoan.
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Lv W, Banerjee B, Molland KL, Seleem MN, Ghafoor A, Hamed MI, Wan B, Franzblau SG, Mesecar AD, Cushman M. Synthesis of 3-(3-aryl-pyrrolidin-1-yl)-5-aryl-1,2,4-triazines that have antibacterial activity and also inhibit inorganic pyrophosphatase. Bioorg Med Chem 2014; 22:406-18. [PMID: 24315189 PMCID: PMC3914758 DOI: 10.1016/j.bmc.2013.11.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 10/23/2013] [Accepted: 11/05/2013] [Indexed: 11/26/2022]
Abstract
Inorganic pyrophosphatases are potential targets for the development of novel antibacterial agents. A pyrophosphatase-coupled high-throughput screening assay intended to detect o-succinyl benzoic acid coenzyme A (OSB CoA) synthetase inhibitors led to the unexpected discovery of a new series of novel inorganic pyrophosphatase inhibitors. Lead optimization studies resulted in a series of 3-(3-aryl-pyrrolidin-1-yl)-5-aryl-1,2,4-triazine derivatives that were prepared by an efficient synthetic pathway. One of the tetracyclic triazine analogues 22h displayed promising antibiotic activity against a wide variety of drug-resistant Staphylococcus aureus strains, as well as activity versus Mycobacterium tuberculosis and Bacillus anthracis, at a concentration that was not cytotoxic to mammalian cells.
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Affiliation(s)
- Wei Lv
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy and The Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907, United States
| | - Biplab Banerjee
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy and The Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907, United States
| | - Katrina L Molland
- Department of Biological Sciences and The Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907, United States
| | - Mohamed N Seleem
- Department of Comparative Pathobiology, Purdue University College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, United States
| | - Adil Ghafoor
- Department of Comparative Pathobiology, Purdue University College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, United States
| | - Maha I Hamed
- Department of Comparative Pathobiology, Purdue University College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, United States
| | - Baojie Wan
- Institute for Tuberculosis Research, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, United States
| | - Scott G Franzblau
- Institute for Tuberculosis Research, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, United States
| | - Andrew D Mesecar
- Department of Biological Sciences and The Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907, United States
| | - Mark Cushman
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy and The Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907, United States.
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Biswas T, Green KD, Garneau-Tsodikova S, Tsodikov OV. Discovery of inhibitors of Bacillus anthracis primase DnaG. Biochemistry 2013; 52:6905-10. [PMID: 24004110 DOI: 10.1021/bi4011286] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Primase DnaG is an essential bacterial enzyme that synthesizes short ribonucleotide primers required for chromosomal DNA replication. Inhibitors of DnaG can serve as leads for development of new antibacterials and biochemical probes. We recently developed a nonradioactive in vitro primase-pyrophosphatase assay to identify and analyze DnaG inhibitors. Application of this assay to DnaG from Bacillus anthracis (Ba DnaG), a dangerous pathogen, yielded several inhibitors, which include agents with DNA intercalating properties (doxorubicin and tilorone) as well as those that do not intercalate into DNA (suramin). A polyanionic agent and inhibitor of eukaryotic primases, suramin, identified by this assay as a low-micromolar Ba DnaG inhibitor, was recently shown to be also a low-micromolar inhibitor of Mycobacterium tuberculosis DnaG (Mtb DnaG). In contrast, another low-micromolar Ba DnaG inhibitor, tilorone, is much more potent against Ba DnaG than against Mtb DnaG, despite homology between these enzymes, suggesting that DnaG can be targeted selectively.
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Affiliation(s)
- Tapan Biswas
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan , Ann Arbor, Michigan 48109, United States
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Benini S, Wilson K. Structure of the Mycobacterium tuberculosis soluble inorganic pyrophosphatase Rv3628 at pH 7.0. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:866-70. [PMID: 21821883 PMCID: PMC3151116 DOI: 10.1107/s1744309111023323] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Accepted: 06/15/2011] [Indexed: 11/10/2022]
Abstract
The 1.5 Å resolution crystal structure of the Mycobacterium tuberculosis soluble inorganic pyrophosphatase Rv3628 at pH 7.0 is reported. The M. tuberculosis and M. leprae genomes include genes for the only two family I inorganic pyrophosphatases known to contain two histidines in the active site. The role of these two residues in catalysis is not fully understood. Mutational and functional studies of the M. tuberculosis enzyme showed that His21 and His86 are not essential for pyrophosphate hydrolysis, but are responsible for a shift in the optimal pH for the reaction compared with the Escherichia coli enzyme. Comparison with the structure previously reported at pH 5.0 provides further insight into the role of the two histidines. Two potassium-binding sites are found as a result of the high potassium concentration in the mother liquor.
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Affiliation(s)
- Stefano Benini
- Faculty of Science and Technology, Free University of Bolzano, Bolzano, Italy.
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Rodina EV, Samygina VR, Vorobyeva NN, Sitnik TS, Kurilova SA, Nazarova TI. Structural and kinetic features of family I inorganic pyrophosphatase from Vibrio cholerae. BIOCHEMISTRY. BIOKHIMIIA 2009; 74:734-742. [PMID: 19747093 DOI: 10.1134/s0006297909070050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this paper, kinetic properties of a soluble inorganic pyrophosphatase of family I from Vibrio cholerae (V-PPase), intestinal pathogen and causative agent of human cholera, are characterized in detail, and the crystal structure of a metal-free enzyme is reported. Hydrolytic activity of V-PPase has been studied as a function of pH, concentration of metal cofactors (Mg2+ or Mn2+), and ionic strength. It has been found that, despite the high conservation of amino acid sequences for the known bacterial PPases of family I, V-PPase differs from the other enzymes of the same family in a number of parameters. Dissociation constants of V-PPase complexed with Mg2+ or Mn2+ were essentially the same as for Escherichia coli PPase (E-PPase). However, the pH optimum of MgPP(i) hydrolysis by V-PPase was shifted to more alkaline pH due to higher values of the pK(a) of ionizable groups for both the free enzyme and the enzyme-substrate complex. The stability of a hexameric form of V-PPase has been studied as a function of pH. The corresponding pK(a) of a group that controls the stability of the hexamer at pH below 6 (pK(a) = 4.4) was significantly lower than in the other hexameric PPases. The crystal structure reported here is analyzed and compared with the structure of E-PPase. The location of amino acid residues that differ in V-PPase and E-PPase is discussed. Since V-PPase has been found to retain its hydrolytic activity in high ionic strength media, the observed structural and kinetic features are analyzed in view of the possible osmoadaptation of this protein.
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Affiliation(s)
- E V Rodina
- Chemistry Faculty, Lomonosov Moscow State University, Moscow, 119992, Russia.
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