Studies on the metabolism of rat liver copper-metallothionein.
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ABSTRACT:
SUBMITTER: Mehra RK
PROVIDER: S-EPMC1144920 | biostudies-other | 1985 May
REPOSITORIES: biostudies-other
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Project description:When Neurospora crassa is grown in the presence of Cu(II) ions, it accumulates the metal with the concomitant synthesis of a low molecular weight copper-binding protein. The molecule binds 6 g-atom of copper per mole protein (Mr = 2200) and shows a striking sequence homology to the zinc- and cadmium-binding vertebrate metallothioneins. Absorption, circular dichroism, and electron paramagnetic resonance spectroscopy of Neurospora metallothionein indicate the copper to be bound to cysteinyl residues as a Cu(I)-thiolate complex of the polymeric mu-thiolate structure [Cu(I)6RS7]-. This metal-binding mode is also in agreement with the unusual luminescence of the protein. Spectral perturbation studies with HgCl2 and p-(chloromercuri)benzoate suggest that the 6 Cu(I)ions are coordinated to the seven cysteinyl residues in the form of a single metal cluster. Neurospora apometallothionein is also capable of binding in vivo group IIB metal ions [Zn(II), Cd(II), and Hg(II)] as well as paramagnetic Co(II) ions with an overall metal-to-protein stoichiometry of 3. The spectroscopic properties of the fully substituted forms are indicative of a distorted tetrahedral coordination. However, metal titration of the apoprotein shows the third metal ion to be differently coordinated than the other two metal ions. This difference can be explained by the presence of only seven cysteine residues in Neurospora metallothionein as opposed to nine cysteine residues in the three-metal cluster of the mammalian metallothioneins.
| S-EPMC1474700 | biostudies-literature
Project description:The kinetics of the increase of metallothionein mRNA in rat liver and kidney after CuCl2 injection was determined by cell-free translation and dot-blot hybridization of total RNA isolated at various times after the injection. Both assay procedures gave essentially the same result: a 16-fold increase in hepatic metallothionein mRNA was observed 7h after CuCl2 injection, with a decline to basal values by 15 h. The response in the kidney was less dramatic, with a 6-fold increase in metallothionein mRNA 5 h after injection, and basal values were attained by 12h. The rise in Cu2+ concentration in both organs was closely correlated with the increase in metallothionein mRNA; hepatic Cu2+ was increased 5.9-fold by 5h after injection and renal Cu2+ was increased 4.3-fold 5h after injection. The Zn2+ concentration in the liver had not risen significantly within 5h of Cu2+ injection. Renal Zn2+ concentrations did not alter appreciably in the Cu2+-treated animals. These results support the conclusion that Cu2+ is acting as a primary inducer of metallothionein mRNA in the rat.
| S-EPMC1145000 | biostudies-other
Project description:BackgroundA major pathological hallmark of AD is the deposition of insoluble extracellular beta-amyloid (Abeta) plaques. There are compelling data suggesting that Abeta aggregation is catalysed by reaction with the metals zinc and copper.Methodology/principal findingsWe now report that the major human-expressed metallothionein (MT) subtype, MT-2A, is capable of preventing the in vitro copper-mediated aggregation of Abeta1-40 and Abeta1-42. This action of MT-2A appears to involve a metal-swap between Zn7MT-2A and Cu(II)-Abeta, since neither Cu10MT-2A or carboxymethylated MT-2A blocked Cu(II)-Abeta aggregation. Furthermore, Zn7MT-2A blocked Cu(II)-Abeta induced changes in ionic homeostasis and subsequent neurotoxicity of cultured cortical neurons.Conclusions/significanceThese results indicate that MTs of the type represented by MT-2A are capable of protecting against Abeta aggregation and toxicity. Given the recent interest in metal-chelation therapies for AD that remove metal from Abeta leaving a metal-free Abeta that can readily bind metals again, we believe that MT-2A might represent a different therapeutic approach as the metal exchange between MT and Abeta leaves the Abeta in a Zn-bound, relatively inert form.
