1
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Bexkens ML, Martin OMF, van den Heuvel JM, Schmitz MGJ, Teusink B, Bakker BM, van Hellemond JJ, Haanstra JR, Walkinshaw MD, Tielens AGM. The unusual kinetics of lactate dehydrogenase of Schistosoma mansoni and their role in the rapid metabolic switch after penetration of the mammalian host. Int J Parasitol 2024; 54:367-378. [PMID: 38492780 DOI: 10.1016/j.ijpara.2024.03.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 01/24/2024] [Accepted: 03/11/2024] [Indexed: 03/18/2024]
Abstract
Lactate dehydrogenase (LDH) from Schistosoma mansoni has peculiar properties for a eukaryotic LDH. Schistosomal LDH (SmLDH) isolated from schistosomes, and the recombinantly expressed protein, are strongly inhibited by ATP, which is neutralized by fructose-1,6-bisphosphate (FBP). In the conserved FBP/anion binding site we identified two residues in SmLDH (Val187 and Tyr190) that differ from the conserved residues in LDHs of other eukaryotes, but are identical to conserved residues in FBP-sensitive prokaryotic LDHs. Three-dimensional (3D) models were generated to compare the structure of SmLDH with other LDHs. These models indicated that residues Val187, and especially Tyr190, play a crucial role in the interaction of FBP with the anion pocket of SmLDH. These 3D models of SmLDH are also consistent with a competitive model of SmLDH inhibition in which ATP (inhibitor) and FBP (activator) compete for binding in a well-defined anion pocket. The model of bound ATP predicts a distortion of the nearby key catalytic residue His195, resulting in enzyme inhibition. To investigate a possible physiological role of this allosteric regulation of LDH in schistosomes we made a kinetic model in which the allosteric regulation of the glycolytic enzymes can be varied. The model showed that inhibition of LDH by ATP prevents fermentation to lactate in the free-living stages in water and ensures complete oxidation via the Krebs cycle of the endogenous glycogen reserves. This mechanism of allosteric inhibition by ATP prevents the untimely depletion of these glycogen reserves, the only fuel of the free-living cercariae. Neutralization by FBP of this ATP inhibition of LDH prevents accumulation of glycolytic intermediates when S. mansoni schistosomula are confronted with the sudden large increase in glucose availability upon penetration of the final host. It appears that the LDH of S. mansoni is special and well suited to deal with the variations in glucose availability the parasite encounters during its life cycle.
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Affiliation(s)
- Michiel L Bexkens
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, The Netherlands
| | - Olivier M F Martin
- Systems Biology Lab, AIMMS, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Jos M van den Heuvel
- Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Marion G J Schmitz
- Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Bas Teusink
- Systems Biology Lab, AIMMS, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Barbara M Bakker
- Systems Biology Lab, AIMMS, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands; Laboratory of Pediatrics, Systems Medicine of Metabolism and Signaling, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Jaap J van Hellemond
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, The Netherlands
| | - Jurgen R Haanstra
- Systems Biology Lab, AIMMS, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Malcolm D Walkinshaw
- Wellcome Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom
| | - Aloysius G M Tielens
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC University Medical Center, Rotterdam, The Netherlands; Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
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2
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Robin AY, Brochier-Armanet C, Bertrand Q, Barette C, Girard E, Madern D. Deciphering Evolutionary Trajectories of Lactate Dehydrogenases Provides New Insights into Allostery. Mol Biol Evol 2023; 40:msad223. [PMID: 37797308 PMCID: PMC10583557 DOI: 10.1093/molbev/msad223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/22/2023] [Accepted: 09/28/2023] [Indexed: 10/07/2023] Open
Abstract
Lactate dehydrogenase (LDH, EC.1.1.127) is an important enzyme engaged in the anaerobic metabolism of cells, catalyzing the conversion of pyruvate to lactate and NADH to NAD+. LDH is a relevant enzyme to investigate structure-function relationships. The present work provides the missing link in our understanding of the evolution of LDHs. This allows to explain (i) the various evolutionary origins of LDHs in eukaryotic cells and their further diversification and (ii) subtle phenotypic modifications with respect to their regulation capacity. We identified a group of cyanobacterial LDHs displaying eukaryotic-like LDH sequence features. The biochemical and structural characterization of Cyanobacterium aponinum LDH, taken as representative, unexpectedly revealed that it displays homotropic and heterotropic activation, typical of an allosteric enzyme, whereas it harbors a long N-terminal extension, a structural feature considered responsible for the lack of allosteric capacity in eukaryotic LDHs. Its crystallographic structure was solved in 2 different configurations typical of the R-active and T-inactive states encountered in allosteric LDHs. Structural comparisons coupled with our evolutionary analyses helped to identify 2 amino acid positions that could have had a major role in the attenuation and extinction of the allosteric activation in eukaryotic LDHs rather than the presence of the N-terminal extension. We tested this hypothesis by site-directed mutagenesis. The resulting C. aponinum LDH mutants displayed reduced allosteric capacity mimicking those encountered in plants and human LDHs. This study provides a new evolutionary scenario of LDHs that unifies descriptions of regulatory properties with structural and mutational patterns of these important enzymes.
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Affiliation(s)
- Adeline Y Robin
- Université Grenoble Alpes, CNRS, CEA, IBS, F-38000 Grenoble, France
| | - Céline Brochier-Armanet
- Laboratoire de Biométrie et Biologie Évolutive, Université Claude Bernard Lyon 1, CNRS, UMR5558, Villeurbanne F-69622, France
| | - Quentin Bertrand
- Université Grenoble Alpes, CNRS, CEA, IBS, F-38000 Grenoble, France
- Laboratory of Biomolecular Research, Biology and Chemistry Division, Paul Scherrer Institut, Villigen, Switzerland
| | - Caroline Barette
- Université Grenoble Alpes, CEA, Inserm, IRIG, BGE, Grenoble 38000, France
| | - Eric Girard
- Université Grenoble Alpes, CNRS, CEA, IBS, F-38000 Grenoble, France
| | - Dominique Madern
- Université Grenoble Alpes, CNRS, CEA, IBS, F-38000 Grenoble, France
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3
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Allosteric transitions of rabbit skeletal muscle lactate dehydrogenase induced by pH-dependent dissociation of the tetrameric enzyme. Biochimie 2022; 199:23-35. [DOI: 10.1016/j.biochi.2022.03.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 02/23/2022] [Accepted: 03/25/2022] [Indexed: 02/04/2023]
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4
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Friberg A, Rehwinkel H, Nguyen D, Pütter V, Quanz M, Weiske J, Eberspächer U, Heisler I, Langer G. Structural Evidence for Isoform-Selective Allosteric Inhibition of Lactate Dehydrogenase A. ACS OMEGA 2020; 5:13034-13041. [PMID: 32548488 PMCID: PMC7288559 DOI: 10.1021/acsomega.0c00715] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 05/13/2020] [Indexed: 05/11/2023]
Abstract
Lactate dehydrogenase A (LDHA) is frequently overexpressed in tumors, thereby sustaining high glycolysis rates, tumor growth, and chemoresistance. High-throughput screening resulted in the identification of phthalimide and dibenzofuran derivatives as novel lactate dehydrogenase inhibitors, selectively inhibiting the activity of the LDHA isoenzyme. Cocrystallization experiments confirmed target engagement in addition to demonstrating binding to a novel allosteric binding site present in all four LDHA subunits of the LDH5 homotetramer.
