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PubMed1994

The Saccharomyces cerevisiae copper transport protein (Ctr1p). Biochemical characterization, regulation by copper, and physiologic role in copper uptake.

The CTR1 gene of Saccharomyces cerevisiae encodes a protein required for high affinity copper uptake. The protein is expressed on the plasma membrane, is heavily glycosylated with O-linkages, and exists as an oligomer in vivo. The transcript abundance is strongly regulated by copper availability, being induced by copper deprivation and repressed by copper excess. Regulation occurs at very low, nontoxic levels of available copper and is independent of ACE1, the trans-inducer of yeast metallothionein. Expression of Ctr1p is limiting for copper uptake, since overexpression from a 2 mu high copy number plasmid increases copper uptake. Mutations in CTR1 result in altered cellular responses to extracellular copper, demonstrating a physiologic role for CTR1 in the delivery of copper to the cytosol. A copper-dependent reporter gene construct, CUP1-lacZ, is not expressed in CTR1 mutants to the same level as in wild-type strains, and Cu,Zn superoxide dismutase activity is deficient in these mutants. The growth arrest that occurs in CTR1 mutants grown aerobically in copper-deficient media is attributable to the defect in Cu,Zn superoxide dismutase activity.

Aerobiosis↗

PubMed1989

Variations in the intralobular distribution of copper in the livers of copper-loaded rats in relation to the pathogenesis of copper storage diseases.

There are differences in the hepatic intralobular distribution of copper in copper storage related diseases which may be of pathogenetic significance. Male rats fed a high copper diet (1500 ppm) for 16 weeks were killed at intervals in an attempt to compare copper distribution in their livers with those in human, canine and ovine copper toxicosis. Copper was found to accumulate almost exclusively in the periportal and mid-zones of the rat liver lobules and was associated with progressive pathological changes which included focal and periportal degeneration and necrosis. This pattern of copper distribution contrasts markedly with the centrilobular retention reported in familial canine copper toxicosis and chronic copper poisoning in sheep which suggests that, in these conditions, a secretory deficiency may be less important than a metabolic zonal defect of intracellular copper metabolism. The pathological changes observed in copper-loaded rats have a different micro-anatomical localization from those in dogs and sheep, but show similarities to the early changes reported in the latter species and indicate the possibility of a similar cellular lesion.

Animals↗

PubMed2003

A redox switch in CopC: an intriguing copper trafficking protein that binds copper(I) and copper(II) at different sites.

The protein CopC from Pseudomonas syringae has been found capable of binding copper(I) and copper(II) at two different sites, occupied either one at a time or simultaneously. The protein, consisting of 102 amino acids, is known to bind copper(II) in a position that is now found consistent with a coordination arrangement including His-1, Glu-27, Asp-89, and His-91. A full solution structure analysis is reported here for Cu(I)-CopC. The copper(I) site is constituted by His-48 and three of the four Met residues (40, 43, 46, 51), which are clustered in a Met-rich region. Both copper binding sites have been characterized through extended x-ray absorption fine structure studies. They represent novel coordination environments for copper in proteins. The two sites are approximately 30 A far apart and have little affinity for the ion in the other oxidation state. Oxidation of Cu(I)-CopC or reduction of Cu(II)-CopC causes migration of copper from one site to the other. This behavior is observed both in NMR and EXAFS studies and indicates that CopC can exchange copper between two sites activated by a redox switch. CopC resides in the periplasm of Gram-negative bacteria where there is a multicopper oxidase, CopA, which may modulate the redox state of copper. CopC and CopA are coded in the same operon, responsible for copper resistance. These peculiar and novel properties of CopC are discussed with respect to their relevance for copper homeostasis.

Amino Acid Sequence↗

PubMed2006

Effects of copper sulfate and copper nitrate in aquatic medium on the restoration potential and accumulation of copper in stem cuttings of the terrestrial medicinal plant, Portulaca oleracea linn.

