101
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Isupov MN, Antson AA, Dodson EJ, Dodson GG, Dementieva IS, Zakomirdina LN, Wilson KS, Dauter Z, Lebedev AA, Harutyunyan EH. Crystal structure of tryptophanase. J Mol Biol 1998; 276:603-23. [PMID: 9551100 DOI: 10.1006/jmbi.1997.1561] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The X-ray structure of tryptophanase (Tnase) reveals the interactions responsible for binding of the pyridoxal 5'-phosphate (PLP) and atomic details of the K+ binding site essential for catalysis. The structure of holo Tnase from Proteus vulgaris (space group P2(1)2(1)2(1) with a = 115.0 A, b = 118.2 A, c = 153.7 A) has been determined at 2.1 A resolution by molecular replacement using tyrosine phenol-lyase (TPL) coordinates. The final model of Tnase, refined to an R-factor of 18.7%, (Rfree = 22.8%) suggests that the PLP-enzyme from observed in the structure is a ketoenamine. PLP is bound in a cleft formed by both the small and large domains of one subunit and the large domain of the adjacent subunit in the so-called "catalytic" dimer. The K+ cations are located on the interface of the subunits in the dimer. The structure of the catalytic dimer and mode of PLP binding in Tnase resemble those found in aspartate amino-transferase, TPL, omega-amino acid pyruvate aminotransferase, dialkylglycine decarboxylase (DGD), cystathionine beta-lyase and ornithine decarboxylase. No structural similarity has been detected between Tnase and the beta 2 dimer of tryptophan synthase which catalyses the same beta-replacement reaction. The single monovalent cation binding site of Tnase is similar to that of TPL, but differs from either of those in DGD.
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Affiliation(s)
- M N Isupov
- Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russia
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102
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Zhu Z, Davidson VL. Kinetic and chemical mechanisms for the effects of univalent cations on the spectral properties of aromatic amine dehydrogenase. Biochem J 1998; 329 ( Pt 1):175-82. [PMID: 9405291 PMCID: PMC1219029 DOI: 10.1042/bj3290175] [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: 02/05/2023]
Abstract
Univalent cations and pH influence the UV-visible absorption spectrum of the tryptophan tryptophylquinone (TTQ) enzyme, aromatic amine dehydrogenase (AADH). Little spectral perturbation was observed when pH was varied in the absence of univalent cations. The addition of alkali metal univalent cations (K+, Na+, Li+, Rb+ or Cs+) to oxidized AADH caused significant changes in its absorption spectrum. The apparent Kd for each cation, determined from titrations of the spectral perturbation, decreased with increasing pH. Transient kinetic studies involving rapid mixing of AADH with cations and pH jump revealed that the rate of the cation-induced spectral changes initially decreased with increasing cation concentration to a minimum value, then increased with increasing cation concentration. A kinetic model was developed to fit these data, determine the true pH-independent Kd values for K+ and Na+, and explain the pH-dependence of the apparent Kd. A chemical reaction mechanism, based on the kinetic data, is presented in which the metallic univalent cation facilitates the chemical modification of the TTQ prosthetic group to form an hydroxide adduct which gives rise to the spectral change. Addition of NH4(+)/NH3 to AADH caused changes in the absorption spectrum which were very different form those caused by addition of the metallic univalent cations. The kinetics of the reaction induced by addition of NH4+/NH3 were also different, being simple saturation kinetics. Another reaction mechanism is proposed for the NH4+/NH3-induced spectral change that involves nucleophilic addition of the unprotonated NH3 to TTQ. The general relevance of these data and models to the physiological reactions of TTQ-dependent enzymes and to the roles of univalent cations in modulating enzyme activity are discussed.
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Affiliation(s)
- Z Zhu
- Department of Biochemistry, University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
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103
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Xiang B, Markham GD. Probing the mechanism of inosine monophosphate dehydrogenase with kinetic isotope effects and NMR determination of the hydride transfer stereospecificity. Arch Biochem Biophys 1997; 348:378-82. [PMID: 9434751 DOI: 10.1006/abbi.1997.0439] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mechanism of human type II inosine monophosphate dehydrogenase has been probed by measurements of primary deuterium kinetic isotope effects, and by determination of the stereochemical course of the reaction. The deuterium isotope effects on Vmax from [2-deutero]-IMP are unity for reactions with a variety of monovalent cation activators (K+, NH4+, Na+, Rb+) of various efficacy. In each case normal effects on Vmax/K(m) in the range of 1.9 to 3.5 are observed for both IMP and NAD, and are larger for NAD. These results demonstrate that both substrates can dissociate from the E.M+.IMP.NAD complex, therefore the kinetic mechanism is not ordered as previous steady-state kinetic studies have suggested. Comparison of reaction rates in D2O and H2O show no 2H isotope effect on Vmax, and a < or = twofold decrease in Vmax/K(m); thus, a proton transfer from solvent is not rate-limiting in turnover. The NMR spectrum of the [4-deutero]NADH produced in the reaction of [2-deutero]-IMP and NAD shows that the hydrogen is transferred to the B, or pro-S, side of the nicotinamide ring. Presteady-state kinetic experiments reveal a burst of NADH formation in the first turnover, demonstrating that a late step in the mechanism is rate-limiting. The rate of the burst phase is reduced approximately twofold with [2-deutero]IMP as substrate, indicating that the hydride transfer step is kinetically significant early in the reaction.
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Affiliation(s)
- B Xiang
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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104
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Trchounian A. Ion Exchange in Facultative Anaerobes: Does a Proton-potassium Pump Exist in AnaerobicEscherichia Coli? Anaerobe 1997; 3:355-71. [PMID: 16887611 DOI: 10.1006/anae.1997.0122] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/1997] [Accepted: 05/27/1997] [Indexed: 11/22/2022]
Affiliation(s)
- A Trchounian
- Department of Biophysics, Biological Faculty of Yerevan State University, 375049, Yerevan, Armenia.
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105
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Ramírez-Silva L, Oria J, Gómez-Puyou A, Tuena de Gómez-Puyou M. The contribution of water to the selectivity of pyruvate kinase for Na+ and K+. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 250:583-9. [PMID: 9428713 DOI: 10.1111/j.1432-1033.1997.0583a.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
For many years it has been known that K+ is an essential activator of pyruvate kinase [Kachmar, J. F. & Boyer, P. D. (1953) J. Biol. Chem. 200, 669-683] and that Na+ induces relatively small enhancements of activity. The effect of these two alkali metal ions on the activity of pyruvate kinase entrapped in the low water environment of reverse 'micelles formed with cetyltrimethylammonium, hexanol, n-octane and various water concentrations was studied. In reverse micelles with 3.6% water, the activity with 7 mM Na+ is more than 82 times higher than in aqueous solution with an equivalent Na+ concentration. As the concentration of water in reverse micelles is raised, the activating effect of relatively low concentrations of Na+ (or K+) decreases simultaneously to a more than 100-fold increase in the concentration of Na+ or K+ required for attaining half-maximal activation. Similar results were obtained with NH4+, Rb+ and Cs+. Therefore, the amount of water in the system is critical for observing activation by alkali metal ions. In fact, the concentration of Na+ required for half-maximal activation in standard aqueous media is higher than the concentrations that can be experimentally assayed. As evidenced from fluorescence and kinetic data, it appears that the entrapment of pyruvate kinase in reverse micelles does not produce gross structural alterations. Therefore, it is suggested that in conventional aqueous systems, the basis of the high discrimination between Na+ and K+ by pyruvate kinase is the higher energy required for desolvating Na+. Nevertheless, at all the water concentrations studied, the activities reached with K+ were higher than with Na+ which suggests that the Na+ form of the enzyme has a lower catalytic capacity than the K+-enzyme complex.