| S-EPMC2920313 | biostudies-literature
Project description:Soluble fractions from chick liver and aorta were examined for copper-binding proteins. In liver a zinc-binding thionein appeared to be the major binding protein for copper. Aortic tissue contained only traces of this thionein protein. Unlike liver, moderate amounts of soluble copper in aorta showed no association with macromolecules. Chicks fed on copper-deficient diets for 8 days had one-third the liver copper concentrations of controls. Aortic copper concentration was decreased only slightly, but the activity of lysyl oxidase, a copper-dependent enzyme in aorta, was decreased significantly. Treating the deficient chicks with CuSO4 (1 mg/kg) restored liver copper rapidly. The increase correlated with the binding of copper to a 10 000-mol.wt. component in the soluble fraction. Aortic copper concentrations responded much less to the CuSO4 treatment, but lysyl oxidase activity was again measurable in the tissue. Radioactive isotopes of copper bound almost exclusively to the 10 000-mol.wt. component in liver and to components of mol.wt. 30 000 or above in aorta. Hardly any of the administered radioactivity appeared with the 10 000-mol.wt. components in aorta, and none was found with unbound copper. The 30 000-mol.wt. components in aorta showed superoxide dismutase activity that was sensitive to NaCN. They also showed the highest specific activity of copper of any other aorta component. A clear distinction was seen between the metabolism of copper in liver and aortic tissues. Whereas a copper thionein, metallothionein, was a major component in the liver pathway, it is doubtful that this protein plays a major role in the intracellular metabolism of copper in aortic tissue.
| S-EPMC1158383 | biostudies-other
Project description:The luminescence lifetime of Cu-metallothionein from the fungus Neurospora crassa has been studied by the frequency-domain emission technique. Lifetimes of 10.3 and 3.4 microseconds have been found for the protein in the absence and in the presence of oxygen respectively. Binding of Hg(II) results in a quenching of the luminescence correlated to the shortening of lifetime to 0.3-0.4 microsecond. No quenching by oxygen is found for the Hg(II)-Cu-metallothionein adduct. By analogy to model compounds, luminescence emission is attributed to a triplet excited state of a Cu(I)-to-sulphur charge-transfer complex. The comparison of bimolecular quenching constants for O2 and acrylamide indicates a highly compact structure of the protein.
| S-EPMC1138644 | biostudies-other
Project description:A screen of a genomic library from Mycobacterium tuberculosis (Mtb) identified a small, unannotated open reading frame (MT0196) that encodes a 4.9-kDa, cysteine-rich protein. Despite extensive nucleotide divergence, the amino acid sequence is highly conserved among mycobacteria that are pathogenic in vertebrate hosts. We synthesized the protein and found that it preferentially binds up to six Cu(I) ions in a solvent-shielded core. Copper, cadmium and compounds that generate nitric oxide or superoxide induced the gene's expression in Mtb up to 1,000-fold above normal expression. The native protein bound copper within Mtb and partially protected Mtb from copper toxicity. We propose that the product of the MT0196 gene be named mycobacterial metallothionein (MymT). To our knowledge, MymT is the first metallothionein of a Gram-positive bacterium with a demonstrated function.
| S-EPMC2749609 | biostudies-literature
Project description:We describe a novel metallothionein gene from Tetrahymena thermophila that has a strong copper-inducible promoter. This promoter can be turned on and off rapidly, making it a useful system for induction of ectopic gene expression in Tetrahymena and enhancing its applications in cell and molecular biology, as well as biotechnology.
| S-EPMC1405887 | biostudies-literature
Project description:Large amounts of Cu-metallothionein were obtained by 2-mercaptoethanol and sodium dodecyl sulphate extractions of the particulate fractions of the liver of pigs given high-Cu2+ diets or rats injected with Cu2+. Three isoproteins were purified from pig liver and characterized on the basis of their physicochemical properties, metal content and amino acid composition. No such pool of Cu-metallothionein was present in the liver of Cu2+-loaded sheep or of rats given Cu2+-supplemented diets.
