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1.
Metal chelates in the storage and transport of neurotransmitters: formation of mixed ligand chelates of Mg 2+ -ATP with biogenic amines 总被引:2,自引:0,他引:2
Abstract— Quantitative studies on the interactions of adenosine-triphosphate and several biogenic amines with magnesium ion have been carried out in an attempt to correlate the thermodynamic stabilities of the metal-binding of the amines with the in vivo affinities of the amines for granule-binding. Equilibrium data indicate that in each of the ternary chelate systems (viz. Mg2+-ATP-amine), the predominant reaction in the pH range 3.0–7.0 is the formation of a magnesium-ATP chelate with a stability constant, log KML=3.22 ± 0.02. Each of the biogenic amines coordinates with Mg2+-ATP system in the pH range 7.0–10.5 to form the mixed ligand chelate (or ternary chelate), Mg2+-ATP-amine(1:1:1). The stability constants for the binding of the amines with Mg2+-ATP are: (i) norepinephrine (NE) = 2.34 ± 0.32; (ii) epinephrine (E) = 2.95 ± 0.08; (iii) dopamine (DA) = 3.05 ± 0.06; (iv) octopamine (OA) = 1.93 ± 0.12; (v) 6-hydroxydopamine (6-HDA) = 2.42 ± 0.14; (vi) 3-methoxynorephedrine (MeN) =2.76 ± 0.09; (vii) amphetamine (AA) =2.09 ± 0.05; (viii) tyramine (TA) = 2.60 ± 0.04; (ix) phenylethylamine (PEA) = 0. A general correlation is indicated between the stability constants (binding strengths) of the amine chelates and the metal-binding functionalities of the amines on the one hand and their vesicular binding characteristics in in vivo systems on the other (Carlsson and Waldeck , 1966). The Mg2+-ATP-dependant amine storage mechanism of KIRSHNER (1962a;b) and Carlsson , Hillårp and Waldeck (1963) is discussed both in the light of the data on metal chelate stability and of a significant modification of metal coordination hypothesis. 相似文献
2.
Toru Shimizu Masahiro Hatano 《Biochemical and biophysical research communications》1982,104(2):720-726
25Mg NMR spectroscopy was first applied to the ternary complexes consisting of Mg2+, ATP, ADP and creatine kinase. The 25Mg NMR spectra of the Mg2+-ATP (or ADP) complex are remarkably broadened in the ternary Mg2+-ATP(or ADP)-creatine kinase complex in contrast with previous prediction. From temperature dependence of the spectra of the protein-bound ion, it is suggested that Mg2+ of the protein-bound Mg2+-ATP(or ADP) complex is not in the fast exchange regime. The 25Mg NMR signal of the transition state analogue complex is narrower and less temperature-dependent than those of the ternary complex, suggesting that Mg2+ in the transition state analogue complex is in a more symmetrical environment or exchanges slower than that of the ternary complex. 相似文献
3.
R. Barrett-Jolley A. Comtois N.W. Davies P.R. Stanfield N.B. Standen 《The Journal of membrane biology》1996,152(2):111-116
We investigated the action of adenosine and GTP on KATP channels, using inside-out patch clamp recordings from dissociated single fibers of rat flexor digitorum brevis (FDB) skeletal
muscle. In excised patches, KATP channels could be activated by a combination of an extracellular adenosine agonist and intracellular Mg2+-ATP and GTP or GTP-γ-S. The activation required hydrolyzable ATP and could be partially reversed with Mg2+, suggesting that it may involve a G-protein dependent phosphorylation of KATP channels. We found that KATP channels of the rat FDB could not be activated by Mg2+-ATP alone or by Mg2+-ATP in the presence of extracellular adenosine. Patches whose channel activity had been `rundown' by Ca2+ could not be recovered by adenosine, GTP or Mg2+-ATP. KATP channels activated by adenosine receptor agonists had a similar ATP sensitivity to those under control conditions; but adenosine
appears to be able to switch these KATP channels from an inactive to an active mode.
Received: 29 December 1995/Revised: 22 March 1996 相似文献
4.