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Affiliation(s)
- L Ramírez-Silva
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México., México, DF
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106
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Bohlmann J, Steele CL, Croteau R. Monoterpene synthases from grand fir (Abies grandis). cDNA isolation, characterization, and functional expression of myrcene synthase, (-)-(4S)-limonene synthase, and (-)-(1S,5S)-pinene synthase. J Biol Chem 1997; 272:21784-92. [PMID: 9268308 DOI: 10.1074/jbc.272.35.21784] [Citation(s) in RCA: 188] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Grand fir (Abies grandis) has been developed as a model system for studying defensive oleoresin formation in conifers in response to insect attack or other injury. The turpentine fraction of the oleoresin is a complex mixture of monoterpene (C10) olefins in which (-)-limonene and (-)-alpha- and (-)-beta-pinene are prominent components; (-)-limonene and (-)-pinene synthase activities are also induced upon stem wounding. A similarity based cloning strategy yielded three new cDNA species from a wounded stem cDNA library that appeared to encode three distinct monoterpene synthases. After expression in Escherichia coli and enzyme assay with geranyl diphosphate as substrate, subsequent analysis of the terpene products by chiral phase gas chromatography and mass spectrometry showed that these sequences encoded a (-)-limonene synthase, a myrcene synthase, and a (-)-pinene synthase that produces both alpha-pinene and beta-pinene. In properties and reaction stereochemistry, the recombinant enzymes resemble the corresponding native monoterpene synthases of wound-induced grand fir stem. The deduced amino acid sequences indicated the limonene synthase to be 637 residues in length (73.5 kDa), the myrcene synthase to be 627 residues in length (72.5 kDa), and the pinene synthase to be 628 residues in length (71.5 kDa); all of these monoterpene synthases appear to be translated as preproteins bearing an amino-terminal plastid targeting sequence. Sequence comparison revealed that these monoterpene synthases from grand fir resemble sesquiterpene (C15) synthases and diterpene (C20) synthases from conifers more closely than other monoterpene synthases from angiosperm species. This similarity between extant monoterpene, sesquiterpene, and diterpene synthases of gymnosperms is surprising since functional diversification of this enzyme class is assumed to have occurred over 300 million years ago. Wound-induced accumulation of transcripts for monoterpene synthases was demonstrated by RNA blot hybridization using probes derived from the three monoterpene synthase cDNAs. The availability of cDNA species encoding these monoterpene synthases will allow an understanding of the regulation of oleoresin formation in conifers and will ultimately permit the transgenic manipulation of this defensive secretion to enhance resistance to insects. These cDNAs also furnish tools for defining structure-function relationships in this group of catalysts that generate acyclic, monocyclic, and bicyclic olefin products.
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Affiliation(s)
- J Bohlmann
- Institute of Biological Chemistry, and Department of Biochemistry and Biophysics, Washington State University, Pullman, Washington 99164-6340, USA
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107
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Huang H, Goldberg AL. Proteolytic activity of the ATP-dependent protease HslVU can be uncoupled from ATP hydrolysis. J Biol Chem 1997; 272:21364-72. [PMID: 9261150 DOI: 10.1074/jbc.272.34.21364] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
HslVU is a new Escherichia coli ATP-dependent protease composed of two multimeric complexes: the HslU ATPase and the HslV peptidase. Prior studies indicated that HslVU requires ATP hydrolysis for the cleavage of peptides and proteins. We show here that ATP concentrations that activate hydrolysis of benzyloxycarbonyl-Gly-Gly-Leu-7-amido-4-methylcoumarin are 50-100 fold lower than those necessary for degradation of proteins (e.g. casein). Also, the nonhydrolyzable analogs of ATP, 5'-adenylyl beta, gamma-imidodiphosphate (AMP-PNP) and adenosine 5'-(alpha, beta-methylene)triphosphate, can support peptide hydrolysis, but only after an initial time lag not seen with ATP. This delay decreased at higher temperatures and with higher HslU or HslV concentrations and was eliminated by preincubation of HslU and HslV together. Thus, ATP hydrolysis accelerates the association of HslU and HslV, which occurs slowly with the nonhydrolyzable analog. The addition of KCl stimulated 4-6-fold the peptidase activity with AMP-PNP present and eliminated the time lag, but KCl had no stimulatory effect with ATP. NH4+ and Cs+ had similar effects as K+, but Na+ and Li+ were ineffective. AMP-PNP by itself supported hydrolysis of casein and other polypeptides only 20% as well as ATP, but in the presence of K+, Cs+, or NH4+, AMP-PNP activated casein degradation even better than ATP, although it was not hydrolyzed. In addition, MgCl2, MnCl2, and CaCl2 allowed some peptidase and caseinase activity in the absence of any nucleotide. However, Mn2+ and Ca2+, unlike Mg2+, abolished ATP hydrolysis and prevented further activation by ATP or AMP-PNP. These findings indicate that ATP binding to a high affinity site triggers the formation of an active state capable of peptide cleavage, although ATP hydrolysis facilitates this process. Rapid degradation of proteins requires a distinct state of the enzyme, which is normally reached through ATP hydrolysis at low affinity sites. However, AMP-PNP binding together with K+ can induce a form of HslVU that degrades proteins without energy consumption.
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Affiliation(s)
- H Huang
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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108
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Abstract
When Na+ binds to thrombin, a conformational change is induced that renders the enzyme kinetically faster and more specific in the activation of fibrinogen. Two Na+ binding sites have here been identified crystallographically by exchanging Na+ with Rb+. One is intermolecular, found on the surface between two symmetry-related thrombin molecules. Since it is not present in thrombin crystal structures having different crystal systems, the other Na+ site is the functionally relevant one. The second site has octahedral coordination with the carbonyl oxygen atoms of Arg221A and Lys224 and four conserved water molecules. It is located near Asp189 of the S1 specificity site in an elongated solvent channel (8 x 18 A) formed by four antiparallel beta-strands between Cys182-Cys191 and Val213-Tyr228. This channel, extending from the active site to the opposite surface of the enzyme, was first noted in the hirudin-thrombin structure and contains about 20 conserved water molecules linked together by a hydrogen bonding network that connects to the main chain of thrombin. Although the antiparallel beta-strand interactions of the functional Na+ binding site are the same in prethrombin2, the loops between the strands are very different, so that Asp189 and Arg221A are not positioned properly for either substrate or Na+ binding in prethrombin2. A water molecule with octahedral coordination has also been identified in factor Xa at the topologically equivalent Na+ site position of thrombin. Since activated protein C shows enhanced activity with monovalant cation binding, the same position is probably utilized by Na+. Since thrombin crystals could not be grown in the absence of Na+, the cation was leached from Na(+)-bound thrombin crystals by diffusion/exchange. Although both Na+ and their coordinating water molecules were removed from the Na+ binding sites, the remainder of the thrombin structure was, unexpectedly, the same. The lack of an allosteric change is most likely attributable to crystal packing effects. Thus, the structure of the slow form remains to be established crystallographically.
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Affiliation(s)
- E Zhang
- Department of Chemistry, Michigan State University, East Lansing 48824, USA
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109
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Dang QD, Di Cera E. Residue 225 determines the Na(+)-induced allosteric regulation of catalytic activity in serine proteases. Proc Natl Acad Sci U S A 1996; 93:10653-6. [PMID: 8855234 PMCID: PMC38209 DOI: 10.1073/pnas.93.20.10653] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Residue 225 in serine proteases is typically Pro or Tyr and specifies an important and unanticipated functional aspect of this class of enzymes. Proteases with Y225, like thrombin, are involved in highly specialized functions like blood coagulation and complement that are exclusively found in vertebrates. In these proteases, the catalytic activity is enhanced allosterically by Na+ binding. Proteases with P225, like trypsin, are typically involved in digestive functions and are also found in organisms as primitive as eubacteria. These proteases have no requirement for Na+ or other monovalent cations. The molecular origin of this physiologically important difference is remarkably simple and is revealed by a comparison of the Na+ binding loop of thrombin with the homologous region of trypsin. The carbonyl O atom of residue 224 makes a key contribution to the coordination shell of the bound Na+ in thrombin, but is oriented in a manner incompatible with Na+ binding in trypsin because of constraints imposed by P225 on the protein backbone. Pro at position 225 is therefore incompatible with Na+ binding and is a direct predictor of the lack of allosteric regulation in serine proteases. To directly test this hypothesis, we have engineered the thrombin mutant Y225P. This mutant has lost the ability to bind Na+ and behaves like the allosteric slow (Na(+)-free) form. The Na(+)-induced allosteric regulation also bears on the molecular evolution of serine proteases. A strong correlation exists between residue 225 and the codon used for the active site S195. Proteases with P225 typically use a TCN codon for S195, whereas proteases with Y225 use an AGY codon. It is proposed that serine proteases evolved from two main lineages: (i) TCN/P225 with a trypsin-like ancestor and (ii) AGY/Y225 with a thrombin-like ancestor. We predict that the Na(+)-induced allosteric regulation of catalytic activity can be introduced in the TCN/P225 lineage using the P225Y replacement.