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Affiliation(s)
- Anders Friberg
- Bayer AG,
Pharmaceuticals, R&D, Müllerstrasse 178, 13342 Berlin, Germany
- E-mail:
| | - Hartmut Rehwinkel
- Bayer AG,
Pharmaceuticals, R&D, Müllerstrasse 178, 13342 Berlin, Germany
| | - Duy Nguyen
- Bayer AG,
Pharmaceuticals, R&D, Müllerstrasse 178, 13342 Berlin, Germany
| | - Vera Pütter
- Bayer AG,
Pharmaceuticals, R&D, Müllerstrasse 178, 13342 Berlin, Germany
| | - Maria Quanz
- Bayer AG,
Pharmaceuticals, R&D, Müllerstrasse 178, 13342 Berlin, Germany
| | - Jörg Weiske
- Bayer AG,
Pharmaceuticals, R&D, Müllerstrasse 178, 13342 Berlin, Germany
| | - Uwe Eberspächer
- Bayer AG,
Pharmaceuticals, R&D, Müllerstrasse 178, 13342 Berlin, Germany
| | - Iring Heisler
- Bayer
AG, Pharmaceuticals, R&D, Aprather Weg 18A, 42113 Wuppertal, Germany
| | - Gernot Langer
- Bayer AG,
Pharmaceuticals, R&D, Müllerstrasse 178, 13342 Berlin, Germany
- E-mail:
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5
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Thirumalai D, Hyeon C, Zhuravlev PI, Lorimer GH. Symmetry, Rigidity, and Allosteric Signaling: From Monomeric Proteins to Molecular Machines. Chem Rev 2019; 119:6788-6821. [DOI: 10.1021/acs.chemrev.8b00760] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- D. Thirumalai
- Department of Chemistry, The University of Texas, Austin, Texas 78712, United States
| | - Changbong Hyeon
- Korea Institute for Advanced Study, Seoul 02455, Republic of Korea
| | - Pavel I. Zhuravlev
- Biophysics Program, Institute for Physical Science and Technology and Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
| | - George H. Lorimer
- Biophysics Program, Institute for Physical Science and Technology and Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
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6
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Chen J, Thirumalai D. Interface Residues That Drive Allosteric Transitions Also Control the Assembly of l-Lactate Dehydrogenase. J Phys Chem B 2018; 122:11195-11205. [PMID: 30102042 DOI: 10.1021/acs.jpcb.8b06430] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The allosteric enzyme, l-lactate dehydrogenase (LDH), is activated by fructose 1,6-metaphosphate (FBP) to reduce pyruvate to lactate. The molecular details of the FBP-driven transition from the low affinity T state to the high affinity R state in LDH, a tetramer composed of identical subunits, are not known. The dynamics of the T → R allosteric transition, investigated using Brownian dynamics (BD) simulations of the self-organized polymer (SOP) model, revealed that coordinated rotations of the subunits drive the T → R transition. We used the structural perturbation method (SPM), which requires only the static structure, to identify the allostery wiring diagram (AWD), a network of residues that transmits signals across the tetramer, as LDH undergoes the T → R transition. Interestingly, the residues that play a major role in the dynamics, which are predominantly localized at the interfaces, coincide with the AWD identified using the SPM. Although the allosteric pathways are highly heterogeneous, on the basis of our simulations, we surmise that predominantly the conformational changes in the T → R transition start from the region near the active site, comprised of helix αC, helix α1/2G, helix α3G, and helix α2F, and proceed to other structural units, thus completing the global motion. Brownian dynamics simulations of the tetramer assembly, triggered by a temperature quench from the fully disrupted conformations, show that the bottleneck for assembly is the formation of the correct orientational registry between the subunits, requiring contacts between the interface residues. Surprisingly, these residues are part of the AWD, which was identified using the SPM. Taken together, our results show that LDH, and perhaps other multidomain proteins, may have evolved to stabilize distinct states of allosteric enzymes using precisely the same AWD that also controls the functionally relevant allosteric transitions.
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Affiliation(s)
- Jie Chen
- Biophysics Program, Institute for Physical Science and Technology , University of Maryland , College Park , Maryland 20742 , United States
| | - D Thirumalai
- Department of Chemistry , The University of Texas , Austin , Texas 78712 , United States
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7
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Andrews BA, Dyer RB. Small molecule cores demonstrate non-competitive inhibition of lactate dehydrogenase. MEDCHEMCOMM 2018; 9:1369-1376. [PMID: 30151092 DOI: 10.1039/c8md00309b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 07/11/2018] [Indexed: 12/14/2022]
Abstract
Lactate dehydrogenase (LDH) has recently garnered attention as an attractive target for cancer therapies, owing to the enzyme's critical role in cellular metabolism. Current inhibition strategies, employing substrate or cofactor analogues, are insufficiently specific for use as pharmaceutical agents. The possibility of allosteric inhibition of LDH was postulated on the basis of theoretical docking studies of a small molecule inhibitor to LDH. The present study examined structural analogues of this proposed inhibitor to gauge its potency and attempt to elucidate the molecular mechanism of action. These analogues display encouraging in vitro inhibition of porcine heart LDH, including micromolar Ki values and a maximum inhibition of up to 50% in the steady state. Furthermore, Michaelis-Menten kinetics and fluorescence data both suggest the simple, acetaminophen derivatives are non-competitive in binding to the enzyme. Kinetic comparisons of a panel of increasingly decorated structural analogues imply that the binding is specific, and the small molecule core provides a privileged scaffold for further pharmaceutical development of a novel, allosteric drug.