| S-EPMC1153511 | biostudies-other
Project description:AimThe current study was designed to evaluate the potential hepatoprotective and immunomodulatory effects of copper-nicotinate complex (CNC) against methionine- and choline-deficient diet (MCDD)-induced fatty liver in rats.Materials and methodsForty male Wistar rats were randomly allocated into one of four equal-sized groups (G1-G4). The G1 group was fed a balanced diet and kept under normal conditions; the G2 group received CNC orally at a dose of 0.043 mg/kg body weight, 3 times/week for 4 weeks, and a balanced diet; the G3 group was fed an MCDD for 4 weeks; and the G4 group was fed an MCDD and administered CNC at the same dose and route as G2. Blood samples were collected for the determination of serum enzyme activity. After 4 weeks of treatment, liver specimens were collected for the evaluation of the oxidative/antioxidative markers, cytokine gene expression, and histopathological examination.ResultsCNC improved MCDD-induced liver dysfunctions by recovering serum alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transferase activities to their normal levels. The glutathione (GSH) level and superoxide dismutase (SOD) activity significantly decreased, while lipid peroxidation (as reflected by malondialdehyde [MDA]) markedly increased in the liver tissue of the MCDD group. After cotreatment with MCDD and CNC, the GSH level and SOD activity markedly increased and the MDA level significantly decreased to return to normal levels. After cotreatment with MCDD and CNC, significant downregulation of the mRNA expression of hepatic interleukin (IL)-1β, IL-4, macrophage inflammatory protein-1α, and monocyte chemoattractant protein-1 genes was found. Moreover, CNC reduced fatty liver complications by reducing the number of hepatic vacuolations, degenerative changes in the hepatocytes, and hemorrhage.ConclusionCNC has the potential to limit tissue injury and possibly prevent the progression to severe liver disease caused by an MCDD.
| S-EPMC6989322 | biostudies-literature
Project description:BackgroundCopper (Cu) and zinc (Zn) are essential nutrients and cofactors of enzymatic reactions with their binding partner. Metallothionein (MT) plays an important role in protecting against heavy metals and oxidative injury, however it may also portend drug resistance and a worse prognosis for hepatocellular carcinoma (HCC) patients. The aim of this study was to determine the amount of Cu, Zn, Cu/Zn and MT in evaluating a group of patients with HCC, including those treated with lenvatinib.MethodsWe enrolled 175 patients with HCC (139 men, 36 women; mean age 71.1 years; hepatitis C virus n = 85, hepatitis B virus n = 19, hepatitis C virus and hepatitis B virus n = 2, non-alcoholic steatohepatitis n = 39, alcohol n = 25, others n = 5; Child-Pugh A n = 141, Child-Pugh B n = 30, Child-Pugh C n = 4; Barcelona clinic liver cancer (BCLC) stage 0 n = 38, stage A n = 56, stage B n = 39, stage C n = 38, stage D n = 4). We evaluated the associations between Cu, Zn and MT. The study outcome was liver cancer-specific survival. Moreover, we treated 12 HCC patients with lenvatinib and investigated the changes in MT during lenvatinib therapy.ResultsThe serum level of Cu was positively correlated with alanine aminotransferase and the BCLC stage. The serum level of Zn decreased concordant with liver disease progression. Patients with a Cu/Zn ratio≥0.999 had significantly improved rates of survival when compared to patients with a Cu/Zn ratio<0.999 (45.3 vs. 30.1 months, p<0.001). MT was significantly correlated with the Cu/Zn ratio and increased after the administration of lenvatinib. Using multivariate Cox regression analyses, it was determined that the Cu/Zn ratio (hazard ratio [HR]: 1.442, p = 0.008), alpha-fetoprotein (HR: 1.000, p<0.001) and BCLC stage (HR: 2.087, p<0.001) were independent predictors of survival.ConclusionsThe Cu/Zn ratio could serve as a useful predictive marker for survival in cases of HCC. MT levels increased in HCC patients receiving lenvatinib therapy, and maybe a predictor of reduced survival.
| S-EPMC7455040 | biostudies-literature