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Affiliation(s)
- Q D Dang
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
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110
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111
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Perkins J, Gadd GM. Interactions of Cs+ and other monovalent cations (Li+, Na+, K+, Rb+, NH4+) with K+-dependent pyruvate kinase and malate dehydrogenase from the yeasts Rhodotorula rubra and Saccharomyces cerevisiae. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s0953-7562(96)80142-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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112
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Glasemacher J, Siebers A, Altendorf K, Schönheit P. Low-affinity potassium uptake system in the archaeon Methanobacterium thermoautotrophicum: overproduction of a 31-kilodalton membrane protein during growth on low-potassium medium. J Bacteriol 1996; 178:728-34. [PMID: 8550507 PMCID: PMC177719 DOI: 10.1128/jb.178.3.728-734.1996] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
During growth on low-K+ medium (1 mM K+), Methanobacterium thermoautotrophicum accumulated K+ up to concentration gradients ([K+]intracellular/[K+]extracellular) of 25,000- to 50,000-fold. At these gradients ([K+]extracellular of < 20 microM), growth ceased but could be reinitiated by the addition of K+ or Rb+. During K+ starvation, the levels of a protein with an apparent molecular weight of 31,000 increased about sixfold. The protein was associated with the membrane and could be extracted by detergents. Cell suspensions of M. thermoautotrophicum obtained after K+-limited growth catalyzed the transport of both K+ and Rb+ with apparent Km and Vmax values of 0.13 mM and 140 nmol/min/mg, respectively, for K+ and 3.4 mM and 140 nmol/min/mg, respectively, for Rb+. Rb+ competitively inhibited K+ uptake with an inhibitor constant of about 10 mM. Membranes of K+-starved cells did not exhibit K+-stimulated ATPase activity. Immunoblotting with antisera against Escherichia coli Kdp-ATPase did not reveal any specific cross-reactivity against membrane proteins of K+-starved cells. Cells of M. thermoautotrophicum grown at a high potassium concentration (50 mM) catalyzed K+ and Rb+ transport at similar apparent Km values (0.13 mM for K+ and 3.3 mM for Rb+) but at significantly lower apparent Vmax values (about 60 nmol/min/mg for both K+ and Rb+) compared with K+-starved cells. From these data, it is concluded that the archaeon M. thermoautotrophicum contains a low-affinity K+ uptake system which is overproduced during growth on low-K+ medium.
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Affiliation(s)
- J Glasemacher
- Institut für Pfanzenphysiologie und Mikrobiologie, Freie Universität Berlin, Germany
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113
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Abstract
The classical Botts-Morales theory for the action of a modifier on the catalytic properties of an enzyme has been extended to deal with allosteric effects in serine proteases. The exact analytical solution derived for the linkage scheme at steady state provides a rigorous framework for the study of many biologically relevant systems, including enzymes activated by monovalent cations and cofactor-controlled protease-zymogen interactions in blood coagulation. When the enzyme obeys Michaelis-Menten kinetics, the exact solution of the kinetic linkage scheme simplifies considerably. Of particular importance for practical applications is a simple equation expressing the dependence of the specificity constant of the enzyme, kcat/Km, on the concentration of the modifier, from which the equilibrium binding constant for the formation of the enzyme-modifier complex can be estimated. Analysis of the allosteric changes in thrombin activity induced by thrombomodulin and Na+ in terms of this equation yields accurate determinations of the equilibrium binding constants for both effectors.
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Affiliation(s)
- E Di Cera
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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114
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115
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Di Cera E, Guinto ER, Vindigni A, Dang QD, Ayala YM, Wuyi M, Tulinsky A. The Na+ binding site of thrombin. J Biol Chem 1995; 270:22089-92. [PMID: 7673182 DOI: 10.1074/jbc.270.38.22089] [Citation(s) in RCA: 203] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Thrombin is an allosteric serine protease existing in two forms, slow and fast, targeted toward anticoagulant and procoagulant activities. The slow --> fast transition is induced by Na+ binding to a site contained within a cylindrical cavity formed by three antiparallel beta-strands of the B-chain (Met180-Tyr184a, Lys224-Tyr228, and Val213-Gly219) diagonally crossed by the Glu188-Glu192 strand. The site is shaped further by the loop connecting the last two beta-strands and is located more than 15 A away from the catalytic triad. The cavity traverses through thrombin from the active site to the opposite surface and contains Asp189 of the primary specificity site near its midpoint. The bound Na+ is coordinated octahedrally by the carbonyl oxygen atoms of Tyr184a, Arg221a, and Lys224, and by three highly conserved water molecules in the D-Phe-Pro-Arg chloromethylketone thrombin. The sequence in the Na+ binding loop is highly conserved in thrombin from 11 different species and is homologous to that found in other serine proteases involved in blood coagulation. Mutation of two Asp residues flanking Arg221a (D221A/D222K) almost abolishes the allosteric properties of thrombin and shows that the Na+ binding loop is also involved in direct recognition of protein C and antithrombin.
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Affiliation(s)
- E Di Cera
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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116
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McQueney MS, Markham GD. Investigation of monovalent cation activation of S-adenosylmethionine synthetase using mutagenesis and uranyl inhibition. J Biol Chem 1995; 270:18277-84. [PMID: 7629147 DOI: 10.1074/jbc.270.31.18277] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
S-Adenosylmethionine (AdoMet) synthetase catalyzes the formation of AdoMet from ATP and L-methionine with subsequent hydrolysis of the bound tripolyphosphate intermediate. Maximal activity requires the presence of two divalent and one monovalent cation per active site. Recently, the x-ray structure of the Escherichia coli AdoMet synthetase was solved, and the positions of the two Mg2+ binding sites were identified. Based on additional spherical electron density, the K+ binding site was postulated to be a nearby site where the uranyl heavy atom derivative also bound in the crystal. The side chain of glutamate 42 is within ligation distance of the metals. Mutagenesis of glutamate 42 to glutamine (E42QMetK) abolished monovalent cation activation and produced an enzyme that has kinetic properties virtually identical to those of K(+)-free wild type AdoMet synthetase in both the overall AdoMet synthetase reaction and in the hydrolysis of tripolyphosphate. Thus, there is a approximately 100-fold decrease in the Vmax for AdoMet synthesis and large increases in the Km values for both substrates. In contrast there is only a 2-fold decrease in Vmax for tripolyphosphate hydrolysis. The uranyl ion, UO2(2+), is a competitive inhibitor with respect to K+ (Ki = 350 nM) and is the first ion to bind at this site and inhibit the enzyme. The UO2(2+) inhibition is reversible and tight-binding, and results from UO2(2+) and not UO2(2+)-ATP. Analogous to K+ activation, UO2(2+) predominantly inhibits AdoMet formation rather than tripolyphosphate hydrolysis. The kinetic results indicate that UO2(2+) inhibition is likely to result from interference with productive ATP binding. UO2(2+) remains a tight-binding inhibitor of the E42Q mutant, which suggests that K+ and UO2(2+) have different ligation preferences when bound in the monovalent cation binding pocket. The results support the model that glutamate 42 provides ligands to the K+ and has a major role in monovalent cation binding.