Elisa Biondi Raghav R. Poudyal Joshua C. Forgy Andrew W. Sawyer Adam W. R. Maxwell Donald H. Burke 《Nucleic acids research》2013,41(5):3327-3338
The chemical strategies used by ribozymes to enhance reaction rates are revealed in part from their metal ion and pH requirements. We find that kinase ribozyme K28(1-77)C, in contrast with previously characterized kinase ribozymes, requires Cu2+ for optimal catalysis of thiophosphoryl transfer from GTPγS. Phosphoryl transfer from GTP is greatly reduced in the absence of Cu2+, indicating a specific catalytic role independent of any potential interactions with the GTPγS thiophosphoryl group. In-line probing and ATPγS competition both argue against direct Cu2+ binding by RNA; rather, these data establish that Cu2+ enters the active site within a Cu2+•GTPγS or Cu2+•GTP chelation complex, and that Cu2+•nucleobase interactions further enforce Cu2+ selectivity and position the metal ion for Lewis acid catalysis. Replacing Mg2+ with [Co(NH3)6]3+ significantly reduced product yield, but not kobs, indicating that the role of inner-sphere Mg2+ coordination is structural rather than catalytic. Replacing Mg2+ with alkaline earths of increasing ionic radii (Ca2+, Sr2+ and Ba2+) gave lower yields and approximately linear rates of product accumulation. Finally, we observe that reaction rates increased with pH in log-linear fashion with an apparent pKa = 8.0 ± 0.1, indicating deprotonation in the rate-limiting step. 相似文献
5.
R Nakon 《Analytical biochemistry》1979,95(2):527-532
Formation (affinity) constants for 1:1 complexes of N-(2-acetamido)iminodiacetic acid (ADAH2) with Ca(II), Mg(II), Mn(II), Zn(II), Co(II), Ni(II), and Cu(II) have been determined. Probable structures of the various metal chelates existing in solution are discussed. Values for the deprotonation of the amide group in [Cu(ADA)] and subsequent hydroxo complex formation are also reported. The use of ADA as a buffer is considered in terms of metal buffers complexes which can be formed at physiological pH, i.e., at pH 7.0 there is essentially no free metal ion in 1:1 M2+ to ADA solutions. 相似文献
6.
Jakab NI Jancsó A Gajda T Gyurcsik B Rockenbauer A 《Journal of inorganic biochemistry》2008,102(7):1438-1448
The copper(II), nickel(II) and zinc(II) binding ability of the multi-histidine peptide N-acetyl-His-Pro-His-His-NH2 has been studied by combined pH-potentiometry and visible, CD and EPR spectroscopies. The internal proline residue, preventing the metal ion induced successive amide deprotonations, resulted in the shift of this process toward higher pH values as compared to other peptides. The metal ions in the parent [ML]2+ complexes are exclusively bound by the three imidazole side chains. In [CuH−1L]+, formed between pH 6-8, the side chains of the two adjacent histidines and the peptide nitrogen between them are involved in metal ion binding. The next deprotonation results in the proton loss of the coordinated water molecule (CuH−1L(OH)). The latter two species exert polyfunctional catalytic activity, since they possess superoxide dismutase-, catecholase- (the oxidation of 3,5-di-tert-butylcatechol) and phosphatase-like (transesterification of the activated phosphoester 2-hydroxypropyl-4-nitrophenyl phosphate) properties. On further increase of the pH rearrangement of the coordination sphere takes place leading to the [CuH−3L]− species, the deprotonated amide nitrogen displaces a coordinated imidazole nitrogen from the equatorial position of the metal ion. The shapes of the visible and CD spectra reflect a distorted arrangement of the donor atoms around the metal ion. In presence of zinc(II) the species [ZnL]2+ forms only above pH 6, which is shortly followed by precipitation. On the other hand, the [NiL]2+ complex is stable over a wide pH range, its deprotonation takes place only above pH 8. At pH 10 an octahedral NiH−2L species is present at first, which transforms slowly to a yellow square planar complex. 相似文献
7.