The stem cuttings of the terrestrial, ornamental plant, Portulaca oleracea, grew well in distilled water by producing adventitious roots and leaves. However, when exposed to various concentrations of sulfate and nitrate salts of copper resulted in a suppression of root growth, increase in initiation time of roots and sprouts and decay of stem cuttings from the cut open end, decrease in number of leaves with an increase in concentration of copper in the growth medium. Accumulation of copper increased with increasing concentrations of both copper sulfate and copper nitrate. However, copper accumulation was greater in copper nitrate than in copper sulfate treatment. Hence, copper in the presence of nitrate is more toxic than in the presence of sulfate. The accumulation factors in all treatment concentrations were greater than 1, hence P. oleracea is a copper accumulator.

Copper↗

PubMed1983

Enzyme-bound copper of dopamine beta-monooxygenase. Activation of the holoenzyme by added copper and uncoupling of electron transfer from hydroxylation by copper salicylate.

preparations of dopamine beta-monooxygenase containing a full complement of copper (4.2 copper atoms per tetramer) show increased ascorbate-supported catalytic activities after addition of an excess of copper ions. The significance of this observation on the question of the number of copper atoms per active site is discussed. Low molecular weight copper complexes such as copper salicylate cause uncoupling of electron transport from hydroxylation. This uncoupling is probably the reason for the well-known inhibition of this enzyme observed at high copper concentration. The onset of inhibition by the copper chelator bathocuproine disulfonate occurs on a faster time scale than the removal of enzyme-bound copper. Nevertheless, the copper removal is sufficiently rapid to require that it be considered in interpretation of inhibition experiments with chelators.

Adrenal Medulla↗

PubMed1994

Thiotungstate-copper interactions II. The effects of tetrathiotungstate on systemic copper metabolism in normal and copper-treated rats.

The intraperitoneal administration of tetrathiotungstate to rats (6-17.4 mg W/Kg BW) caused profound changes in copper metabolism in both normal rats and in rats pretreated with copper. Plasma copper associated with albumin increased, liver copper, particularly cytosol copper, was depleted, and biliary excretion was increased. There was also a movement of copper to higher molecular weight proteins in both liver cytosol and bile. In contrast to penicillamine, tetrathiotungstate did not increase liver cytosolic apometallothionein levels and reduced the rise provoked by copper. Metallothionein-bound copper was removed. Ceruloplasmin oxidase activity was inhibited and there was evidence for increased movement of copper into subcellular organelles, probably lysosomes. It is concluded that tetrathiotungstate has a genuine "decoppering" effect and could be considered as an alternative to thiomolybdates in the treatment of copper storage diseases.

Animals↗

PubMed1977

The binding of copper ions to copper-free bovine superoxide dismutase. Copper distribution in protein samples recombined with less than stoicheiometric copper ion/protein ratios.

Samples of superoxide dismutase containing less than stoicheiometric amounts of Cu2+ were obtained by either partial re-addition of Cu2+ to the Cu2+-free protein or partial removal of Cu2+ by controlled CN-treatment. In these samples the distribution of the metal between the two identical sites on the two subunits was studied by quantitative gel electrophoresis and found to be statistical only in the process of copper removal by CN-. In the other case the distribution fits a model of co-operative interaction between the two sites, where the sites are equivalent for the binding of the first Cu2+ ion, but the occupation of the first site lowers the activation energy of the binding of the second Cu2+ ion. This indicates that binding of Cu2+ ion at its site on one subunit brings about conformational changes that facilitate Cu2+ binding on the other subunit. These results may relate to possible intersubunit interactions during the catalytic activity.

Animals↗

PubMed1981

[Effect of copper status on reproductive performance and milk yield of female cattle in two copper deficient habitats. Effect of supplemental copper feeding on copper status].

The influence of a nutrition poor in Cu on the copper status of dairy cows was investigated with and without Cu-supplementation through the mineral mixture typical of the territory and enriched with Cu. The roughage produced in the territory investigated contained less than 8.0 mg Cu/kg and did not guarantee a Cu supply of the dairy cows meeting their needs. Feeding the mineral mixture rich in Cu improved the Cu-status of the dairy cows, did, however, in one of the territories not result in a Cu-incorporation in the liver that meets the needs. Possibly the reason for this divergent behaviour is an oversufficient S- and Fe-supply. In contrast to this, the Cu-content of the cerebrum of the cows in both territories showed the effect of the Cu in the mineral mixture.