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Affiliation(s)
- M S McQueney
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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117
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Woehl EU, Dunn MF. Monovalent metal ions play an essential role in catalysis and intersubunit communication in the tryptophan synthase bienzyme complex. Biochemistry 1995; 34:9466-76. [PMID: 7626617 DOI: 10.1021/bi00029a023] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This investigation shows that the alpha 2 beta 2 tryptophan synthase bienzyme complex from Salmonella typhimurium is subject to monovalent metal ion activation. The effects of the monovalent metal ions Na+ and K+ were investigated using rapid scanning stopped-flow (RSSF), single-wavelength stopped-flow (SWSF), and steady-state techniques. RSSF measurements of individual steps in the reaction of L-serine and indole to give L-trytophan (the beta-reaction) as well as the reaction of 3-indole-D-glycerol 3'-phosphate (IGP) with L-serine (the alpha beta-reaction) demonstrate that monovalent metal ions such as Na+ and K+ change the distribution of intermediates in both the transient and steady states. Therefore the metal ion effect alters relative ground-state energies and the relative positions of ground- and transition-state energies. The RSSF spectra and SWSF time courses show that the turnover of indole is significantly reduced in the absence of either Na+ or K+. The alpha-aminoacrylate Schiff base species, E(A-A), is in a less active state in the absence of monovalent metal ions. Na+ decreases the steady-state rate of IGP cleavage (the alpha-reaction) to about 30% of the value obtained in the absence of metal ions. Steady-state investigations show that in the absence of monovalent metal ions the alpha- and alpha beta-reactions have the same activity. Na+ binding gives a 30-fold stimulation of the alpha-reaction when the beta-site is in the E(A-A) form.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- E U Woehl
- Department of Biochemistry, University of California at Riverside 92521-0129, USA
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118
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Peracchi A, Mozzarelli A, Rossi GL. Monovalent cations affect dynamic and functional properties of the tryptophan synthase alpha 2 beta 2 complex. Biochemistry 1995; 34:9459-65. [PMID: 7626616 DOI: 10.1021/bi00029a022] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Monovalent cations affect both conformational and catalytic properties of the tryptophan synthase alpha 2 beta 2 complex from Salmonella typhimurium. Their influence on the dynamic properties of the enzyme was probed by monitoring the phosphorescence decay of the unique Trp-177 beta, a residue located near the beta-active site, at the interface between alpha- and beta-subunits. In the presence of either Li+, Na+, Cs+, or NH4+, the phosphorescence decay is biphasic and the average lifetime increases indicating a decrease in the flexibility of the N-terminal domain of the beta-subunit. Since amplitudes but not lifetimes are affected, cations appear to shift the equilibrium between preexisting enzyme conformations. The effect on the reaction between indole and L-serine was studied by steady state kinetic methods at room temperature. We found that cations: (i) bind to the L-serine--enzyme derivatives with an apparent dissociation constant, measured as the concentration of cation corresponding to one-half of the maximal activity, that is in the millimolar range and decreases with ion size; (ii) increase kcat with the order of efficacy Cs+ > K+ > Li+ > Na+; (iii) decrease KM for indole, Na+ being the most effective and causing a 30-fold decrease; and (iv) cause an increase of the kcat/KM ratio by 20-40-fold. The influence on the equilibrium distribution between the external aldimine and the alpha-aminoacrylate, intermediates in the reaction of L-serine with the beta-subunits of the enzyme, was found to be cation-specific.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Peracchi
- Istituto di Scienze Biochimiche, Università di Parma, Italy
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119
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Perkins J, Gadd GM. The influence of pH and external K+ concentration on caesium toxicity and accumulation in Escherichia coli and Bacillus subtilis. JOURNAL OF INDUSTRIAL MICROBIOLOGY 1995; 14:218-25. [PMID: 7598839 DOI: 10.1007/bf01569931] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Toxicity screening of Escherichia coli NCIB 9484 and Bacillus subtilis 007, NCIB 168 and NCIB 1650 has shown Cs+ to be the most toxic Group 1 metal cation. However, toxicity and accumulation of Cs+ by the bacteria was affected by two main external factors; pH and the presence of other monovalent cations, particularly K+. Over the pH range 6-9 both E. coli and B. subtilis showed increasing sensitivity towards caesium as the pH was raised. The presence of K+ and Na+ in the laboratory media used lowered caesium toxicity and lowered accumulation of the metal. In order to assess accurately Cs+ toxicity towards the bacterial strains it was therefore necessary to define the K+:Cs+ ratio in the external medium. The minimum inhibitory K+:Cs+ concentration ratio for the Bacillus strains tested was in the range 1:2-1:3 while E. coli had a minimum inhibitory K+:Cs+ concentration ratio of 1:6.
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Affiliation(s)
- J Perkins
- Department of Biological Sciences, University of Dundee, UK
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120
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Wilbanks SM, McKay DB. How potassium affects the activity of the molecular chaperone Hsc70. II. Potassium binds specifically in the ATPase active site. J Biol Chem 1995; 270:2251-7. [PMID: 7836458 DOI: 10.1074/jbc.270.5.2251] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Crystallographic anomalous scattering from potassium at 1.7 A resolution reveals two monovalent ions that interact with MgADP and P(i) in the nucleotide binding cleft of wild-type recombinant bovine Hsc70 ATPase fragment. K+ at site 1 interacts with oxygens of the beta-phosphate of ADP, whereas K+ at site 2 interacts with an oxygen of P(i). Both K+ ions also interact with specific H2O molecules in the first hydration shell of the octahedrally coordinated Mg2+ ion and with specific protein ligands. In crystals that have Na+ present, K+ is replaced by a Na+ ion at site 1 and by a Na(+)-H2O pair at site 2. The K+ ions are positioned where they could stabilize binding of a beta,gamma-bidentate MgATP complex with Hsc70, as well as a transition state during ATP hydrolysis, suggesting that monovalent ions act as specific metal cofactors in the ATPase reaction of Hsc70.
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Affiliation(s)
- S M Wilbanks
- Beckman Laboratories for Structural Biology, Stanford University School of Medicine, California 94305
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121
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O'Brien MC, McKay DB. How potassium affects the activity of the molecular chaperone Hsc70. I. Potassium is required for optimal ATPase activity. J Biol Chem 1995; 270:2247-50. [PMID: 7836457 DOI: 10.1074/jbc.270.5.2247] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Several functions of the 70-kilodalton heat shock cognate protein (Hsc70), such as peptide binding/release and clathrin uncoating, have been shown to require potassium ions. We have examined the effect of monovalent ions on the ATPase activity of Hsc70. The steady-state ATPase activities of Hsc70 and its amino-terminal 44-kDa ATPase fragment are minimal in the absence of K+ and reach a maximum at approximately 0.1 M [K+]. Activation of the ATPase turnover correlates with the ionic radii of monovalent ions; those that are at least 0.3 A smaller (Na+ and Li+) or larger (Cs+) than K+ show negligible activation, whereas ions with radii differing only approximately 0.1 A from that of K+ (NH4+ and Rb+) activate to approximately half the turnover rate observed with K+. Single turnover experiments with Hsc70 demonstrate that ATP hydrolysis is 5-fold slower with Na+ than with K+. The equilibrium binding of ADP or ATP to Hsc70 is unperturbed when K+ is replaced with Na+. These results are consistent with a role for monovalent ions as specific cofactors in the enzymatic hydrolysis of ATP.