José A. Teruel José Tudela Francisco Garcia Carmona Juan C. Gomez Fernandez Francisco Garcia Canovas 《Journal of bioenergetics and biomembranes》1987,19(4):383-396
The (Ca2+-Mg2+)-ATPase from sarcoplasmic reticulum presents negative cooperativity for the hydrolysis of Mg2+-ATP at different concentration ranges of this substrate. A kinetic model is proposed according to which Mg2+-ATP may bind to three different enzymatic species present during the catalytic cycle, E (K
1=1 µM), EP.Ca2 (K
9=500 µM) and *EP (K
7=20 µM), accelerating the release of Pi. The fact that each of these species has a different affinity for Mg2+-ATP allows a significant enhancement of the rate of Pi release to the medium at the different ranges of Mg2+-ATP concentration where the enzyme shows a kinetic cooperativity. The kinetic analysis of this mechanism yields an equation which is a ratio of two cubic polynomials (3:3 rate equations) with respect to Mg2+-ATP and which may explain the negative cooperativity of the enzyme at different concentration ranges of Mg2+-ATP.Abbreviations: EGTA, ethylene glycol bis(-aminoethylether)-N,N,N,N-tetraacetic acid; I.U., international units; piruvate kinase (EC 2.7.1.40); lactate dehydrogenase (EC 1.1.1.27); ATP phosphohydrolase (EC 3.8.1.3). 相似文献
8.
《Phytochemistry》1986,26(1):65-69
In the presence of K+, the hydrolysis of ATP catalysed by the ATPase of corn plasma membrane showed negative cooperative kinetics. When the complexes of ATP and Mg2+, Mn2+, Ca2+ or Cd2+ were used as substrates, the catalysed hydrolysis changed to follow simple Michaelis-Menten kinetics. However, this change was not observed with Zn2+-ATP as the substrate. A substantial enhancement of the hydrolysis was observed only when the complexes of Mg2+ and Mn2+ were used. Kinetic parameter determination indicated that the enzyme exhibited a similar binding property but a different catalytic efficiency to Mg2+, Mn2+ and Ca2+-ATP. The enzyme formed a more stable but less reactive complex with Cd2+-ATP. The presence of aluminium ions competitively inhibited the membrane-catalysed hydrolysis of Mg2+-ATP, but showed no effect when free ATP was the substrate. This finding suggested that aluminium might bind in the vicinity of the Mg2+ of Mg2+-ATP in the active site of the enzyme. On the basis of these observed inhibitory effects, possible origins of metal ion toxicity to root plasma membrane ATPase activity are discussed. 相似文献
9.
A. Dei 《Inorganica chimica acta》1975,12(1):79-83
The open-chain, potentially, pentadentate, ligan 1,11-bis(dimethylamino)-3,6,9-trimethyl-3,6,9,-triazaundecane (Me7tetren) forms a series of metal complexes having the general formula [M(Me7tetren)]Y2 (Y = 1, M = Co, Ni; Y = ClO4, M = Co, Ni, Cu, Zn). On the basis of their physical properties, it is suggested that all these compounds contains isostructural five-coordinate [M(Me7tetren)]2+ cations, the ligand acting as pentadentate. These complexes react in solution with thiocyanate ion to give mono- and, with exception of copper(II), di-thiocyanato five- and six-co-ordinate derivatives. Mono-thiocyanato derivatives of cobalt(II), nickel(II) and zinc(II) have been isolated as tetraphenylborate salts. Cobalt(II) and nickel (II) di-thiocyanato derivatives have been also isolated. Results are discussed in terms of the steric requirements of the ligand and electronic properties of the metal ions. 相似文献
10.
The photoreactions of tris(2,2′-bipyridine)nickel(II) complex, Ni(II)(bpy3)2+ were studied and compared with that of the photoreactions of 2,2′-bipyridine ligand. Continuous photolysis of the complex shows that the photodecomposition corresponds to the absorption of light by the complex in the ligand centered excited state. Flash photolysis of the complex using a 248 nm excimer laser yields bipyridine cation radical and solvated electron as transients. Absorption spectra of the transient observed for the complex is found to be similar to that observed for the ligand on flash excitation using a 248 nm laser suggesting that the transients observed in the case of complex is due to the coordinated bipyridine in the complex. The formation of solvated electron is observed to be monophotonic and that of the bipyridine cation radical is found to be a biphotonic process. Significant change in Ni-N bond distance upon oxidation of Ni(bpy3)2+ ion when compared to that observed in nickel(II)tetraazamacrocyclic complexes suggests that the formation of the trivalent complex by photolysis is not favored for the Ni(bpy3)2+ ion and CTTS excited state in the complex is not observed in the present system. 相似文献
11.