Animal Feed↗

PubMed1991

Direct measurement of intramolecular electron transfer between type I and type III copper centers in the multi-copper enzyme ascorbate oxidase and its type II copper-depleted and cyanide-inhibited forms.

Transient kinetics of reduction of zucchini squash ascorbate oxidase (AO) by lumiflavin semiquinone have been studied by using laser flash photolysis. Second-order kinetics were obtained for reduction of the type I copper with a rate constant of 2.7 X 10(7) M-1 s-1, which is comparable to that obtained with other blue copper proteins such as plastocyanin. Following reduction, the type I copper was reoxidized in a protein concentration independent (i.e., intramolecular) reaction (kobs = 160 s-1). Comparison with literature values for limiting rate constants in transient single-turnover kinetic experiments suggests that intramolecular electron transfer probably is the rate-limiting step in enzyme catalysis. The extent of reoxidation of type I copper was approximately 55%, which is consistent with the approximately equal redox potentials of the type I and type III copper centers. Neither azide nor fluoride caused any significant changes in kinetics, although they are enzyme inhibitors and are thought to bind to the type II copper. In contrast, cyanide caused a concentration-dependent decrease in the extent of intramolecular electron transfer (with no change in rate constant), and decreased the rate constant for reduction of the type I copper by a factor of 2. The apparent dissociation constant for cyanide (0.2-0.4 mM) is similar to that reported for inhibition of enzyme activity. Removal of the type II copper from AO only marginally affected the kinetics of electron transfer to type I copper (k = 3.2 x 10(7) M-1 s-1) and slightly increased the extent but did not alter the rate constant of intramolecular electron transfer.(ABSTRACT TRUNCATED AT 250 WORDS)

Ascorbate Oxidase↗

PubMed1991

The SOD like activity of copper:carnosine, copper:anserine and copper:homocarnosine complexes.

Carnosine, anserine and homocarnosine are natural compounds which are present in high concentrations (2-20 mM) in skeletal muscles and brain of many vertebrates. We have demonstrated in a previous work that these compounds can act as antioxidants, a result of their ability to scavenge peroxyl radicals, singlet oxygen and hydroxyl radicals. Carnosine and its analogues have been shown to be efficient chelating agents for copper and other transition metals. Since human skeletal muscle contains one-third of the total copper in the body (20-47 mmol/kg) and the concentration of carnosine in this tissue is relatively high, the complex of carnosine:copper may be of biological importance. We have studied the ability of the copper:carnosine (and other carnosine derivatives) complexes to act as superoxide dismutase. The results indicate that the complex of copper:carnosine can dismute superoxide radicals released by neutrophils treated with PMA in an analogous mechanism to other amino acids and copper complexes. Copper:anserine failed to dismute superoxide radicals and copper:homocarnosine complex was efficient when the cells were treated with PMA or with histone-opsonized streptococci and cytochalasine B. The possible role of these compounds to act as physiological antioxidants that possess superoxide dismutase activity is discussed.

Anserine↗

PubMedDate not supplied

Nutritional copper deficiency in severely handicapped patients on a low copper enteral diet for a prolonged period: estimation of the required dose of dietary copper.

Six cases of nutritional copper deficiency were identified in a nursery institute for severely handicapped patients. All had been on prolonged enteral feeding of a copper-deficient diet and all had abnormalities related to the copper deficiency. Two of them had leukopenia, with or without macrocytic and normochromic anemia. After the oral administration of copper, the clinical and laboratory observations including neutrophil counts and serum copper and ceruloplasmin levels showed a complete recovery. The dietary copper requirement was estimated to be approximately 20 micrograms/kg/day for these patients, based on the correlation between the dietary copper intake and the levels of copper in the serum.

Adolescent↗

PubMed1985

Effects of castration and maturational age of male rats on the process of copper-stimulated release of luteinizing hormone releasing hormone from median eminence explants: evidence that androgens increase the affinity of the copper-interactive sites for copper.