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Affiliation(s)
- Brooke A Andrews
- Department of Chemistry , Emory University , Atlanta , 30322 , Georgia , USA .
| | - R Brian Dyer
- Department of Chemistry , Emory University , Atlanta , 30322 , Georgia , USA .
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8
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Comino N, Cifuente JO, Marina A, Orrantia A, Eguskiza A, Guerin ME. Mechanistic insights into the allosteric regulation of bacterial ADP-glucose pyrophosphorylases. J Biol Chem 2017; 292:6255-6268. [PMID: 28223362 DOI: 10.1074/jbc.m116.773408] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 02/17/2017] [Indexed: 11/06/2022] Open
Abstract
ADP-glucose pyrophosphorylase (AGPase) controls bacterial glycogen and plant starch biosynthetic pathways, the most common carbon storage polysaccharides in nature. AGPase activity is allosterically regulated by a series of metabolites in the energetic flux within the cell. Very recently, we reported the first crystal structures of the paradigmatic AGPase from Escherichia coli (EcAGPase) in complex with its preferred physiological negative and positive allosteric regulators, adenosine 5'-monophosphate (AMP) and fructose 1,6-bisphosphate (FBP), respectively. However, understanding the molecular mechanism by which AMP and FBP allosterically modulates EcAGPase enzymatic activity still remains enigmatic. Here we found that single point mutations of key residues in the AMP-binding site decrease its inhibitory effect but also clearly abolish the overall AMP-mediated stabilization effect in wild-type EcAGPase. Single point mutations of key residues for FBP binding did not revert the AMP-mediated stabilization. Strikingly, an EcAGPase-R130A mutant displayed a dramatic increase in activity when compared with wild-type EcAGPase, and this increase correlated with a significant increment of glycogen content in vivo The crystal structure of EcAGPase-R130A revealed unprecedented conformational changes in structural elements involved in the allosteric signal transmission. Altogether, we propose a model in which the positive and negative energy reporters regulate AGPase catalytic activity via intra- and interprotomer cross-talk, with a "sensory motif" and two loops, RL1 and RL2, flanking the ATP-binding site playing a significant role. The information reported herein provides exciting possibilities for industrial/biotechnological applications.
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Affiliation(s)
- Natalia Comino
- From the Structural Biology Unit, CIC bioGUNE, Bizkaia Technology Park, 48160 Derio, Spain
| | - Javier O Cifuente
- From the Structural Biology Unit, CIC bioGUNE, Bizkaia Technology Park, 48160 Derio, Spain
| | - Alberto Marina
- From the Structural Biology Unit, CIC bioGUNE, Bizkaia Technology Park, 48160 Derio, Spain
| | - Ane Orrantia
- From the Structural Biology Unit, CIC bioGUNE, Bizkaia Technology Park, 48160 Derio, Spain
| | - Ander Eguskiza
- From the Structural Biology Unit, CIC bioGUNE, Bizkaia Technology Park, 48160 Derio, Spain
| | - Marcelo E Guerin
- From the Structural Biology Unit, CIC bioGUNE, Bizkaia Technology Park, 48160 Derio, Spain, .,Unidad de Biofísica, Centro Mixto Consejo Superior de Investigaciones Científicas-Universidad del País Vasco/Euskal Herriko Unibertsitatea (CSIC,UPV/EHU), Barrio Sarriena s/n, Leioa, 48940 Bizkaia, Spain.,Departamento de Bioquímica, Universidad del País Vasco, Leioa, 48940 Bizkaia, Spain, and.,IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
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9
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Taguchi H. The Simple and Unique Allosteric Machinery of Thermus caldophilus Lactate Dehydrogenase. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 925:117-145. [DOI: 10.1007/5584_2016_171] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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10
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Ikehara Y, Arai K, Furukawa N, Ohno T, Miyake T, Fushinobu S, Nakajima M, Miyanaga A, Taguchi H. The core of allosteric motion in Thermus caldophilus L-lactate dehydrogenase. J Biol Chem 2014; 289:31550-64. [PMID: 25258319 DOI: 10.1074/jbc.m114.599092] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
For Thermus caldophilus L-lactate dehydrogenase (TcLDH), fructose 1,6-bisphosphate (FBP) reduced the pyruvate S(0.5) value 10(3)-fold and increased the V(max) value 4-fold at 30 °C and pH 7.0, indicating that TcLDH has a much more T state-sided allosteric equilibrium than Thermus thermophilus L-lactate dehydrogenase, which has only two amino acid replacements, A154G and H179Y. The inactive (T) and active (R) state structures of TcLDH were determined at 1.8 and 2.0 Å resolution, respectively. The structures indicated that two mobile regions, MR1 (positions 172-185) and MR2 (positions 211-221), form a compact core for allosteric motion, and His(179) of MR1 forms constitutive hydrogen bonds with MR2. The Q4(R) mutation, which comprises the L67E, H68D, E178K, and A235R replacements, increased V(max) 4-fold but reduced pyruvate S(0.5) only 5-fold in the reaction without FBP. In contrast, the P2 mutation, comprising the R173Q and R216L replacements, did not markedly increase V(max), but 10(2)-reduced pyruvate S(0.5), and additively increased the FBP-independent activity of the Q4(R) enzyme. The two types of mutation consistently increased the thermal stability of the enzyme. The MR1-MR2 area is a positively charged cluster, and its center approaches another positively charged cluster (N domain cluster) across the Q-axis subunit interface by 5 Å, when the enzyme undergoes the T to R transition. Structural and kinetic analyses thus revealed the simple and unique allosteric machinery of TcLDH, where the MR1-MR2 area pivotally moves during the allosteric motion and mediates the allosteric equilibrium through electrostatic repulsion within the protein molecule.
