Copper transport from Cu(I)-thionein into apo-caeruloplasmin mediated by activated leucocytes.
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ABSTRACT:
SUBMITTER: Schechinger T
PROVIDER: S-EPMC1147407 | biostudies-other | 1986 Nov
REPOSITORIES: biostudies-other
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Project description:The direct incorporation of Cu(I) from [Cu(I)(thiourea)3]Cl, a structural analogue of Cu-thionein, into apo-stellacyanin, was successful both aerobically and anaerobically. A characteristic c.d. band of Cu(I)-stellacyanin at 270 nm (0 = -12.5 X 10(3) degrees X cm2 X dmol-1) was seen. On oxidation with hexacyanoferrate(III) or by air, the correct Cu(II) binding into the active centre of this 'Type 1' Cu-protein was deduced from chiroptical measurements which were supported by e.p.r. data. Thus Cu-thiourea turned out to be an excellent Cu(I)-donor in aqueous systems for the complete reconstitution of mononuclear Blue copper proteins.
| S-EPMC1144127 | biostudies-other
Project description:Investigation of copper status can be a diagnostic challenge. The non-caeruloplasmin-bound copper (NCC) has deficiencies; accordingly, the copper:caeruloplasmin ratio has been suggested as an alternative index of copper status. A reference interval for this index was derived. In addition to making the interpretation of copper easier, the copper:caeruloplasmin ratio should also enable adjustment for relatively high caeruloplasmin concentrations without recourse to producing gender- and age-derived intervals. The copper:caeruloplasmin ratio has weaknesses similar to those identified for NCC in that immunological methods used for caeruloplasmin can cross react with apocaeruloplasmin and there is no standardised method for caeruloplasmin. Caeruloplasmin assays also have uncertainty from precision, bias and specificity and, accordingly, method-related differences may have a large effect on the copper:caeruloplasmin ratio in a manner similar to the NCC.
| S-EPMC2001115 | biostudies-other
Project description:We report here the crystal structure of yeast copper thionein (Cu-MT), determined at 1.44-A resolution. The Cu-MT structure shows the largest known oligonuclear Cu(I) thiolate cluster in biology, consisting of six trigonally and two digonally coordinated Cu(I) ions. This is at variance with the results from previous spectroscopic determinations, which were performed on MT samples containing seven rather than eight metal ions. The protein backbone has a random coil structure with the loops enfolding the copper cluster, which is located in a cleft where it is bound to 10 cysteine residues. The protein structure is somewhat different from that of Ag(7)-MT and similar, but not identical, to that of Cu(7)-MT. Besides the different structure of the metal cluster, the main differences lie in the cysteine topology and in the conformation of some portions of the backbone. The present structure suggests that Cu-MT, in addition to its role as a safe depository for copper ions in the cell, may play an active role in the delivery of copper to metal-free chaperones.
| S-EPMC544076 | biostudies-literature
Project description:Cu(+)-ATPases drive the efflux of Cu(+) from the cell cytoplasm. During their catalytic/transport cycle, cytoplasmic Cu(+)-chaperones deliver the metal to the two transmembrane metal-binding sites (TM-MBSs) responsible for Cu(+) translocation. Here, using Archaeoglobus fulgidus Cu(+)-ATPase CopA and the C-terminal Cu(+)-chaperone domain of CopZ (Ct-CopZ), we describe the mechanism of Cu(+) transfer to both TM-MBSs. In absence of other ligands, Ct-CopZ transfers Cu(+) to wild-type CopA and to various CopA constructs lacking or having mutated cytoplasmic metal-binding domains, in a fashion consistent with occupancy of a single TM-MBS. Similar experiments performed in the presence of 2.5 mm ADP-Mg(2+), stabilizing an E1.ADP, lead to full occupancy of both TM-MBSs. In both cases, the transfer is largely stoichiometric, i.e. equimolar amounts of Ct-CopZ.Cu(+) saturated the TM-MBSs. Experiments performed with CopA mutants lacking either TM-MBS showed that both sites are loaded independently, and nucleotide binding does not affect their availability. The nucleotide-induced E2-->E1 transition is structurally characterized by a large displacement of the A and N domains opening the cytoplasmic region of P-type ATPases. Then, it is apparent that, whereas the first Cu(+)-chaperone can bind an ATPase form available in the absence of ligands, the second requires the E1.nucleotide intermediary to interact and deliver the metal. Interestingly, independent of TM-MBS Cu(+) loading, nucleotide binding also prevents the regulatory interaction of the N-terminal cytoplasmic metal-binding domain with the nucleotide binding domain.