Malarkey CS Wang G Ballicora MA Mota de Freitas DE 《Biochemical and biophysical research communications》2008,372(4):866-869
The function of guanine nucleotide binding (G) proteins is Mg2+ dependent with guanine nucleotide exchange requiring higher metal ion concentration than guanosine 5′-triphosphate hydrolysis. It is unclear whether two Mg2+ binding sites are present or if one Mg2+ binding site exhibits different affinities for the inactive GDP-bound or the active GTP-bound conformations. We used furaptra, a Mg2+-specific fluorophore, to investigate Mg2+ binding to α subunits in both conformations of the stimulatory (Gsα) and inhibitory (Giα1) regulators of adenylyl cyclase. Regardless of the conformation or α protein studied, we found that two distinct Mg2+ sites were present with dissimilar affinities. With the exception of Gsα in the active conformation, cooperativity between the two Mg2+ sites was also observed. Whereas the high affinity Mg2+ site corresponds to that observed in published X-ray structures of G proteins, the low affinity Mg2+ site may involve coordination to the terminal phosphate of the nucleotide. 相似文献
12.
An ATPase activity stimulated by divalent ions (Mg2+, Ca2+, Mn2+, Zn2+) has been observed in intact hamster fibroblasts cultured in vitro (BHK line). Such activity has been determined by the incubation (30 min at 37°C) of washed cell suspensions (about 1 mg of proteins) in a medium containing 100 mM NaCl, 20 mM KCl, 15 mM Tris—HCl (pH 7.4), 10 mM NaHCO3, 5 mM glucose and equimolar concentrations of ATP and divalent cation. Mg2+-ATPase activity is insensitive to ouabain and lacks specificity towards nucleoside triphosphate substrates. AMP and ADP are not hydrolyzed under these conditions. Apparent Km of 0.76 mM and Vmax of 1.46 μmol Pi · mg proteins?1 · h?1 have been calculated for Mg-ATP complex. This ATPase is an ectoenzyme, therefore its activity could be used as a suitable index of the action of chemicals like chromium compounds known for their cytotoxic effects on membrane functions.Salts of trivalent (CrCl3) and hexavalent (K2Cr2O7) chromium at concentrations ranging from 1 mM to 5 mM inhibit Mg2+-ATPase. The inhibition by K2Cr2O7 is observed after pretreatment of the cells with this compound followed by its absence from the assay medium “per se” for Mg2+-ATPase, and it is referred to the alterations of membrane bound enzyme structures by the oxidizing hexavalent chromium. The inhibition by CrCl3 is mainly evident when this compound is present in the incubation medium, and is referred to the interaction of trivalent chromium with Mg2+-ATP as it is partially reversed by increasing Mg2+-ATP concentration. 相似文献
13.
Mithramycin (Mith) forms a drug-metal complex with a 2:1 stoichiometry by chelation with a Ni(II) ion, which was determined using circular dichroism spectroscopy. Mith exhibits an increased affinity (~55 fold) for Ni(II) in the presence of DNA compared to the absence of DNA, suggesting that DNA acts as an effective template to facilitate chelation. Also, we characterized the DNA-acting properties of a Ni(II) derivative of Mith. Kinetic analysis using surface plasmon resonance and UV melting studies revealed that NiII(Mith)2 binds to duplex DNA with a higher affinity compared to MgII(Mith)2. The thermodynamic parameters revealed a higher free energy of formation for duplex DNA in the presence of NiII(Mith)2 compared to duplex DNA in the presence of MgII(Mith)2. The results of a DNA-break assay indicated that NiII(Mith)2 is capable of promoting one-strand cleavage of plasmid DNA in the presence of hydrogen peroxide; the DNA cleavage rate of NiII(Mith)2 was calculated to be 4.1 × 10?4 s?1. In cell-based experiments, NiII(Mith)2 exhibited a more efficient reduction of c-myc and increased cytotoxicity compared to Mith alone because of its increased DNA-binding and cleavage activity. The evidence obtained in this study suggests that the biological effects of NiII(Mith)2 require further investigation in the future. 相似文献
14.