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Affiliation(s)
- Yoko Ikehara
- From the Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Kazuhito Arai
- From the Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Nayuta Furukawa
- From the Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Tadashi Ohno
- From the Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Tatsuya Miyake
- From the Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Shinya Fushinobu
- the Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan, and
| | - Masahiro Nakajima
- From the Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Akimasa Miyanaga
- the Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Hayao Taguchi
- From the Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan,
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Sobczak M, Boczek T, Kowalski A, Wiktorska M, Niewiarowska J, Zylinska L. Downregulation of microsomal glutathione-S-transferase 1 modulates protective mechanisms in differentiated PC12 cells. J Physiol Biochem 2014; 70:375-83. [PMID: 24419913 DOI: 10.1007/s13105-014-0312-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 01/01/2014] [Indexed: 12/12/2022]
Abstract
Microsomal glutathione-S-transferase 1 (Mgst1) plays a specific role in protection of cells against oxidative stress. In this study, we assayed the effect of Mgst1 downregulation on cells behavior using differentiated PC12 line, a widely accepted neuronal model system. We have developed stable transfected cells with downregulated Mgst1 (PC12_M), which were differentiated with 1 mM dibutyryl-cAMP (db-cAMP). Mgst1 reduction induced necrosis, decreased ATP amount, and increased thiobarbituric acid reacting substances (TBARS) content. However, in PC12_M cell population, we detected more intensive neuritogenesis than that in mock-transfected cells. Interestingly, total glutathione as well as GSH level were significantly higher than those in control PC12 line. Real-time PCR and Western blot analyses showed elevated expression of enzymes involved in glutathione metabolism-a rate-limiting γ-glutamylcysteine ligase and glutathione reductase. The present study shows for the first time that under stress conditions induced by Mgst1 downregulation, a rescue pathway can be activated and thereby enables differentiated PC12 cells to survive. Since Mgst1expression was reported to decline with age, our results could represent a putative adaptive process during aging. It could also be an early mechanism protecting neuronal cells against some neurodegenerative insults.
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Affiliation(s)
- Monika Sobczak
- Department of Molecular Neurochemistry, Medical University, 6/8 Mazowiecka Str., 92-215, Lodz, Poland
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12
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Arai K, Ichikawa J, Nonaka S, Miyanaga A, Uchikoba H, Fushinobu S, Taguchi H. A molecular design that stabilizes active state in bacterial allosteric L-lactate dehydrogenases. J Biochem 2011; 150:579-91. [PMID: 21828088 DOI: 10.1093/jb/mvr100] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
l-Lactate dehydrogenase (l-LDH) of Lactobacillus casei (LCLDH) is a typical bacterial allosteric l-LDH that requires fructose 1,6-bisphosphate (FBP) for its enzyme activity. A mutant LCLDH was designed to introduce an inter-subunit salt bridge network at the Q-axis subunit interface, mimicking Lactobacillus pentosus non-allosteric l-LDH (LPLDH). The mutant LCLDH exhibited high catalytic activity with hyperbolic pyruvate saturation curves independently of FBP, and virtually the equivalent K(m) and V(m) values at pH 5.0 to those of the fully activated wild-type enzyme with FBP, although the K(m) value was slightly improved with FBP or Mn(2+) at pH 7.0. The mutant enzyme exhibited a markedly higher apparent denaturating temperature (T(1/2)) than the wild-type enzyme in the presence of FBP, but showed an even lower T(1/2) without FBP, where it exhibited higher activation enthalpy of inactivation (ΔH(‡)). This result is consistent with the fact that the active state is more unstable than the inactive state in allosteric equilibrium of LCLDH. The LPLDH-like network appears to be conserved in many bacterial non-allosteric l-LDHs and dimeric l-malate dehydrogenases, and thus to be a key for the functional divergence of bacterial l-LDHs during evolution.
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Affiliation(s)
- Kazuhito Arai
- Department of Applied Biological Science, Tokyo University of Science, Noda, Chiba, Japan
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13
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Jers C, Pedersen MM, Paspaliari DK, Schütz W, Johnsson C, Soufi B, Macek B, Jensen PR, Mijakovic I. Bacillus subtilis BY-kinase PtkA controls enzyme activity and localization of its protein substrates. Mol Microbiol 2010; 77:287-99. [PMID: 20497499 DOI: 10.1111/j.1365-2958.2010.07227.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bacillus subtilis BY-kinase PtkA was previously shown to phosphorylate, and thereby regulate the activity of two classes of protein substrates: UDP-glucose dehydrogenases and single-stranded DNA-binding proteins. Our recent phosphoproteome study identified nine new tyrosine-phosphorylated proteins in B. subtilis. We found that the majority of these proteins could be phosphorylated by PtkA in vitro. Among these new substrates, single-stranded DNA exonuclease YorK, and aspartate semialdehyde dehydrogenase Asd were activated by PtkA-dependent phosphorylation. Because enzyme activity was not affected in other cases, we used fluorescent protein tags to study the impact of PtkA on localization of these proteins in vivo. For several substrates colocalization with PtkA was observed, and more importantly, the localization pattern of the proteins enolase, YjoA, YnfE, YvyG, Ugd and SsbA was dramatically altered in DeltaptkA background. Our results confirm that PtkA can control enzyme activity of its substrates in some cases, but also reveal a new mode of action for PtkA, namely ensuring correct cellular localization of its targets.
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Affiliation(s)
- Carsten Jers
- Micalis UMR 1319, AgroParisTech-INRA, Jouy-en-Josas, France
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14
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Arai K, Ishimitsu T, Fushinobu S, Uchikoba H, Matsuzawa H, Taguchi H. Active and inactive state structures of unliganded Lactobacillus casei allosteric L-lactate dehydrogenase. Proteins 2010; 78:681-94. [PMID: 19787773 DOI: 10.1002/prot.22597] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Lactobacillus casei L-lactate dehydrogenase (LCLDH) is activated through the homotropic and heterotropic activation effects of pyruvate and fructose 1,6-bisphosphate (FBP), respectively, and exhibits unusually high pH-dependence in the allosteric effects of these ligands. The active (R) and inactive (T) state structures of unliganded LCLDH were determined at 2.5 and 2.6 A resolution, respectively. In the catalytic site, the structural rearrangements are concerned mostly in switching of the orientation of Arg171 through the flexible intersubunit contact at the Q-axis subunit interface. The distorted orientation of Arg171 in the T state is stabilized by a unique intra-helix salt bridge between Arg171 and Glu178, which is in striking contrast to the multiple intersubunit salt bridges in Lactobacillus pentosus nonallosteric L-lactate dehydrogenase. In the backbone structure, major structural rearrangements of LCLDH are focused in two mobile regions of the catalytic domain. The two regions form an intersubunit linkage through contact at the P-axis subunit interface involving Arg185, replacement of which with Gln severely decreases the homotropic and hetertropic activation effects on the enzyme. These two regions form another intersubunit linkage in the Q-axis related dimer through the rigid NAD-binding domain, and thus constitute a pivotal frame of the intersubunit linkage for the allosteric motion, which is coupled with the concerted structural change of the four subunits in a tetramer, and of the binding sites for pyruvate and FBP. The unique intersubunit salt bridges, which are observed only in the R state structure, are likely involved in the pH-dependent allosteric equilibrium.