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Affiliation(s)
- M C O'Brien
- Beckman Laboratories for Structural Biology, Stanford University School of Medicine, California 94305
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122
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Avery SV. Caesium accumulation by microorganisms: uptake mechanisms, cation competition, compartmentalization and toxicity. JOURNAL OF INDUSTRIAL MICROBIOLOGY 1995; 14:76-84. [PMID: 7766213 DOI: 10.1007/bf01569888] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The continued release of caesium radioisotopes into the environment has led to a resurgence of interest in microbe-Cs interactions. Caesium exists almost exclusively as the monovalent cation Cs+ in the natural environment. Although Cs+ is a weak Lewis acid that exhibits a low tendency to form complexes with ligands, its chemical similarity to the biologically essential alkali cation K+ facilitates high levels of metabolism-dependent intracellular accumulation. Microbial Cs+ (K+) uptake is generally mediated by monovalent cation transport systems located on the plasma membrane. These differ widely in specificity for alkali cations and consequently microorganisms display large differences in their ability to accumulate Cs+; Cs+ appears to have an equal or greater affinity than K+ for transport in certain microorganisms. Microbial Cs+ accumulation is markedly influenced by the presence of external cations, e.g. K+, Na+, NH4+ and H+, and is generally accompanied by an approximate stoichiometric exchange for intracellular K+. However, stimulation of growth of K(+)-starved microbial cultures by Cs+ is limited and it has been proposed that it is not the presence of Cs+ in cells that is growth inhibitory but rather the resulting loss of K+. Increased microbial tolerance to Cs+ may result from sequestration of Cs+ in vacuoles or changes in the activity and/or specificity of transport systems mediating Cs+ uptake. The precise intracellular target(s) for Cs(+)-induced toxicity has yet to be clearly defined, although certain internal structures, e.g. ribosomes, become unstable in the presence of Cs+ and Cs+ is known to substitute poorly for K+ in the activation of many K(+)-requiring enzymes.
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Affiliation(s)
- S V Avery
- School of Pure and Applied Biology, University of Wales College of Cardiff, UK
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123
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Black C, Huang HW, Cowan J. Biological coordination chemistry of magnesium, sodium, and potassium ions. Protein and nucleotide binding sites. Coord Chem Rev 1994. [DOI: 10.1016/0010-8545(94)80068-5] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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124
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Ertel EA. Modulation of guanylate cyclase and phosphodiesterase by monovalent cations and nucleoside triphosphates in light-sensitive excised patches of rod outer segments. Pflugers Arch 1994; 428:372-81. [PMID: 7529403 DOI: 10.1007/bf00724521] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Excised inside-out patches of vertebrate rod outer segment can support phototransduction. I have examined how ionic and metabolic conditions influence the functional properties of light-sensitive patches from Gekko gekko. I find that such patches retain a variable level of basal phosphodiesterase activity, which lowers the cyclic guanosine monophosphate (cGMP) concentration reaching the channels and reduces the dark current. The dose/response relationship for channel opening by cGMP varies among patches and this variability is only reduced by working in darkness with the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX), suggesting that it is only partially due to phosphodiesterase activity. MgATP or MgGTP, but not Mg or ATP separately, increase this activity but a kinase does not appear to be involved. Intracellular monovalent cations also influence dark current intensity and light response kinetics. With 5 mM MgGTP, 1 mM IBMX, and 144 mM Li+, Na+, K+, or Rb+, dark current intensity and recovery time follow the respective sequences K+ > Rb+ > Na+ > Li+ and K+ < Rb+ < Li+ < Na+. Without IBMX, a dark current develops with K+ but not with Na+. These effects are not due to altered channel permeability (P) [PLi+:Na+:K+:Rb+:guanidinium)/PNa+ = 0.84:1.00:1.01:1.09:0.42], or differential Mg2+ block, but to modulation of guanylate cyclase, which overcomes phosphodiesterase when the major cation is K+ but not when it is Na+.
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Affiliation(s)
- E A Ertel
- Department of Physiology and Biophysics, University of Washington, Seattle 98195
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125
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Glass TL, Sherwood JS. Phosphorylation of glucose by a guanosine-5'-triphosphate (GTP)-dependent glucokinase in Fibrobacter succinogenes subsp. succinogenes S85. Arch Microbiol 1994; 162:180-6. [PMID: 7979872 DOI: 10.1007/bf00314472] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Cell extracts of Fibrobacter succinogenes subsp. succinogenes S85 phosphorylated glucose with a GTP-dependent glucokinase. The enzyme showed little activity with ATP (12% of that with GTP). Of other phosphate donors tested, only dGTP and ITP gave high glucokinase activities. Dialyzed extracts required Mg+2 and K+ for maximal activity. In potassium phosphate buffer, glucokinase showed maximum activity at pH 7.5 with glucose-6-phosphate dehydrogenase as the coupling enzyme. In this assay, glucokinase was active with glucose (100%), 2-deoxy-D-glucose (40%), and mannose (20%). Partially purified glucokinase had a molecular weight of 82,000 and a pI of 4.82. Double-reciprocal plots of substrate concentration versus velocity were linear and the enzyme had apparent Km values of 55 microM for glucose and 72 microM for GTP. Dialyzed cell extracts of Fibrobacter intestinalis C1A also contained a GTP-dependent glucokinase that showed little activity with ATP. Potassium also stimulated the activity of this enzyme. These results suggest that this unusual glucokinase may be characteristic of the genus Fibrobacter.
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Affiliation(s)
- T L Glass
- Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo 58105
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126
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Larsen TM, Laughlin LT, Holden HM, Rayment I, Reed GH. Structure of rabbit muscle pyruvate kinase complexed with Mn2+, K+, and pyruvate. Biochemistry 1994; 33:6301-9. [PMID: 8193145 DOI: 10.1021/bi00186a033] [Citation(s) in RCA: 169] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The molecular structure of rabbit muscle pyruvate kinase, crystallized as a complex with Mn2+, K+, and pyruvate, has been solved to 2.9-A resolution. Crystals employed in the investigation belonged to the space group P1 and had unit cell dimensions a = 83.6 A, b = 109.9 A, c = 146.8 A, alpha = 94.9 degrees, beta = 93.6 degrees, and gamma = 112.3 degrees. There were two tetramers in the asymmetric unit. The structure was solved by molecular replacement, using as the search model the coordinates of the tetramer of pyruvate kinase from cat muscle [Muirhead, H., Claydon, D. A., Barford, D., Lorimer, C. G., Fothergill-Gilmore, L. A., Schiltz, E., & Schmitt, W. (1986) EMBO J.5, 475-481]. The amino acid sequence derived from the cDNA coding for the enzyme from rabbit muscle was fit to the electron density. The rabbit and cat muscle enzymes have approximately 94% sequence identity, and the folding patterns are expected to be nearly identical. There are, however, three regions where the topological models of the cat and rabbit pyruvate kinases differ. Mn2+ coordinates to the protein through the carboxylate side chains of Glu 271 and Asp 295. These two residues are strictly conserved in all known pyruvate kinases. In addition, the density for Mn2+ is connected to that of pyruvate, consistent with chelation through a carboxylate oxygen and the carbonyl oxygen of the substrate. The epsilon-NH2 of Lys 269 and the OH of Thr 327 lie on either side of the methyl group of bound pyruvate. Spherical electron density, assigned to K+, is located within a well-defined pocket of four oxygen ligands contributed by the carbonyl oxygen of Thr 113, O gamma of Ser 76, O delta 1 of Asn 74, and O delta 2 of Asp 112. The interaction of Asp 112 with the side chains of Lys 269 and Arg 72 may mediate, indirectly, monovalent cation effects on activity.
