SEARCH · Search PubMed

Results for “THIONEINE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources

PubMed1979

Cell-free synthesis of rat liver zinc-thioneins.

The induction of rat liver zinc-thioneins mRNA was studied in a wheat germ cell-free translation system. Liver poly A rich polysomal RNA was isolated from rats which had been injected with zinc sulfate 5 h previously. These RNA preparations stimulated the incorporation of [35S]cystine into trichloroacetic acid insoluble proteins when assayed in the cell-free synthetic system. The translation products were characterized by Sephadex G-75 chromatography in 8 M urea--50 mM beta-mercaptoethanol, by disc gel electrophoresis in 4 M area--Tris-glycine buffer (pH 9.2), and by peptide fingerprinting with pepsin. These results were identical with authentic rat liver zinc-thioneins. The zinc-thioneins mRNA activity in the control rats, however, was minimal. The stimulation in zinc-thioneins synthesis observed in the cell-free synthesis was similar to the increased synthesis of these polypeptides in vivo.

Amino Acids↗

PubMedDate not supplied

Application of covalent affinity chromatography with thiol-disulphide interchange for determination of environmental exposure to heavy metals based on the quantitative isolation of Cd-thionein from human breast milk.

The aim of this study was to test a new chromatographic method for the quantitative determination of Cd-thionein (Cd-Th) in human breast milk, in order to determine the level of exposure to heavy metals. Cd-thionein was isolated by covalent affinity chromatography with thiol-disulphide interchange, which is a modern separation technique of high affinity, good repeatability and reproducibility, allowing specific isolation of the thiolproteins. The fundamentals of indirect determination of the contents of metallothionein protein from human milk were worked out through estimation of the quantities of cadmium bound with Cd-thionein and adsorbed on covalent affinity chromatography gel during a separation process.

Chromatography, Affinity↗

PubMedDate not supplied

Application of covalent affinity chromatography with thiol-disulphide interchange for determination of environmental exposition to heavy metals based on the quantitative determination of Zn-thionein from physiological human fluids by indirect method based on analysis of metal contents.

Intoxication with heavy metals results in numerous poisonings and diseases. They disturb metabolism of the system, are the source of cancer, degeneration changes and others. As a result of kidney damage the urine of people exposed to heavy metals contains different low molecular weight proteins, oligopeptides and amino acids, indicating pathological changes. One of the proteins is a very specific metallopolythiopolypeptide--metallothionein (MT). Based on earlier investigations, a very good correlations has been found between the contents of metallothionein in urine and plasma and the concentration of heavy metals in the blood, urine, kidneys, liver and brain and general in level of exposition to heavy metals. The aim of our investigations was to carry out quantitative isolation of Zn-thionein (Zn-Th), in order to determine the level of exposition to heavy metals. For Zn-Th protein isolation by covalent affinity chromatography with thiol-disulphide interchange (CAC-TDI) was applied, which is a modern technique of separation of a high affinity, good repeatability and reproducibility, allowing specific isolation of the thiol-proteins CAC-TDI gel was used as a solid-phase extraction (SPE) support for preconcentration of Zn-Th protein and Zn bonded with Zn-Th from water, rine, plasma and breast milk samples. The investigations showed unfavourable effect of the support on separation of thiol proteins and good correlation between the concentration of MTs protein added to water, plasma and urine and the concentration of protein indirectly determined via atomic absorption spectrometric (AAS) method, by preconcentration on SPE support metals formerly bound with MT protein and absorbed on CAC-TDI gel and calculated from metals concentration. The present paper is a continuation of earlier experiments on quantitation of Hg-thionein and Cd-thionein in physiological fluids and homogenates.

Chromatography, Affinity↗

PubMed1979

Oxidation-reduction reactions of copper-thiolate centres in Cu-thionein.