We have previously shown that chelated copper stimulates the release of luteinizing hormone releasing hormone (LHRH) from explants of the median eminence area (MEA) incubated under in vitro conditions and that this stimulation involves a ligand-specific interaction. In this study, we addressed the question: do testicular steroids regulate the secretory response of LHRH neurons to copper? MEA, obtained from immature, mature, immature castrated and sham-operated rats, were incubated in the presence of various concentrations of copper for 15 min and then in the absence of copper for an additional period of 30 min. We noted that after a lag period of 5 min of incubation, the rate of LHRH release increased in a linear fashion for a period of 15 min. In addition, the rate of LHRH release as well as the rate at which LHRH release was accelerated were saturable functions of the concentration of copper. When incubation was carried out in the presence of a nonsaturating concentration of copper (50 microM), the fractional amount (percent of the total MEA content) of LHRH released from the MEA of castrated rats was significantly (p less than 0.001) lower than that from sham-operated rats; stimulated release being 0.9% and 1.4%, respectively. Similarly, copper-stimulated release from the MEA of immature rats was lower than that from the MEA of mature rats. However, when incubation was carried out in the presence of saturating concentrations of copper (100 or 200 microM), the percentage of stimulated release from the MEA of castrated rats was similar to that of sham-operated rats and significantly lower than that of mature and sham-operated rats, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed2001

Iatrogenic copper deficiency associated with long-term copper chelation for treatment of copper storage disease in a Bedlington Terrier.

A 9-year-old Bedlington Terrier was evaluated because of weight loss, inappetence, and hematemesis. Copper storage disease had been diagnosed previously on the basis of high hepatic copper concentration. Treatment had included dietary copper restriction and administration of trientine for chelation of copper. A CBC revealed microcytic hypochromic anemia. High serum activities of liver enzymes, high bile acid concentrations, and low BUN and albumin concentrations were detected. Vomiting resolved temporarily with treatment, but the clinicopathologic abnormalities persisted. Results of transcolonic portal scintigraphy suggested an abnormal shunt fraction. Results of liver biopsy and copper quantification revealed glycogen accumulation and extremely low hepatic copper concentration. Serum and hair copper concentrations were also low. Chelation and dietary copper restriction were tapered and discontinued. Clinical signs and all clinicopathologic abnormalities improved during a period of several months.

Animals↗

PubMed1997

Magnetic Interactions in the Copper Complex (L-Aspartato)(1,10-phenanthroline)copper(II) Hydrate. An Exchange-Coupled Extended System with Two Dissimilar Copper Ions.

We report EPR measurements in single-crystal samples at the microwave frequencies 9.8 and 34.3 GHz and magnetic susceptibility measurements in polycrystalline samples for the ternary complex of copper with aspartic acid and phenanthroline, (L-aspartato)(1,10-phenanthroline)copper(II) hydrate. The crystal lattice of this compound is composed of two dissimilar copper ions identified as Cu(A) and Cu(B), which are in two types of copper chains called A and B, respectively, running parallel to the b crystal axis. The copper ions in the A chains are connected by the aspartic acid molecule, and those in the B chains by a chemical path that involves a carboxylate bridge and a hydrogen bond. Both chains are held together by a complex network of hydrogen bonds and by hydrophobic interactions between aromatic amines. Magnetic susceptibility data indicate a Curie-Weiss behavior in the studied temperature range (2-300 K). The EPR spectra at 9.8 GHz display a single exchange collapsed resonance for any magnetic field orientation, in the so-called strong exchange regime. Those at 34.3 GHz are within the so-called weak exchange regime and display two resonances which belong to each type of copper ion chain. The decoupling of the spectra at 34.3 GHz using a theory based on Anderson's model for the case of two weakly exchange coupled spins S = (1)/(2) allows one to obtain the angular variation of the squares of the g-factor and the peak-to-peak line width of each resonance. This model also allows one to evaluate the exchange parameter |J(AB)/k| = 2.7(6) mK associated with the chemical path connecting dissimilar copper ions. The line width data obtained for each component of the spectra at 34.3 GHz are analyzed in terms of a model based on Kubo and Tomita's theory, to obtain the exchange parameters |J(A)/k| = 0.77(2) K and |J(B)/k| = 1.44(2) K associated with the chemical paths connecting the similar copper ions of types A and B, respectively.

Journal Article↗

PubMed1992

Assessment of liver copper status in cattle from plasma copper and plasma copper enzymes.