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Affiliation(s)
- T M Larsen
- Institute for Enzyme Research, Graduate School, University of Wisconsin-Madison 53705
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127
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Savage T, Hatch M, Croteau R. Monoterpene synthases of Pinus contorta and related conifers. A new class of terpenoid cyclase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41735-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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128
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Abstract
The coordination shell of Ca2+ ions in proteins contains almost exclusively oxygen atoms supported by an outer shell of carbon atoms. The bond-strength contribution of each ligating oxygen in the inner shell can be evaluated by using an empirical expression successfully applied in the analysis of crystals of metal oxides. The sum of such contributions closely approximates the valence of the bound cation. When a protein is embedded in a very fine grid of points and an algorithm is used to calculate the valence of each point representing a potential Ca(2+)-binding site, a typical distribution of valence values peaked around 0.4 is obtained. In 32 documented Ca(2+)-binding proteins, containing a total of 62 Ca(2+)-binding sites, a very small fraction of points in the distribution has a valence close to that of Ca2+. Only 0.06% of the points have a valence > or = 1.4. These points share the remarkable tendency to cluster around documented Ca2+ ions. A high enough value of the valence is both necessary (58 out of 62 Ca(2+)-binding sites have a valence > or = 1.4) and sufficient (87% of the grid points with a valence > or = 1.4 are within 1.0 A from a documented Ca2+ ion) to predict the location of bound Ca2+ ions. The algorithm can also be used for the analysis of other cations and predicts the location of Mg(2+)- and Na(+)-binding sites in a number of proteins. The valence is, therefore, a tool of pinpoint accuracy for locating cation-binding sites, which can also be exploited in engineering high-affinity binding sites and characterizing the linkage between structural components and functional energetics for molecular recognition of metal ions by proteins.
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Affiliation(s)
- M Nayal
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
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129
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Gatenby AA, Viitanen PV, Speth V, Grimm R. Identification, Cellular Localization, and Participation of Chaperonins in Protein Folding. MOLECULAR PROCESSES OF PHOTOSYNTHESIS 1994. [DOI: 10.1016/s1569-2558(08)60402-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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130
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Toney MD, Hohenester E, Cowan SW, Jansonius JN. Dialkylglycine decarboxylase structure: bifunctional active site and alkali metal sites. Science 1993; 261:756-9. [PMID: 8342040 DOI: 10.1126/science.8342040] [Citation(s) in RCA: 161] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The structure of the bifunctional, pyridoxal phosphate-dependent enzyme dialkylglycine decarboxylase was determined to 2.1-angstrom resolution. Model building suggests that a single cleavage site catalyzes both decarboxylation and transamination by maximizing stereoelectronic advantages and providing electrostatic and general base catalysis. The enzyme contains two binding sites for alkali metal ions. One is located near the active site and accounts for the dependence of activity on potassium ions. The other is located at the carboxyl terminus of an alpha helix. These sites help show how proteins can specifically bind alkali metals and how these ions can exert functional effects.
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Affiliation(s)
- M D Toney
- Department of Structural Biology, University of Basel, Switzerland
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131
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Kollmann R, Altendorf K. ATP-driven potassium transport in right-side-out membrane vesicles via the Kdp system of Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1143:62-6. [PMID: 8499455 DOI: 10.1016/0005-2728(93)90216-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The ATP-generating system described by Hugenholtz, J., Hong, J.-S. and Kaback, H.R. ((1981) Proc. Natl. Acad. Sci. USA 78, 3446-3449) has been used to synthesize ATP up to 1.8 mM in right-side-out membrane vesicles from Escherichia coli. This ATP level was sufficient to drive uptake of potassium ions via the Kdp-ATPase. In the kdp wild type strain about 110 nmoles K+/mg membrane protein were accumulated. This process was still partially sensitive to the well-known inhibitors of P-type ATPases, orthovanadate and bafilomycin B1.
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Affiliation(s)
- R Kollmann
- Universität Osnabrück, Fachbereich Biologie/Chemie, Arbeitsgruppe Mikrobiologie, Osnabrück, Germany
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132
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Perkins J, Gadd G. Caesium toxicity, accumulation and intracellular localization in yeasts. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/s0953-7562(09)80153-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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133
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Buurman ET, Herman PT, Teixeira de Mattos MJ, Neijssel OM. Replacement of potassium ions by ammonium ions in potassium-limited chemostat cultures of Candida utilis NCYC 321. FEMS Microbiol Lett 1993. [DOI: 10.1111/j.1574-6968.1993.tb05994.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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134
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Abee T, Siebers A, Altendorf K, Konings WN. Isolation and characterization of the high-affinity K(+)-translocating ATPase from Rhodobacter sphaeroides. J Bacteriol 1992; 174:6911-7. [PMID: 1400242 PMCID: PMC207370 DOI: 10.1128/jb.174.21.6911-6917.1992] [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: 12/26/2022] Open
Abstract
Cells of the purple nonsulfur bacterium Rhodobacter sphaeroides express a high-affinity K+ uptake system when grown in media with low K+ concentrations. A vanadate-sensitive, K(+)-stimulated and Mg(2+)-stimulated ATPase was purified from membranes of these cells by solubilization with decyl-beta-D-maltoside in the presence of Escherichia coli phospholipids followed by triazine-dye affinity chromatography. This primary transport system has a substrate specificity and an inhibitor sensitivity closely similar to those of the Kdp ATPase from E. coli and is composed of three subunits with molecular masses of 70.0, 43.5, and 23.5 kDa.
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Affiliation(s)
- T Abee
- Department of Microbiology, University of Groningen, Haren, The Netherlands
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135
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Shaw SM, Carrey EA. Regulation of the mammalian carbamoyl-phosphate synthetase II by effectors and phosphorylation. Altered affinity for ATP and magnesium ions measured using the ammonia-dependent part reaction. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 207:957-65. [PMID: 1499569 DOI: 10.1111/j.1432-1033.1992.tb17130.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have measured the 'core' mammalian carbamoyl-phosphate synthetase II (CPSII) activity, using NH4Cl as the nitrogen-donating substrate and trapping carbamoyl phosphate as urea through its reaction with ammonium ions. When ATP and magnesium ion concentrations are close to those found in the cell, the substrate saturation curves for ammonia and bicarbonate are hyperbolic, giving Km (NH3) values of 166 microM at high ATP concentrations and 26 microM at low ATP concentrations, while the Km (bicarbonate) is 1.4 mM at both ATP concentrations used. These values for the Km (NH3) are lower than previously reported for CPS II, and closer to the values for the mitochondrial counterpart. The Km for ammonia and bicarbonate are not altered by phosphorylation of the multienzyme polypeptide CAD, which contains the first three enzyme activities of pyrimidine biosynthesis. The CPS II activity is lower with an excess of either ATP or magnesium ions, causing the apparently sigmoid dependence of activity upon ATP concentration to be enhanced at low concentrations of free magnesium ions. The feedback inhibitor, UTP, acts by stabilising a state with a low affinity for magnesium ions and for ATP. In the presence of the activator, 5-phosphoribosyl diphosphate (PRibPP), the enzyme has a higher affinity for magnesium ions and thus the ATP dependence of the activity is hyperbolic. Phosphorylation of CAD similarly activates the CPS II enzyme by increasing the affinity for magnesium ions and by pushing the equilibrium away from the low-affinity UTP-stabilised state. Using our improved assay procedure, we observe a very large activation by PRibPP of carbamoylphosphate synthesis at low concentrations of magnesium ions, and we find that unlike UTP, the activator PRibPP is able to act on the phosphorylated enzyme.