Cu-thionein from yeast was investigated by EPR spectroscopy to probe the oxidation state of copper, and the effects on it of oxidizing and reducing agents. At pH 0.2 the copper was released, but no EPR signal from Cu(II) was observed, unless air was present. Optical experiments did not detect any disulphide groups which might have been formed during anaerobic release of copper. The mercurial, p-hydroxymercuribenzoate caused the release of EPR-detectable copper only under aerobic conditions, and EDTA caused release of Cu(II) on heating. No reduction of the copper-thiolate units in Cu-thionein by ascorbate was detected. Potentiometric titrations with hexachloroiridate(IV) or hexacyanoferrate(III) produced several different Cu(II) EPR signals at various stages of oxidation. The former oxidizing agent required a lower oxidation-reduction potential (+350 mV) to oxidize the copper, than the latter (+410 mV) and neither titration was fully reversible. The EPR signal from Cu(II) oxidized by hexachloroiridate(IV) resembled that produced by p-hydroxy-mercuribenzoate in air, suggesting that the copper was released from its thiolate ligands. It is concluded that the EPR non-detectable copper in the native protein is Cu(I). Oxidation-reduction of the copper-thiolate clusters of Cu-thionein is proposed to be decisive for controlling storage and transport of cellular copper.

Biological Transport↗

PubMed1986

An immunological study of a Pb-thionein like protein in rat liver.

Administration of a sublethal dose of lead acetate to rats induced the simultaneous synthesis of a Pb-thionein like protein (Pb-BP) and Zn-thionein in the liver. To determine of the Pb-BP is a species of metallothionein, immunological properties of this protein were investigated. The results indicate that the Pb-BP is cross-reactive with the antibody against rat Zn-thionein II, strongly suggesting that the Pb-BP is a metallothionein.

Animals↗

PubMed1988

Differently bound copper(I) in yeast Cu8-thionein.

The reactivity of yeast Cu-thionein in the presence of the Cu(I)-chelators, bathocuproinesulphonate and cuproine, was examined to distinguish between possible differently coordinated Cu(I). Electronic absorption measurements revealed that two out of eight coppers of the protein reacted within seconds with the chelator. At the same time, the shape and magnitude of the characteristic Cotton bands attributable to the Cu(I)-thiolate chromophores remained constant. Due to the successful removal of circular dichroic silent copper, all specific theta Cu values rose by 53% of the original value. Thus, it is strongly suggested that two or more distinct types of Cu(I) ought to be present in Cu8-thionein. In the light of the many different Cu/cysteine ratios of Cu-thioneins from vertebrate and microbial origin, possible interconversion reactions of the Cu(I)-thiolate centres seem to be likely.

Carrier Proteins↗

PubMed1993

A pulse radiolytic study on the reaction of hydroxyl and superoxide radicals with yeast Cu(I)-thionein.

In a pulse radiolytic study employing aqueous intact yeast copper(I)-thionein at pH 7 it was shown that both superoxide and hydroxyl radicals efficiently react with this Cu(I)- and thiolate-rich protein. The reaction constant of hydroxyl radicals with Cu(I)-thionein was determined by competition kinetics and was 2.2 x 10(11) M-1 s-1 at a rate close to a diffusion-controlled limit. The reaction of Cu(I)-thionein with superoxide was also successful and proceeded at a rate of 7.5 x 10(6) M-1 s-1. According to chiroptical and luminescence emission measurements minor oxidation of the copper(I)-thiolate oligonuclear binding centres was observed, leading to the release of some Cu(II). It is important to realise the dual reactivity of this yeast Cu(I)-thiolate protein in controlling copper transport and storage as well as its distinct role in the scavenging of free radicals.

Binding Sites↗

PubMed2003

MTO: the second member of a Drosophila dual copper-thionein system.

Drosophila MTO metal binding features were analyzed for comparison with MTN, the paralogous Drosophila metallothionein, and to classify MTO as either zinc- or copper-thionein. This was achieved by a combination of in vivo, in vitro and in silico methodologies. All the results unambiguously classified MTO as a second Drosophila copper-thionein, putting Drosophila forward as the only metazoan in which any zinc-thionein has still to be reported. Interestingly, experimental data only showed minor differences in the coordinative behavior of both MTs, but provided a characteristic spectroscopic fingerprint, revealing the possible binding of chloride anions in certain metal-MTO aggregates.

Amino Acid Sequence↗

PubMed1981

Metal-dependent properties of metallothionein. Replacement in vitro of zinc in zinc-thionein with copper.