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Affiliation(s)
- Kazuhito Arai
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan
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Oh JH, Jung HK, Park YJ, Kim CK, Chung SY, Park NG, Yun YW, Kim DJ, Ha TY, Song YS, Lee YM, Oh KW, Hong JT. Inhibitory effects of ochratoxin A on nerve growth factor-induced neurite extension through downregulation of p38 MAP kinase and AP-1 activation in cultured pheochromocytoma cells. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2004; 67:357-371. [PMID: 14713565 DOI: 10.1080/15287390490273578] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Ochratoxin A (OTA) induces microcephaly in animals and in vitro cultured whole embryos. Inhibition of neuronal cell differentiation was proposed as underlying mechanisms responsible for OTA-induced microcephaly. Previously it was found that OTA inhibited differentiation of cultured rat embryonic midbrain cells into neurons. In this study, the influence of OTA on differentiation in PC-12 cells, a widely accepted model cells for study of neuronal differentiation was examined. Cell differentiation was assessed by measurement of neurite extension and quantified by the number of neurites extended. OTA decreased serum and nerve growth factor (NGF)-induced neurite extension in a concentration-dependent manner. Since MAP kinase and transcription factors have been implicated in cell differentiation of neuronal cells, and our previous study demonstrated that p38 MAP kinase and AP-1 are activated during PC 12 cell differentiation, the effect of OTA on NGF-induced p38 MAP kinase and transcription factor activation was examined. Co-treatment of OTA with NGF resulted in inhibition of NGF-induced p38 MAP kinase and AP-1 activation. Moreover, SB203580, a specific inhibitor of p38 MAP kinase blocked p38 MAP kinase and AP-1 activation accompanied by further inhibition of neurite extension. The present study shows that OTA inhibited cell differentiation of PC-12 cells, and this inhibitory effect may be related to inhibition of the activation of the p38 MAP kinase in conjunction with transcription factors AP-1. This finding suggests that the inhibitory effect on neuronal cell differentiation by OTA might be a mechanism responsible for OTA-induced microcephaly.
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Affiliation(s)
- Jae Ho Oh
- Korea Food and Drug Administration, Seoul, Korea
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17
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Nelson SW, Honzatko RB, Fromm HJ. Origin of cooperativity in the activation of fructose-1,6-bisphosphatase by Mg2+. J Biol Chem 2004; 279:18481-7. [PMID: 14978036 DOI: 10.1074/jbc.m308811200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fructose-1,6-bisphosphatase requires a divalent metal cation for catalysis, Mg(2+) being its most studied activator. Phosphatase activity increases sigmoidally with the concentration of Mg(2+), but the mechanistic basis for such cooperativity is unknown. Bound magnesium cations can interact within a single subunit or between different subunits of the enzyme tetramer. Mutations of Asp(118), Asp(121), or Glu(97) to alanine inactivate the recombinant porcine enzyme. These residues bind directly to magnesium cations at the active site. Three different hybrid tetramers of fructose-1,6-bisphosphatase, composed of one wild-type subunit and three subunits bearing one of the mutations above, exhibit kinetic parameters (K(m) for fructose-1,6-bisphosphate, 1.1-1.8 microm; K(a) for Mg(2+), 0.34-0.76 mm; K(i) for fructose-2,6-bisphosphate, 0.11-0.61 microm; and IC(50) for AMP, 3.8-7.4 microm) nearly identical to those of the wild-type enzyme. Notwithstanding these similarities, the k(cat) parameter for each hybrid tetramer is approximately one-fourth of that for the wild-type enzyme. Evidently, each subunit in the wild-type tetramer can independently achieve maximum velocity when activated by Mg(2+). Moreover, the activities of the three hybrid tetramers vary sigmoidally with the concentration of Mg(2+) (Hill coefficients of approximately 2). The findings above are fully consistent with a mechanism of cooperativity that arises from within a single subunit of fructose-1,6-bisphosphatase.
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Affiliation(s)
- Scott W Nelson
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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Grant GA, Hu Z, Xu XL. Hybrid tetramers reveal elements of cooperativity in Escherichia coli D-3-phosphoglycerate dehydrogenase. J Biol Chem 2003; 278:18170-6. [PMID: 12644455 DOI: 10.1074/jbc.m213050200] [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] [Indexed: 11/06/2022] Open
Abstract
d-3-Phosphoglycerate dehydrogenase from Escherichia coli is a tetramer of identical subunits that is inhibited when l-serine binds at allosteric sites between subunits. Co-expression of two genes, the native gene containing a charge difference mutation and a gene containing a mutation that eliminates serine binding, produces hybrid tetramers that can be separated by ion exchange chromatography. Activity in the hybrid tetramer with only a single intact serine binding site is inhibited by approximately 58% with a Hill coefficient of 1. Thus, interaction at a single regulatory domain interface does not, in itself, lead to the positive cooperativity of inhibition manifest in the native enzyme. Tetramers with only two intact serine binding sites purify as a mixture that displays a maximum inhibition level that is less than that of native enzyme, suggesting the presence of a population of tetramers that are unable to be fully inhibited. Differential analysis of this mixture supports the conclusion that it contains two forms of the tetramer. One form contains two intact serine binding sites at the same interface and is not fully inhibitable. The second form is a fully inhibitable population that has one serine binding site at each interface. Overall, the hybrid tetramers show that the positive cooperativity observed for serine binding is mediated across the nucleotide binding domain interface, and the negative cooperativity is mediated across the regulatory domain interface. That is, they reveal a pattern in which the binding of serine at one interface leads to negative cooperativity of binding of a subsequent serine at the same interface and positive cooperativity of binding of a subsequent serine to the opposite interface. This trend is propagated to subsequent binding sites in the tetramer such that the negative cooperativity that is originally manifest at one interface is decreased by subsequent binding of ligand at the opposite interface.