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Affiliation(s)
- S M Shaw
- Department of Biochemistry, University of Dundee, Scotland
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136
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Kalabokis V, Bozzola J, Castellani L, Hardwicke P. A possible role for the dimer ribbon state of scallop sarcoplasmic reticulum. Dimmer ribbons are associated with stabilization of the Ca(2+)-free Ca-ATPase. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54742-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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137
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Eisenstein E. Cloning, expression, purification, and characterization of biosynthetic threonine deaminase from Escherichia coli. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)67668-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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138
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Lundberg P, Harmsen E, Ho C, Vogel HJ. Nuclear magnetic resonance studies of cellular metabolism. Anal Biochem 1990; 191:193-222. [PMID: 2085167 DOI: 10.1016/0003-2697(90)90210-z] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- P Lundberg
- Department of Biological Sciences, University of Calgary, Alberta, Canada
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139
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Golby P, Carver M, Jackson JB. Membrane ionic currents in Rhodobacter capsulatus. Evidence for electrophoretic transport of K+, Rb+ and NH4+. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 187:589-97. [PMID: 2406135 DOI: 10.1111/j.1432-1033.1990.tb15341.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
1. The cytoplasmic membrane ionic current of cells of Rhodobacter capsulatus, washed to lower the endogenous K+ concentration, had a non-linear dependence on the membrane potential measured during photosynthetic illumination. Treatment of the cells with venturicidin, an inhibitor of the H(+)-ATP synthase, increased the membrane potential and decreased the membrane ionic current at values of membrane potential below a threshold. 2. The addition of K+ or Rb+, but not of Na+, led to an increase in the membrane ionic current and a decrease in the membrane potential in either the presence or absence of venturicidin. Approximately 0.4 mM K+ or 2.0 mM Rb+ led to a half-maximal response. At saturating concentrations of K+ and Rb+, the membrane ionic currents were similar. The membrane ionic currents due to K+ and Rb+ were not additive. The K(+)-dependent and Rb(+)-dependent ionic currents had a non-linear relationship with membrane potential: the alkali cations only increased the ionic current when the membrane potential lay above a threshold value. The presence of 1 mM Cs+ did not lead to an increase in the membrane ionic current but it had the effect of inhibiting the membrane ionic current due to either K+ or Rb+. 3. Photosynthetic illumination in the presence of either K+ or Rb+, and weak acids such as acetate, led to a decrease in light-scattering by the cells. This was attributed to the uptake of potassium or rubidium acetate and a corresponding increase in osmotic strength in the cytoplasm. 4. The addition of NH4+ also led to an increase in membrane ionic current and to a decrease in membrane potential (half-maximal at 2.0 mM NH4+). The relationship between the NH4(+)-dependent ionic currents and the membrane potential was similar to that for K+. The NH4(+)-dependent and K(+)-dependent ionic current were not additive. However, illumination in the presence of NH4+ and acetate did not lead to significant light-scattering changes. The NH4(+)-dependent membrane ionic current was inhibited by 1 mM Cs+ but not by 50 microM methylamine. 5. It is proposed that the K(+)-dependent membrane ionic current is catalysed by a low-affinity K(+)-transport system such as that described in Rb. capsulatus [Jasper, P. (1978) J. Bacteriol. 133, 1314-1322]. The possibility is considered that, as well as Rb+, this transport system can also operate with NH4+. However, in our experimental conditions NH4+ uptake is followed by NH3 efflux.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- P Golby
- School of Biochemistry, University of Birmingham, England
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140
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Bossemeyer D, Borchard A, Dosch DC, Helmer GC, Epstein W, Booth IR, Bakker EP. K+-transport Protein TrkA of Escherichia coli Is a Peripheral Membrane Protein That Requires other trk Gene Products for Attachment to the Cytoplasmic Membrane. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84721-x] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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141
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142
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Hardwicke PM, Huvos P. Effect of K+, and other ligands on the thiol reactivity and tryptic cleavage pattern of scallop sarcoplasmic reticulum. J Muscle Res Cell Motil 1989; 10:229-44. [PMID: 2527247 DOI: 10.1007/bf01739813] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The kinetics of reaction of the thiol groups of both membranous and non-ionic detergent-solubilized Ca-ATPase of scallop sarcoplasmic reticulum towards 5,5'-dithiobis(2-nitrobenzoate) were greatly modified in different ways by the presence of the following combinations of ligands: Ca2+, EGTA (no Ca2+), (ATPMg2- + EGTA) and (ATP + Ca2+). K+ was found to influence greatly the pattern of reactivity of the thiol groups of the scallop Ca-ATPase, modifying the kinetics of reaction differently according to the types of other ligand present. While all the thiol groups on the non-ionic detergent-solubilized Ca-ATPase were available for reaction in the absence of K+, whatever the combination of ligands, in the presence of K+, several groups became completely unreactive towards the reagent. In some cases the rate of inactivation of Ca-ATPase activity could be related to the rates of reaction of different kinetic classes of thiol group, according to the ligands present. Large differences were also seen in the tryptic cleavage pattern in the presence of the different ligands, and K+ led to major modifications in the products of digestion in the absence of nucleotide. An 80 kDa tryptic fragment was observed, as with lobster Ca-ATPase but unlike rabbit skeletal muscle Ca-ATPase. A complete amino-acid analysis of the scallop Ca-ATPase was carried out. Differences in the non-polar amino-acid content from rabbit skeletal muscle Ca-ATPase may relate to the different lipid composition of the two membranes.
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Affiliation(s)
- P M Hardwicke
- Department of Medical Biochemistry, Southern Illinois University, Carbondale 62901-4409
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143
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Hafer J, Siebers A, Bakker EP. The high-affinity K+-translocating ATPase complex from Bacillus acidocaldarius consists of three subunits. Mol Microbiol 1989; 3:487-95. [PMID: 2527329 DOI: 10.1111/j.1365-2958.1989.tb00195.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Cells of the thermoacidophilic bacterium Bacillus acidocaldarius express a high-affinity K+-uptake system when grown at low external K+. A vanadate-sensitive, K+- and Mg2+-stimulated ATPase was partially purified from membranes of these cells by solubilization with a non-ionic detergent followed by ion-exchange chromatography of the extract. Combinations of non-denaturing and denaturing electrophoretic separation methods revealed that the ATPase complex consisted of three subunits with molecular weights almost identical to those of the KdpA, B and C proteins, which together form the Kdp high-affinity, K+-translocating ATPase complex of Escherichia coli. The affinity of the partially purified ATPase from B. acidocaldarius for its substrates K+ (Km 2-3 microM) and ATP (Km 80 microM), its stimulation by various divalent cations, and its inhibition by vanadate (Ki 1-2 microM), bafilomycin A1 (Ki 20 microM), DCCD (Ki 200 microM) or Ca2+ were also similar to those of the E. coli enzyme, indicating that the two K+-translocating ATPases have almost identical properties.
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Affiliation(s)
- J Hafer
- Abteilung Mikrobiologie, Universität Osnabrück, FRG
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144
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van Poelje PD, Snell EE. Amine cations promote concurrent conversion of prohistidine decarboxylase from Lactobacillus 30a to active enzyme and a modified proenzyme. Proc Natl Acad Sci U S A 1988; 85:8449-53. [PMID: 3250558 PMCID: PMC282475 DOI: 10.1073/pnas.85.22.8449] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Activation of prohistidine decarboxylase (pi 6) from Lactobacillus 30a proceeds by an intramolecular, pH- and monovalent cation-dependent reaction in which its constituent pi chains are cleaved nonhydrolytically between Ser-81 and Ser-82 with loss of NH3 and conversion of Ser-82 to the pyruvoyl residue of active histidine decarboxylase (alpha beta)6. Amines with pKa values more than 7.0 substitute for K+ or NH4+ in the activation of prohistidine decarboxylase, but they also catalyze its inactivation in a competing reaction, pi 6----pi'6. Sequence analysis of the appropriate tryptic peptide from amine-inactivated prohistidine decarboxylase established that inactivation results from conversion of Ser-82 of the pi chain to an aminoacrylate residue. The inactivated proenzyme (pi'6) does not form histidine decarboxylase; this fact eliminates one of two postulated mechanisms of activation and, thus, favors activation by beta-elimination of the acyl group of an intermediate ester formed between Ser-81 and Ser-82. L-Histidine is bound by the proenzyme (Kd = 1.7 x 10(-4) M) and is an effective activator; one binding site is present per pi subunit. K+, NH4+, and Na+ competitively inhibit (Ki values = 2.8-4.4 x 10(-3) M) activation by histidine. The data suggest the presence of two classes of monovalent cation binding sites on prohistidine decarboxylase: one (near Ser-82) is readily saturable and one is unsaturable even by 2.4 M K+.