Metal-dependent changes in the properties of metallothionein were investigated in vitro by replacing Zn2+ in zinc-thionein with Cu+ and Cu2+. Metallothionein was separated into isoproteins on a gel-permeation column by elution with alkaline buffer solution, the separation being due to the dissociation of hydroxy groups in the gel material. The two metals in metallothioneins were detected simultaneously by introducing the eluate of the column, which was attached to a high-pressure liquid chromatograph, to two flame atomic-absorption spectrophotometers. Zn2+ in zinc-thionein was replaced with 1.5 and 1 mol. equiv. of Cu+ and Cu2+ respectively. The replacement with Cu2+ accompanied intramolecular oxidation of thiol groups in metallothioneins and the oxidized metallothioneins showed different chromatographic properties from the original ones, probably due to changes in the isoelectric points. The oxidized forms of metallothionein were reducible by mercaptoethanol. Reduction of Cu2+ to Cu+ followed by the replacement of Zn2+ in zinc-thionein with Cu+ occurred in the presence of glutathione.

Animals↗

PubMed1986

Copper transport from Cu(I)-thionein into apo-caeruloplasmin mediated by activated leucocytes.

A study on the transfer of copper from Cu-thionein into apo-caeruloplasmin, using Cu-thionein that was previously oxidised by activated leucocytes, was performed. Cu(I)-thiolate oxidation was conveniently monitored by the progressive decline of the specific Cotton bands between 400 and 300 nm. The characteristic e.p.r. properties and NN-dimethyl-p-phenylenediamine oxidase activity indicated a successful formation of caeruloplasmin. Taking into account the simultaneous occurrence of leucocytes, apo-caeruloplasmin and Cu-thionein in blood plasma, such an interaction would favour a possible metabolic link between either copper protein.

Animals↗

PubMed1991

Zinc transfer from transcription factor IIIA fingers to thionein clusters.

The rapid induction of thionein (apometallothionein) by many endogenous stimuli such as steroid hormones, cytokines, and second messengers suggests that this cysteine-rich, metal binding protein participates in an as yet undefined role in cellular regulatory processes. This study demonstrates with DNA and RNA binding assays and in vitro transcription measurements that thionein suppresses the binding of the Xenopus laevis zinc finger transcription factor IIIA (TFIIIA) to 5S RNA and to the 5S RNA gene and abrogates the capacity of TFIIIA to initiate the RNA polymerase III-catalyzed synthesis of 5S RNA. The effect is reversed by the addition of zinc and is not observed in the TFIIIA-independent transcription of a tRNA gene by the same RNA polymerase. In view of the strong tendency of thionein to complex posttransition metals such as zinc, one effect of its enhanced synthesis in vivo could be to reduce the intracellular disposability of zinc and thus modulate the actions of zinc-dependent enzymes and proteins, most notably those of the zinc finger transcription factors.

Animals↗

PubMed1998

Control of zinc transfer between thionein, metallothionein, and zinc proteins.

Metallothionein (MT), despite its high metal binding constant (KZn = 3.2 x 10(13) M-1 at pH 7.4), can transfer zinc to the apoforms of zinc enzymes that have inherently lower stability constants. To gain insight into this paradox, we have studied zinc transfer between zinc enzymes and MT. Zinc can be transferred in both directions-i.e., from the enzymes to thionein (the apoform of MT) and from MT to the apoenzymes. Agents that mediate or enhance zinc transfer have been identified that provide kinetic pathways in either direction. MT does not transfer all of its seven zinc atoms to an apoenzyme, but apparently contains at least one that is more prone to transfer than the others. Modification of thiol ligands in MT zinc clusters increases the total number of zinc ions released and, hence, the extent of transfer. Aside from disulfide reagents, we show that selenium compounds are potential cellular enhancers of zinc transfer from MT to apoenzymes. Zinc transfer from zinc enzymes to thionein, on the other hand, is mediated by zinc-chelating agents such as Tris buffer, citrate, or glutathione. Redox agents are asymmetrically involved in both directions of zinc transfer. For example, reduced glutathione mediates zinc transfer from enzymes to thionein, whereas glutathione disulfide oxidizes MT with enhanced release of zinc and transfer of zinc to apoenzymes. Therefore, the cellular redox state as well as the concentration of other biological chelating agents might well determine the direction of zinc transfer and ultimately affect zinc distribution.

Animals↗

PubMed1984

Oxidation of Cu(I)-thionein by enzymically generated H2O2.