Copper status determined by liver biopsy was also assessed by 3 plasma parameters: total plasma copper (Cu) as well as ceruloplasmin (Cp) and amine oxidase E.C.1.4.3.6. (AO) activities. While 14 out of the 98 cattle, all kept in field conditions, had liver copper levels of less than 20 mg/kg only 5 of these could be distinguished by low plasma Cu and 3 by low Cp activity. In addition, some animals with apparently adequate liver copper had relatively low plasma Cu values, ca 0.5-0.6 mg/l. None of the cattle had decreased AO activity. When all 3 plasma parameters were combined in the form [AO] divided by ([Cp] x [Cu]), detection of the low liver copper was improved in that 9 out of 14 could be distinguished, whereas animals with more than 20 mg/kg DM liver Cu could not. It is suggested that this relationship, tentatively called an index, would merit examination in other situations, since it might provide a better guide to copper status and indicate whether copper repletion therapy was worthwhile.

Amine Oxidase (Copper-Containing)↗

PubMed2003

3[(dx2-y2,dxy)(pz)] excited state of binuclear copper(I) phosphine complexes: effect of copper-ligand and copper-copper interactions on excited state properties and photocatalytic reductions of the 4,4'-dimethyl-2,2'-bipyridinium ion in alcohols.

A comprehensive study of the structural and spectroscopic properties of two-, three-, and four-coordinate copper(I) complexes with aliphatic phosphine ligands is presented. All complexes described in this work are characterized by X-ray crystallography. The intramolecular Cu...Cu separations in [Cu2(dcpm)2]X2, [Cu2(dcpm)2-(CH3CN)2]X2, and [Cu2(dmpm)3]-(ClO4)2 (dcpm=bis(dicyclohexylphosphino)methane; dmpm=bis(dimethylphosphino)methane; X=ClO4- and PF6-) are in the range 2.639(2)-3.021(2) A. The anion...CuI interaction is weak, as evidenced by the nearest O...Cu separation of 2.558(6) A in [Cu2(dcpm)2](ClO4)2 and the closest Cu...F separation of 2.79(1) A in [Cu2(dcpm)2](PF6)2. The absorption bands of [Cu2(dcpm)2]X2 and [Cu2(dcpm)2(CH3CN)2]X2 (X=ClO4- and PF6-) at lambda max 307-311 nm in CH2Cl2 are assigned as 1[3d sigma* --> 4p sigma] transitions; this has been confirmed by resonance Raman spectroscopy. The triplet emissions in the visible region from these complexes exhibit long lifetimes and are sensitive to the environment. The lowest emissive excited state is tentatively ascribed as 3[(dx2-y2, dxy)(pz)] in nature. For [Cu2(dcpm)2]2+ salts in CH3CN, the emissive species is postulated to be [Cu2(dcpm)2(CH3CN)n]2+ (n > or = 3). Efficient photocatalytic reduction of MV2+ (4,4'-dimethyl-2,2'-bipyridinium) to MV+ in alcoholic solutions by using [Cu2(dcpm)2](PF6)2 or [Cu2(dppm)2(CH3CN)4](ClO4)2 (dppm=bis(diphenylphosphino)methane) as a catalyst has been observed. The addition of CH3CN or use of [Cu2(dmpm)3]-(ClO4)2 as a catalyst did not allow photocatalytic reduction processes to occur.

Journal Article↗

PubMed2001

Copper(I) complexes, copper(I)/O(2) reactivity, and copper(II) complex adducts, with a series of tetradentate tripyridylalkylamine tripodal ligands.