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Affiliation(s)
- P D van Poelje
- Department of Chemistry, University of Texas, Austin 78712
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145
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Shimomura Y, Kuntz MJ, Suzuki M, Ozawa T, Harris RA. Monovalent cations and inorganic phosphate alter branched-chain alpha-ketoacid dehydrogenase-kinase activity and inhibitor sensitivity. Arch Biochem Biophys 1988; 266:210-8. [PMID: 3178224 DOI: 10.1016/0003-9861(88)90252-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Potassium ion protects the branched-chain alpha-ketoacid dehydrogenase complex against inactivation by thermal denaturation and protease digestion. Rubidium was effective but sodium and lithium were not, suggesting that the ionic size of the cation is important for stabilization of the enzyme. Thiamine pyrophosphate stabilization of the complex [Danner, D. J., Lemmon, S. K., and Elsas, S. J. (1980) Arch. Biochem. Biophys. 202, 23-28] was found dependent on the presence of potassium ion. Studies with resolved components indicate that the thiamine pyrophosphate-dependent enzyme of the complex, i.e., the 2-oxoisovalerate dehydrogenase (lipoamide) (EC 1.2.4.4), is the component stabilized by potassium ion. Branched-chain alpha-ketoacid dehydrogenase-kinase activity measured by inactivation of the branched-chain alpha-ketoacid dehydrogenase complex was maximized at a potassium ion concentration of 100 mM. Stimulation of kinase activity was also found with rubidium ion but not with lithium and sodium ions. All salts tested increased the efficiency of inactivation by phosphorylation, i.e., decreased the degree of enzyme phosphorylation required to cause inactivation of the complex. The effectiveness and efficacy of alpha-chloroisocaproate as an inhibitor of branched-chain alpha-ketoacid dehydrogenase kinase were enhanced by the presence of monovalent cations, and further increased by inorganic phosphate. These findings suggest that monovalent cations and anions, particularly potassium and phosphate, cause structural changes in the dehydrogenase-kinase complex that alter its susceptibility to phosphorylation and responsiveness to kinase inhibitors.
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Affiliation(s)
- Y Shimomura
- Department of Biochemistry, Indiana University School of Medicine, Indianapolis 46223
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146
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Wehbie RS, Punekar NS, Lardy HA. Rat liver gamma-butyrobetaine hydroxylase catalyzed reaction: influence of potassium, substrates, and substrate analogues on hydroxylation and decarboxylation. Biochemistry 1988; 27:2222-8. [PMID: 3378057 DOI: 10.1021/bi00406a062] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Interaction of rat liver gamma-butyrobetaine hydroxylase (EC 1.14.11.1) with various ligands was studied by following the decarboxylation of alpha-ketoglutarate, formation of L-carnitine, or both. Potassium ion stimulates rat liver gamma-butyrobetaine hydroxylase catalyzed L-carnitine synthesis and alpha-ketoglutarate decarboxylation by 630% and 240%, respectively, and optimizes the coupling efficiency of these two activities. Affinities for alpha-ketoglutarate and gamma-butyrobetaine are increased in the presence of potassium. gamma-Butyrobetaine hydroxylase catalyzed decarboxylation of alpha-ketoglutarate was dependent on the presence of gamma-butyrobetaine, L-carnitine, or D-carnitine in the reaction and exhibited Km(app) values of 29, 52, and 470 microM, respectively. gamma-Butyrobetaine saturation of the enzyme indicated a substrate inhibition pattern in both the assays. Omission of potassium decreased the apparent maximum velocity of decarboxylation supported by all three compounds by a similar percent. beta-Bromo-alpha-ketoglutarate supported gamma-butyrobetaine hydroxylation, although less effectively than alpha-ketoglutarate. The rat liver enzyme was rapidly inactivated by 1 mM beta-bromo-alpha-ketoglutarate at pH 7.0. This inactivation reaction did not show a rate saturation with increasing concentrations of beta-bromo-alpha-ketoglutarate. None of the substrates or cofactors, including alpha-ketoglutarate, protected the enzyme against this inactivation. Unlike beta-bromo-alpha-ketoglutarate, beta-mercapto-alpha-ketoglutarate did not replace alpha-ketoglutarate as a cosubstrate. Both beta-mercapto-alpha-ketoglutarate and beta-glutathione-alpha-ketoglutarate were noncompetitive inhibitors with respect to alpha-ketoglutarate.
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Affiliation(s)
- R S Wehbie
- Institute for Enzyme Research, University of Wisconsin, Madison 53705
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147
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Potassium Estimation, Uptake, and Its Role in the Physiology and Metabolism of Flowering Plants. INTERNATIONAL REVIEW OF CYTOLOGY 1988. [DOI: 10.1016/s0074-7696(08)61851-3] [Citation(s) in RCA: 105] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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148
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Bakker EP, Borchard A, Michels M, Altendorf K, Siebers A. High-affinity potassium uptake system in Bacillus acidocaldarius showing immunological cross-reactivity with the Kdp system from Escherichia coli. J Bacteriol 1987; 169:4342-8. [PMID: 2957359 PMCID: PMC213750 DOI: 10.1128/jb.169.9.4342-4348.1987] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
During growth with low levels of K+, Bacillus acidocaldarius expressed a high-affinity K+ uptake system. The following observations indicate that this system strongly resembles the Kdp-ATPase of Escherichia coli: (i) its high affinity for K+ (Km of 20 microM or below); (ii) its poor transport of Rb+; (iii) the enhanced ATPase activity of membranes derived from cells grown with low levels of K+ (this activity was stimulated by K+ and inhibited by vanadate); (iv) the expression of an extra protein with a molecular weight of 70,000 in cells grown with low levels of K+; and (v) the immunological cross-reactivity of this 70,000-molecular-weight protein with antibodies against the catalytic subunit B of the E. coli Kdp system. Antibodies against the complete E. coli Kdp system, which immunoprecipitated the whole E. coli KdpABC complex, almost exclusively precipitated the 70,000-molecular-weight protein from detergent-solubilized B. acidocaldarius membranes. The possibility that the B. acidocaldarius Kdp system consists of a single, KdpB-type subunit is discussed.
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149
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Fischer RS, Rubin JL, Gaines CG, Jensen RA. Glyphosate sensitivity of 5-enol-pyruvylshikimate-3-phosphate synthase from Bacillus subtilis depends upon state of activation induced by monovalent cations. Arch Biochem Biophys 1987; 256:325-34. [PMID: 3111378 DOI: 10.1016/0003-9861(87)90453-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The 5-enol-pyruvylshikimate-3-phosphate (EPSP) synthase from Bacillus subtilis was activated by monovalent cations, catalytic activity being negligible in the absence of monovalent cations. The order of cation effectiveness (NH4+ greater than K+ greater than Rb+ greater than Na+ = Cs+ = Li+) indicated that the extent of activation was directly related to the unhydrated cation radius. Ammonium salts, at physiological concentrations, were dramatically more effective than other cations. Activation by ammonium was instantaneous, was not influenced by the counter ion, and gave a hyperbolic saturation curve. Hill plots did not show detectable cooperativity in the binding of ammonium. Double-reciprocal plots indicated that ammonium increases the maximal velocity and decreases the apparent Michaelis constants of EPSP synthase with respect to both phosphoenol pyruvate (PEP) and shikimate 3-phosphate (S3P). A direct relationship between sensitivity to inhibition by glyphosate and the activation state of EPSP synthase was demonstrated. Hill plots indicated a single value for glyphosate binding throughout the range of ammonium activation. Double-reciprocal plots of substrate saturation data obtained with ammonium-activated enzyme in the presence of glyphosate showed glyphosate to behave as a competitive inhibitor with respect to PEP and as a mixed-type inhibitor relative to S3P. The increased glyphosate sensitivity of ammonium-activated EPSP synthase is attributed to a lowering of the inhibitor constant of glyphosate with respect to PEP. Erroneous underestimates of sensitivities of some bacterial EPSP synthases to inhibition by glyphosate may result from failure to recognize cation requirements of EPSP synthases.
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150
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Almuaibed AM, Townshend A. Determination of acetaldehyde by flow injection analysis with soluble or immobilized aldehyde dehydrogenase. Anal Chim Acta 1987. [DOI: 10.1016/s0003-2670(00)85004-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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