Very little is known of the metabolism of copper on a molecular level. For example, there is no evidence of an oxidative breakdown of Cu(I)-thionein leading to Cu(II). Thus it was of interest to use L- and D-amino-acid oxidases, amino oxidase and galactose oxidase to control the oxidation of Cu(I)-thionein by enzymically generated H2O2. In the presence of these enzymes Cu(II) was generated in each case. In a more detailed study the Cu(I)-thiolate chromophores of Cu-thionein were oxidized in the presence of xanthine oxidase as deduced from spectrometrical measurements using EPR and circular dichroism. Unlike Cu2Zn2-superoxide dismutase catalase inhibited the oxidative cleavage, suggesting peroxide as the actual oxidizing agent. Possibly there is an enzymic oxidative pathway for the generation of biologically important Cu(II).

Animals↗

PubMed1984

[Purification and properties of copper thionein].

A novel procedure for purification of copper-thionein from rabbit liver was developed. The molecular mass, copper, and thiol contents were determined. The properties of the protein were compared with those of Cd-thionein. Copper was removed from Cu-thionein and the reconstitution was achieved. The binding of copper leads to an increase in absorbance at 260 nm.

Animals↗

PubMed1987

The involvement of catecholamines and polypeptide hormones in the multihormonal modulation of rat hepatic zinc thionein levels.

Catecholamines can induce rat hepatic zinc thionein to high levels via alpha 1- and beta 2-adrenoceptors. Polypeptide hormones (glucagon and angiotensin II) are also inducers, but only to the moderate levels attained by glucocorticoids (dexamethasone). Turpentine induced inflammation stimulates the synthesis of ZnMT, but this process is not mediated by catecholamines. Phorbol esters, which are tumor promoters, can stimulate protein kinase C. Angiotensin II and alpha 1-agonists activate protein kinase C via diacylglycerol release from phosphatidylinositol-4,5-diphosphate. Phorbol esters can also stimulate the synthesis of rat hepatic zinc thionein, implicating protein kinase C activation in this induction. The multihormonal modulation of metallothionein gene activation has become increasingly more complex.

Angiotensin II↗

PubMed1987

Hepatic lysosomal copper-thionein.

In certain pathological and experimental conditions associated with hepatic copper overload, an important portion of the excess metal is bound to a copper-thionein and sequestered in hepatocellular lysosomes. The localization can be demonstrated visually by using histochemical and immunocytochemical stains and by extraction of the Cu-protein from particulate fractions of liver homogenates. The livers of Bedlington terriers affected by an inherited defect resulting in the accumulation of large quantities of copper display hepatocellular lysosomes which appear as dense, insoluble, copper-rich granules. Purification and solubilization of the fraction containing these granules yields a copper-thionein with little zinc, which displays homology with other known metallothioneins. Although the primary genetic defect which underlies the pathogenesis of this form of hepatic copper overload is still unknown, circumstantial evidence suggests that sequestration of the protein by lysosomes may be temporarily cytoprotective.

Aging↗

PubMed1983

Effect of acute stresses on Zn-thionein production in rat liver.

Male Wistar strain rats were exposed to acute stress from broad-band noise [100 dB (A) for 1 h] or cold (4 degrees C for 24 h). Following exposure to noise for 1 h, serum and adrenal gland showed about 1.8 times and 2.5 times the corticosterone levels of the control group, but this enhancement was not observed after exposure to cole. Both stresses increased Zn-thionein significantly in the liver. Furthermore, the two stresses increased the content of Zn in the 30,000 g supernatant fraction of the liver, though serum Zn concentration was not altered. It is believed that thionein is a regulatory protein with a specific function for Zn metabolism in organs. Although it is known that corticosterone affects Zn metabolism in man and animals, there is little investigation of the effect of environmental stresses on Zn metabolism. The present data suggest that Zn metabolism may be important in the investigation of the effects of repeated and long term exposure to environmental stresses involving noise and cold.

Acute Disease↗

PubMed1989

Reconstitution of neurocupreins by Cu-thioneins.

Cu-thioneins isolated from liver and brains are able to transfer their copper atoms to apoforms of neurocuprein 1 and 2. At the same time, the apoform of Cu-thionein is unable to accept copper from holoforms of both neurocupreins.

Animals↗