Copper(I) and copper(II) complexes possessing a series of related ligands with pyridyl-containing donors have been investigated. The ligands are tris(2-pyridylmethyl)amine (tmpa), bis[(2-pyridyl)methyl]-2-(2-pyridyl)ethylamine (pmea), bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine (pmap), and tris[2-(2-pyridyl)ethyl]amine (tepa). The crystal structures of the protonated ligand H(tepa)ClO(4), the copper(I) complexes [Cu(pmea)]PF(6) (1b-PF(6)), [Cu(pmap)]PF(6) (1c-PF(6)), and copper(II) complexes [Cu(pmea)Cl]ClO(4).H(2)O (2b-ClO(4).H(2)O), [Cu(pmap)Cl]ClO(4).H(2)O (2c-ClO(4).H(2)O), [Cu(pmap)Cl]ClO(4) (2c-ClO(4)), and [Cu(pmea)F](2)(PF(6))(2) (3b-PF(6)) were determined. Crystal data: H(tepa)ClO(4), formula C(21)H(25)ClN(4)O(4), triclinic space group P1, Z = 2, a = 10.386(2) A, b = 10.723(2) A, c = 11.663(2) A, alpha = 108.77(3) degrees, beta = 113.81(3) degrees, gamma = 90.39(3) degrees; 1b-PF(6), formula C(19)H(20)CuF(6)N(4)P, orthorhombic space group Pbca, Z = 8, a = 14.413(3) A, b = 16.043(3) A, c = 18.288(4) A, alpha = beta = gamma = 90 degrees; (1c-PF(6)), formula C(20)H(22)CuF(6)N(4)P, orthorhombic space group Pbca, Z = 8, a = 13.306(3) A, b = 16.936(3) A, c = 19.163(4) A, alpha = beta = gamma = 90 degrees; 2b-ClO(4).H(2)O, formula C(19)H(22)Cl(2)CuN(4)O(5), triclinic space group P1, Z = 4, a = 11.967(2) A, b = 12.445(3) A, c = 15.668(3) A, alpha = 84.65(3) degrees, beta = 68.57(3) degrees, gamma = 87.33(3) degrees; 2c-ClO(4).H(2)O, formula C(20)H(24)Cl(2)CuN(4)O(5), monoclinic space group P2(1)/c, Z = 4, a = 11.2927(5) A, b = 13.2389(4) A, c = 15.0939(8) A, alpha = gamma = 90 degrees, beta = 97.397(2) degrees; 2c-ClO(4), formula C(20)H(22)Cl(2)CuN(4)O(4), monoclinic space group P2(1)/c, Z = 4, a = 8.7682(4) A, b = 18.4968(10) A, c = 13.2575(8) A, alpha = gamma = 90 degrees, beta = 94.219(4) degrees; 3b-PF(6), formula [C(19)H(20)CuF(7)N(4)P](2), monoclinic space group P2(1)/n, Z = 2, a = 11.620(5) A, b = 12.752(5) A, c = 15.424(6) A, alpha = gamma = 90 degrees, beta = 109.56(3) degrees. The oxidation of the copper(I) complexes with dioxygen was studied. [Cu(tmpa)(CH(3)CN)](+) (1a) reacts with dioxygen to form a dinuclear peroxo complex that is stable at low temperatures. In contrast, only a very labile peroxo complex was observed spectroscopically when 1b was reacted with dioxygen at low temperatures using stopped-flow kinetic techniques. No dioxygen adduct was detected spectroscopically during the oxidation of 1c, and 1d was found to be unreactive toward dioxygen. Reaction of dioxygen with 1a-PF(6), 1b-PF(6), and 1c-PF(6) at ambient temperatures leads to fluoride-bridged dinuclear copper(II) complexes as products. All copper(II) complexes were characterized by UV-vis, EPR, and electrochemical measurements. The results manifest the dramatic effects of ligand variations and particularly chelate ring size on structure and reactivity.

Chelating Agents↗

PubMed1979

The enzyme-bound copper of dopamine beta-monooxygenase. Reaction with copper chelators, preparation of the apoprotein, and kinetics of the reconstitution by added copper.

The enzyme-bound copper of dopamine beta-monooxygenase reacted rapidly with the chelator bathocuproine disulfonate; the reaction in the presence of ascorbate was completed in 2 min at 25 degrees C with 1mM chelator. This reaction and also the reaction with EDTA could be used to prepare the apoenzyme, which in both cases was completely reactivated in less than 10 s. The reactivation data gave apparent Michaelis constants for copper 0.03 -- 0.2 micron. Trace amounts of copper in buffers and assay mixtures gave significant reactivation without added copper, unless they had been treated with a chelating resin. Titrations using the different chelation rates of free and enzyme-bound copper indicated that four copper atoms are bound per enzyme molecule of four subunits. The native enzyme was more stable against thermal inactivation than the apoenzyme, but this stability was only partially restored by addition of copper to the apoenzyme.

Adrenal Medulla↗