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Affiliation(s)
- Gregory A Grant
- Department of Molecular Biology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Abstract
Human immunodeficiency virus (HIV)-infected individuals are suffering from systemic oxidative stress. Reactive oxygen species act as second messengers for the activation of nuclear factor-kappaB (NF-kappaB), which augments the replication of HIV. Intracellular levels of glutathione (GSH), a major cytosolic antioxidant, in T cells decrease during the disease progression. Another redox-regulating molecule, thioredoxin (TRX), is also transiently down-regulated in the cells by acute HIV infection. In contrast, plasma levels of TRX are elevated in the late stage of HIV infection. Intracellular GSH and plasma TRX can be biomarkers to predict the prognosis of the disease. N-Acetylcysteine (NAC), a prodrug of cysteine that is necessary for GSH synthesis, has been used for HIV infection to prevent the activation of NF-kappaB and the replication of HIV. NAC shows some beneficial effects for HIV-infected individuals, although the intracellular GSH levels in lymphocytes are not significantly restored. The control of imbalanced redox status by antioxidants may be beneficial for the quality of life in HIV infection even in the era after the effective therapy with protease inhibitors has been applied. Redox control will be an important therapeutic strategy for oxidative stress-associated disorders including HIV infection.
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Affiliation(s)
- Hajime Nakamura
- Department of Biological Responses, Institute for Virus Research, Kyoto University, 53 Shogin-Kawaharacho, Sakyo, Kyoto 606-8507, Japan.
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Nelson SW, Honzatko RB, Fromm HJ. Hybrid tetramers of porcine liver fructose-1,6-bisphosphatase reveal multiple pathways of allosteric inhibition. J Biol Chem 2002; 277:15539-45. [PMID: 11854289 DOI: 10.1074/jbc.m112304200] [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: 11/06/2022] Open
Abstract
Fructose-1,6-bisphosphatase is a square planar tetramer of identical subunits, which exhibits cooperative allosteric inhibition of catalysis by AMP. Protocols for in vitro subunit exchange provide three of five possible hybrid tetramers of fructose-1,6-bisphosphatase in high purity. The two hybrid types with different subunits in the top and bottom halves of the tetramer co-purify. Hybrid tetramers, formed from subunits unable to bind AMP and subunits with wild-type properties, differ from the wild-type enzyme only in regard to their properties of AMP inhibition. Hybrid tetramers exhibit cooperative, potent, and complete (100%) AMP inhibition if at least one functional AMP binding site exists in the top and bottom halves of the tetramer. Furthermore, titrations of hybrid tetramers with AMP, monitored by a tryptophan reporter group, reveal cooperativity and fluorescence changes consistent with an R- to T-state transition, provided that again at least one functional AMP site exists in the top and bottom halves of the tetramer. In contrast, hybrid tetramers, which have functional AMP binding sites in only one half (top/bottom), exhibit an R- to T-state transition and complete AMP inhibition, but without cooperativity. Evidently, two pathways of allosteric inhibition of fructose-1,6-bisphosphatase are possible, only one of which is cooperative.
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Affiliation(s)
- Scott W Nelson
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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Uchikoba H, Fushinobu S, Wakagi T, Konno M, Taguchi H, Matsuzawa H. Crystal structure of non-allosteric L-lactate dehydrogenase from Lactobacillus pentosus at 2.3 A resolution: specific interactions at subunit interfaces. Proteins 2002; 46:206-14. [PMID: 11807949 DOI: 10.1002/prot.1165] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
L-Lactate dehydrogenase (LDH) from Lactobacillus pentosus is a non-allosteric enzyme, which shows, however, high sequence similarity to allosteric LDHs from certain bacteria. To elucidate the structural basis of the absence of allostery of L. pentosus LDH (LPLDH), we determined the crystal structure of LPLDH at 2.3 A resolution. Bacterial LDHs are tetrameric enzymes composed of identical subunits and exhibit 222 symmetry. The quaternary structure of LPLDH was similar to the active conformation of allosteric LDHs. Structural analysis revealed that the subunit interfaces of LPLDH are optimized mainly through hydrophilic interactions rather than hydrophobic interactions, compared with other LDHs. The subunit interfaces of LPLDH are more specifically stabilized by increased numbers of intersubunit salt bridges and hydrogen bonds, and higher geometrical complementarity. Such high specificity at the subunit interfaces should hinder the rearrangement of the quaternary structure needed for allosteric regulation and thus explain the "non-allostery" of LPLDH.
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Arai K, Hishida A, Ishiyama M, Kamata T, Uchikoba H, Fushinobu S, Matsuzawa H, Taguchi H. An absolute requirement of fructose 1,6-bisphosphate for the Lactobacillus casei L-lactate dehydrogenase activity induced by a single amino acid substitution. Protein Eng Des Sel 2002; 15:35-41. [PMID: 11842236 DOI: 10.1093/protein/15.1.35] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Lactobacillus casei allosteric L-lactate dehydrogenase (L-LDH) absolutely requires fructose 1,6-bisphosphate [Fru(1,6)P2] for its catalytic activity under neutral conditions, but exhibits marked catalytic activity in the absence of Fru(1,6)P(2) under acidic conditions through the homotropic activation effect of substrate pyruvate. In this enzyme, a single amino acid replacement, i.e. that of His205 conserved in the Fru(1,6)P(2)-binding site of certain allosteric L-LDHs of lactic acid bacteria with Thr, did not induce a marked loss of the activation effect of Fru(1,6)P(2) or divalent metal ions, which are potent activators that improve the activation function of Fru(1,6)P(2) under neutral conditions. However, this replacement induced a great loss of the Fru(1,6)P(2)-independent activation effect of pyruvate or pyruvate analogs under acidic conditions, consequently indicating an absolute Fru(1,6)P(2) requirement for the enzyme activity. The replacement also induced a significant reduction in the pH-dependent sensitivity of the enzyme to Fru(1,6)P(2), through a slight decrease and increase of the Fru(1,6)P(2) sensitivity under acidic and neutral conditions, respectively, indicating that His205 is also largely involved in the pH-dependent sensitivity of L.casei L-LDH to Fru(1,6)P(2). The role of His205 in the allosteric regulation of the enzyme is discussed on the basis of the known crystal structures of L-LDHs.
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Affiliation(s)
- Kazuhito Arai
- Department of Applied Biological Science, Science University of Tokyo, Japan
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Kimmel JL, Reinhart GD. Isolation of an individual allosteric interaction in tetrameric phosphofructokinase from Bacillus stearothermophilus. Biochemistry 2001; 40:11623-9. [PMID: 11560513 DOI: 10.1021/bi010844a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phosphofructokinase from Bacillus stearothermophilus (BsPFK) is a model allosteric enzyme system in which the interactions between substrates and allosteric effectors have been extensively studied. However, the oligomeric nature of BsPFK has made it difficult to determine the molecular basis of the allosteric regulation because of the multitude of different types of heterotropic and homotropic interactions that are possible between the four active sites and four allosteric sites in the native tetramer. In an attempt to alleviate the complexity of the system and thereby allow the quantitation of a single interaction between one active site and one allosteric site, site-directed mutagenesis has been coupled with a hybrid-forming scheme to create and isolate a tetramer of BsPFK in which only a single active site and a single allosteric site are capable of binding their respective ligands with high (i.e., near wild type) affinity. Characterization of this single allosteric interaction indicates that the free energy involved in the inhibition by the allosteric effector phosphoenolpyruvate (PEP) is 1.48 +/- 0.15 kcal/mol compared to the 3.58 +/- 0.02 kcal/mol measured for the enzyme.