Ohishi H Odoko M Zhou DY Tozuka Y Okabe N Nakatani K Ishida T Grzeskowiak K 《Biochemical and biophysical research communications》2008,368(2):382-387
In crystals of complexes of thermine and d(CGCGCG)2 molecules grown at 4, 10, and 20 °C, the numbers of thermine molecules connected to the DNA molecule were dependent on the temperature of the crystallization. Two molecules of thermine and one Mg2+ ion were connected to DNA molecule when thermine and d(CGCGCG)2 were co-crystallized at 4 and at 20 °C. When an increased concentration of magnesium and thermine molecules were co-crystallized with d(CGCGCG)2 molecules at 10 °C, three Mg2+ ions and only one thermine molecule were bound with a d(CGCGCG)2 molecule. The number of polyamines and of Mg2+ ions connected to DNA was dependent on the atomic values of the polyamine and of the metal ion. The binding of more Mg2+ ions occurred when the atomic value of Mg2+ exceeded that of the corresponding mono- or polyamine, and when the Mg2+ ion concentration was elevated. Furthermore, this study is the first documentation of a naturally occurring polyamine bound to the minor groove of DNA in a crystal structure. 相似文献
15.
Feng Gao Hui Chao Jin-Quan Wang Yi-Xian Yuan Bin Sun Yuan-Fang Wei Bin Peng Liang-Nian Ji 《Journal of biological inorganic chemistry》2007,12(7):1015-1027
Many antitumor drugs act as topoisomerase inhibitors, and the inhibitions are usually related to DNA binding. Here we designed
and synthesized DNA-intercalating Ru(II) polypyridyl complexes Δ--[Ru(bpy)2(uip)]2+ and Λ-[Ru(bpy)2(uip)]2+ (bpy is 2,2′-bipyridyl, uip is 2-(5-uracil)-1H-imidazo[4,5-f][1,10]phenanthroline). The DNA binding, photocleavage, topoisomerase inhibition, and cytotoxicity of the complexes were studied.
As we expected, the synthesized Ru(II) complexes can intercalate into DNA base pairs and cleave the pBR322 DNA with high activity
upon irradiation. The mechanism studies reveal that singlet oxygen (1O2) and superoxide anion radical (O2•−) may play an important role in the photocleavage. The inhibition of topoisomerases I and II by the Ru(II) complexes has been
studied. The results suggest that both complexes are efficient inhibitors towards topoisomerase II by interference with the
DNA religation and direct topoisomerase II binding. Both complexes show antitumor activity towards HELA, hepG2, BEL-7402,
and CNE-1 tumor cells.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
《Inorganica chimica acta》1987,130(2):157-162
The acid-catalysed dissociation rate constants for PbEGTA2− and CuEGTA2− complexes (where EGTA is ethylenebis(oxyethylenenitrilo) tetraacetic acid) were measured in acetic acid-acetate buffer medium (pH: 3.0–4.8) and perchloric acid solutions ([H+] = 0.05–0.15 M), respectively, at a constant ionic strength of 0.15 (NaClO4). The rate laws shown by the lead(II) and copper(II) complexes are of the form, Rate = {kd + kH[H+]}[complex] and Rate = {kd + kH2[H+]2}[complex], respectively. Enthalpy and entropy of activation for acid-independent and acid-catalysed pathways for both the complexes were obtained by the temperature-dependence studies of resolved rate constants in the 16–45°C range. The rate of dissociation of PbEGTA2− is not enhanced by increasing the concentration of acetate ion in the buffer, and the amount of total electrolyte in the reaction mixture has no pronounced effect on the dissociation rates of their the lead(II) or copper(II) complex. Attempts to study the kinetics of stepwise ligand unwrapping in the binuclear Cu2EGTA complex were unsuccessful due to the extremely rapid dissociation of this complex to yield mononuclear CuEGTA2−. 相似文献
17.