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Affiliation(s)
- J L Kimmel
- Department of Biochemistry and Biophysics and Center for Advanced Biomolecular Research, Texas A&M University, 2128 TAMU, College Station, Texas 77843-2128, USA
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Kelley-Loughnane N, Kantrowitz ER. Binding of AMP to two of the four subunits of pig kidney fructose-1,6-bisphosphatase induces the allosteric transition. Proteins 2001; 44:255-61. [PMID: 11455598 DOI: 10.1002/prot.1090] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
To study the allosteric transition in pig kidney fructose 1,6-bisphosphatase (FBPase), we constructed hybrids in which subunits have either their active or regulatory sites rendered nonfunctional by specific mutations. This was accomplished by the coexpression of the enzyme from a plasmid that contained two slightly different copies of the cDNA. To resolve and purify each of the hybrid enzymes, six aspartic acid codons were added before the termination codon of one of the cDNAs. The addition of these Asp residues to the protein did not alter the kinetic or allosteric properties of the resulting FBPase. Expression of the enzyme from a dual-gene plasmid resulted in the production of a set of five different enzymes (two homotetramers and three hybrid tetramers) that could be purified by a combination of affinity and anion-exchange chromatography because of the differential charge on each of these species. The hybrid with one subunit that only had a functional regulatory site (R) and three subunits that only had a functional active site (A) exhibited biphasic AMP inhibition. Analysis of these data suggest that the binding of AMP to the R subunit is able to globally alter the activity of the other three A subunits. The hybrid composed of two R and two A subunits is completely inhibited at an AMP concentration of approximately 0.5 mM, 100-fold less than the concentration required to fully inhibit the A(4) enzyme. The monophasic nature of this cooperative inhibition suggests that the AMP binding to the two R subunits is sufficient to completely inhibit the enzyme and suggests that the binding of AMP to only two of the four subunits of the enzyme induces the global allosteric transition from the R to the T state.
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Affiliation(s)
- N Kelley-Loughnane
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA
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25
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Nelson SW, Honzatko RB, Fromm HJ. Spontaneous subunit exchange in porcine liver fructose-1,6-bisphosphatase. FEBS Lett 2001; 492:254-8. [PMID: 11257504 DOI: 10.1016/s0014-5793(01)02262-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
No evidence to date suggests the possibility of subunit exchange between tetramers of mammalian fructose-1,6-bisphosphatase. An engineered fructose-1,6-bisphosphatase, with subunits of altered electrostatic charge, exhibits spontaneous subunit exchange with wild-type enzyme in the absence of ligands. The exchange process reaches equilibrium in approximately 5 h at 4 degrees C, as monitored by non-denaturing gel electrophoresis and anion exchange chromatography. Active site ligands, such as fructose 6-phosphate, abolish subunit exchange at the level of the monomer, but permit dimer-dimer exchanges. AMP, alone or in the presence of active site ligands, abolishes all exchange processes. Exchange phenomena may play a role in the kinetic mechanism of allosteric regulation of fructose-1,6-bisphosphatase.
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Affiliation(s)
- S W Nelson
- Department of Biochemistry, Biophysics, and Molecular Biology, 1210 Molecular Biology Bldg., Iowa State University, Ames, IA 50011, USA
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Kondo H, Mori S, Takino H, Kijima H, Yamasaki H, Ozaki M, Tetsuya I, Urata Y, Abe T, Sera Y, Yamakawa K, Kawasaki E, Yamaguchi Y, Kondo T, Eguchi K. Attenuation of expression of gamma-glutamylcysteine synthetase by ribozyme transfection enhance insulin secretion by pancreatic beta cell line, MIN6. Biochem Biophys Res Commun 2000; 278:236-40. [PMID: 11071878 DOI: 10.1006/bbrc.2000.3776] [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] [Indexed: 11/22/2022]
Abstract
Low levels of intracellular antioxidant enzyme activities as well as glutathione (GSH) concentrations have been described in pancreatic beta cells. We examined the effects of intracellular GSH depletion on insulin secretion and the role of intracellular GSH in signal transduction in beta cell line, MIN6 cells. Anti-gamma-glutamylcysteine synthetase (gamma-GCS) heavy subunit ribozyme was stably transfected to MIN6 cells to reduce intracellular GSH concentration. In the presence of 10 mM glucose, ribozyme-transfected cells (RTC) increased insulin secretion from 0.58 microg/10(6) cells/h in control cells (CC) to 1.48 microg/10(6) cells/h. This was associated with increased intracellular Ca(2+) concentration in RTC, detected by fluo-3 staining. Our results demonstrated that intracellular GSH concentration might influence insulin secretion by MIN6 cells, and suggest that enhanced insulin secretion by beta cells conditioned by chronic depletion of GSH is mediated by increased intracellular Ca(2+) concentration.
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Affiliation(s)
- H Kondo
- First Department of Internal Medicine, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan
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27
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Kawata Y, Tamura K, Kawamura M, Ikei K, Mizobata T, Nagai J, Fujita M, Yano S, Tokushige M, Yumoto N. Cloning and over-expression of thermostable Bacillus sp. YM55-1 aspartase and site-directed mutagenesis for probing a catalytic residue. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:1847-57. [PMID: 10712618 DOI: 10.1046/j.1432-1327.2000.01190.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A thermostable aspartase gene (aspB) from Bacillus sp. YM55-1 was cloned and the gene sequenced. The aspB gene (1407 bp ORF) encodes a protein with a molecular mass of 51 627 Da, consisting of 468 amino-acid residues. An amino-acid sequence comparison revealed that Bacillus YM55-1 aspartase shared 71% homology with Bacillus subtilis aspartase and 49% with Escherichia coli and Pseudomonas fluorescens aspartases. The E. coli TK237/pUCASPB strain, which was obtained by transforming E. coli TK237 (aspartase-null strain) with a vector plasmid (pUCASPB) containing the cloned aspB gene, produced a large amount of the enzyme corresponding to > 10% of the total soluble protein. The over-expressed recombinant enzyme (native molecular mass: 200 kDa) was purified effectively and rapidly using heat treatment and affinity chromatography. In order to probe the catalytic residues of this enzyme, two conserved amino-acid residues, Lys183 and His134, were individually mutated to alanine. Although the tertiary structure of each mutant was estimated to be the same as that of wild-type aspartase in CD and fluorescence measurements, the Lys183Ala mutant lost its activity completely, whereas His134Ala retained full activity. This finding suggests that Lys183 may be involved in the catalytic activity of this thermostable Bacillus YM55-1 aspartase.
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Affiliation(s)
- Y Kawata
- Department of Biotechnology, Tottori University, Japan.
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28
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Abstract
Cell membrane redox systems carry electrons from intracellular donors and transport them to extracellular acceptors. This phenomenon appears to be universal. Numerous reviews have emphasized not only the bioenergetic mechanisms of redox systems but also the antioxidant defense mechanisms in which they participate. Moreover, significant progress has been made in the modulation of the membrane redox systems on cell proliferation. Because membrane redox systems play a key role in the regulation of cell growth, they need to be somehow linked into the signaling pathways resulting in either controlled or unregulated growth by both internal and external signals. Ultimately, these sequential events lead to either normal cell proliferation or cancer cell formation. However, much less is known about the involvement of membrane redox in transformation or tumorgenesis. In this review, the facts and ideas are summarized concerning the redox systems and tumorgenesis in several aspects, such as the regulation of cell growth and the effect on cell differentiation and on signaling pathways. In addition, information on a unique tumor-associated nicotinamide adenine dinucleotide (NADH) oxidase (tNOX) protein is reviewed.
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Affiliation(s)
- P J Chueh
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA.
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Ni L, Zhou J, Hurley TD, Weiner H. Human liver mitochondrial aldehyde dehydrogenase: three-dimensional structure and the restoration of solubility and activity of chimeric forms. Protein Sci 1999; 8:2784-90. [PMID: 10631996 PMCID: PMC2144226 DOI: 10.1110/ps.8.12.2784] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Human liver cytosolic and mitochondrial isozymes of aldehyde dehydrogenase share 70% sequence identity. However, the first 21 residues are not conserved between the human isozymes (15% identity). The three-dimensional structures of the beef mitochondrial and sheep cytosolic forms have virtually identical three-dimensional structures. Here, we solved the structure of the human mitochondrial enzyme and found it to be identical to the beef enzyme. The first 21 residues are found on the surface of the enzyme and make no contact with other subunits in the tetramer. A pair of chimeric enzymes between the human isozymes was made. Each chimera had the first 21 residues from one isozyme and the remaining 479 from the other. When the first 21 residues were from the mitochondrial isozyme, an enzyme with cytosolic-like properties was produced. The other was expressed but was insoluble. It was possible to restore solubility and activity to the chimera that had the first 21 cytosolic residues fused to the mitochondrial ones by making point mutations to residues at the N-terminal end. When residue 19 was changed from tyrosine to a cysteine, the residue found in the mitochondrial form, an active enzyme could be made though the Km for NAD+ was 35 times higher than the native mitochondrial isozyme and the specific activity was reduced by 75%. This residue interacts with residue 203, a nonconserved, nonactive site residue. A mutation of residue 18, which also interacts with 203, restored solubility, but not activity. Mutation to residue 15, which interacts with 104, also restored solubility but not activity. It appears that to have a soluble or active enzyme a favorable interaction must occur between a residue in a surface loop and a residue elsewhere in the molecule even though neither make contact with the active site region of the enzyme.
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Affiliation(s)
- L Ni
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153, USA
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30
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Chinni SR, Brenz M, Shisheva A. Modulation of GDP-dissociation inhibitor protein membrane retention by the cellular redox state in adipocytes. Exp Cell Res 1998; 242:373-80. [PMID: 9665834 DOI: 10.1006/excr.1998.4105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Small GTPases of the Rab family play a key role in the regulation of vesicular transport in eukaryotic cells. As they cycle on and off membranes, Rab proteins rely on the escort services of the GDP-dissociation inhibitor (GDI) proteins. While specific recognition of Rab-GDI complexes by membrane targets is suggested, the mechanisms underlying the subsequent GDI release into the cytosol remain unknown. In this study, we demonstrate that modulations of the cellular redox status in intact rat fat cells, 3T3-L1 adipocytes in culture, and other cultured cell types result in rapid, effective, dose-dependent, and selective membrane dynamics of GDI-1 and -2, membrane retention under reduced redox state, or dissociation under oxidized conditions. GDI retention on adipocyte membranes is associated with a complete arrest of insulin-induced translocation of GLUT4 glucose transporters onto plasma membrane. Together, these data suggest, first, that following Rab delivery to membranes, GDI release is promoted by a shift in the redox state and, second, that arrest of GDIs on membranes inhibits intracellular membrane trafficking events.
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Affiliation(s)
- S R Chinni
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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31
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Fushinobu S, Ohta T, Matsuzawa H. Homotropic activation via the subunit interaction and allosteric symmetry revealed on analysis of hybrid enzymes of L-lactate dehydrogenase. J Biol Chem 1998; 273:2971-6. [PMID: 9446610 DOI: 10.1074/jbc.273.5.2971] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
L-Lactate dehydrogenase from Bifidobacterium longum shows homotropic activation by pyruvate as well as heterotropic activation by fructose 1,6-bisphosphate. Hybrid enzymes were produced from the wild-type subunit and a mutant subunit, whose substrate specificity was altered to that of malate dehydrogenase, and separated to analyze the substrate-induced homotropic activation mechanism. Oxamate, a competitive inhibitor of L-lactate dehydrogenase, was used to mimic the substrate-induced activation of the wild-type subunit as "a regulatory subunit." The malate dehydrogenase activity of the mutant subunit as "the catalytic subunit" of the hybrid enzymes was measured, and the activity of the mutant subunit was activated on the addition of oxamate. Thus, we directly observed the inter-subunit homotropic activation transmitted from the wild-type to the mutant subunit. Moreover, "isomeric" hybrid enzymes that have different structural subunit arrangements but identical subunit compositions showed identical kinetic natures. This indicates that the enzyme maintains its subunit symmetry during the allosteric transition.
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Affiliation(s)
- S Fushinobu
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113, Japan
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