Susmita Bandyopadhyay G.N. Mukherjee Andrea Cantoni Siddhartha Chaudhuri 《Inorganica chimica acta》2004,357(12):3563-3573
Combined pH-metric, UV-Vis, 1H NMR and EPR spectral investigations on the complex formation of M(II) ions (M=Co, Ni, Cu and Zn) with N-(2-benzimidazolyl)methyliminodiacetic acid (H2bzimida, hereafter H2L) in aqueous solution at a fixed ionic strength, I=10−1 mol dm−3, at 25 ± 1 °C indicate the formation of M(L), M(H−1L)− and M2(H−1L)+ complexes. Proton-ligand and metal-ligand constants and the complex formation equilibria have been elucidated. Solid complexes, [M(L)(H2O)2] · nH2O (n=1 for M = Co and Zn, n=2 for M = Ni) and {Cu (μ-L) · 4H2O}n, have been isolated and characterized by elemental analysis, spectral, conductance and magnetic measurements and thermal studies. Structures of [Ni(L)(H2O)2] · 2H2O and {Cu(μ-L) · 4H2O}n have been determined by single crystal X-ray diffraction. The nickel(II) complex exists in a distorted octahedral environment in which the metal ion is coordinated by the two carboxylate O atoms, the amino-N atom of the iminodiacetate moiety and the pyridine type N-atom of the benzimidazole moiety. Two aqua O atoms function as fifth and sixth donor atoms. The copper(II) complex is made up of interpenetrating polymeric chains of antiferromagnetically coupled Cu(II) ions linked by carboxylato bridges in syn-anti (apical-equatorial) bonding mode and stabilized via interchain hydrogen bonds and π-π stacking interactions. 相似文献
18.
19.
Lin Cheng BingGuo Wei Ling Ling He Ling Mao Jie Zhang JinXiang Ceng DeRong Kong ChaDan Chen HanFeng Cui Nian Hong Hao Fan 《Analytical biochemistry》2017
A novel “off-On” electrogenerated chemiluminescence (ECL) biosensor has been developed for the detection of mercury(II) based on molecular recognition technology. The ECL mercury(II) biosensor comprises two main parts: an ECL substrate and an ECL intensity switch. The ECL substrate was made by modifying the complex of Ruthenium(II) tris-(bipyridine)(Ru(bpy)32+)/Cyclodextrins-Au nanoparticles(CD-AuNps)/Nafion on the surface of glass carbon electrode (GCE), and the ECL intensity switch is the single hairpin DNA probe designed according to the “molecular recognition” strategy which was functionalized with ferrocene tag at one end and attached to Cyclodextrins (CD) on modified GCE through supramolecular noncovalent interaction. We demonstrated that, in the absence of Hg(II) ion, the probe keeps single hairpin structure and resulted in a quenching of ECL of Ru(bpy)32+. Whereas, in the presence of Hg(II) ion, the probe prefers to form the T-Hg(II)-T complex and lead to an obvious recovery of ECL of Ru(bpy)32+, which provided a sensing platform for the detection of Hg(II) ion. Using this sensing platform, a simple, rapid and selective “off-On” ECL biosensor for the detection of mercury(II) with a detection limit of 0.1 nM has been developed. 相似文献
20.
Crystallographic and magnetic studies have been performed on the complex, [{CuCl}2(μ-tppz)][PF6]2, where tppz is 2,3,5,6-tetra-2-pyridinylpyrazine. The crystal structure revealed an infinite, ionic chain wherein Cu(II) ions are respectively above and below the plane of the pyrazine moiety of the bridging tppz ligand with the pyridine moieties moving out of the pyrazine plane in order to coordinate to Cu(II). Each chloride ligand bonds equatorially to Cu(II) in a [{CuCl}2(μ-tppz)]2+ ion and axially to a neighboring [{CuCl}2(μ-tppz)]2+ ion so as to form a one-dimensional chain in the solid state. The temperature-dependent magnetic susceptibilitity could be satisfactorily fitted by using a modified Bleaney-Bowers expression (for H = −JSa · SbJ = −5.6 cm−1 and g = 2.16) where the exchange interaction is suggested to involve the orbitals of the tppz ligand. 相似文献