| S-EPMC2742845 | biostudies-literature
Project description:Among the different synthesis approaches to colloidal nanocrystals, a recently developed toolkit is represented by cation exchange reactions, where the use of template nanocrystals gives access to materials that would be hardly attainable via direct synthesis. Besides, postsynthetic treatments, such as thermally activated solid-state reactions, represent a further flourishing route to promote finely controlled cation exchange. Here, we report that, upon in situ heating in a transmission electron microscope, Cu2Se or Cu nanocrystals deposited on an amorphous solid substrate undergo partial loss of Cu atoms, which are then engaged in local cation exchange reactions with Cu "acceptor" phases represented by rod- and wire-shaped CdSe nanocrystals. This thermal treatment slowly transforms the initial CdSe nanocrystals into Cu(2-x)Se nanocrystals, through the complete sublimation of Cd and the partial sublimation of Se atoms. Both Cu "donor" and "acceptor" particles were not always in direct contact with each other; hence, the gradual transfer of Cu species from Cu2Se or metallic Cu to CdSe nanocrystals was mediated by the substrate and depended on the distance between the donor and acceptor nanostructures. Differently from what happens in the comparably faster cation exchange reactions performed in liquid solution, this study shows that slow cation exchange reactions can be performed at the solid state and helps to shed light on the intermediate steps involved in such reactions.
| S-EPMC4768288 | biostudies-literature
Project description:Regulation of cellular copper (Cu) homeostasis involves Cu-transporting ATPases (Cu-ATPases), i.e., ATP7A and ATP7B. The question as to how these Cu-ATPases in brain barrier systems transport Cu, i.e., toward brain parenchyma, cerebrospinal fluid (CSF), or blood, remained unanswered. This study was designed to characterize roles of Cu-ATPases in regulating Cu transport at the blood-brain barrier (BBB) and blood-CSF barrier (BCB) and to investigate how exposure to toxic manganese (Mn) altered the function of Cu-ATPases, thereby contributing to the etiology of Mn-induced parkinsonian disorder. Studies by quantitative real-time RT-PCR (qPCR), Western blot, and immunocytochemistry revealed that both Cu-ATPases expressed abundantly in BBB and BCB. Transport kinetic studies by in situ brain infusion and ventriculo-cisternal (VC) perfusion in Sprague Dawley rat suggested that the BBB was a major site for Cu entry into brain, whereas the BCB was a predominant route for Cu efflux from the CSF to blood. Confocal evidence showed that the presence of excess Cu or Mn in the choroid plexus cells led to ATP7A relocating toward the apical microvilli facing the CSF, but ATP7B toward the basolateral membrane facing blood. Mn exposure inhibited the production of both Cu-ATPases. Collectively, these data suggest that Cu is transported by the BBB from the blood to brain, which is mediated by ATP7A in brain capillary. By diffusion, Cu ions move from the interstitial fluid into the CSF, where they are taken up by the BCB. Within the choroidal epithelial cells, Cu ions are transported by ATP7B back to the blood. Mn exposure alters these processes, leading to Cu dyshomeostasis-associated neuronal injury.
| S-EPMC4064014 | biostudies-literature
Project description:Our knowledge on the release of copper from Cu-thionein in biological systems is limited. Other than oxidative cleavage or direct transfer, the possibility of an alkylation mechanism seemed attractive. Iodoacetamide and methyl methanesulphonate were successfully employed to alkylate the Cu-thiolate sulphur atom of homogeneous Cu(I)-thionein from yeast. The alkylation caused a weakening of the Cu-S bonding, which led to the release of copper. After equilibrium dialysis a proportion of the released copper was found in the dialysis buffer. When iodoacetamide was used carboxymethylcysteine was detected in the protein hydrolysate. A 10-fold molar excess over cysteine was sufficient for complete alkylation, which could be conveniently monitored by c.d. at 328 and 359 nm. The reaction proceeded under both aerobic and anaerobic conditions. E.p.r. measurements of Cu2+ revealed unequivocally the complete cleavage of the Cu-thiolate bonding in less than 5 h. It is possible that this mode of copper release might be of relevance to the molecular transport of this biochemically important transition metal.
| S-EPMC1149182 | biostudies-other
Project description:The copper-sensing operon repressor (CsoR) is representative of a major Cu(I)-sensing family of bacterial metalloregulatory proteins that has evolved to prevent cytoplasmic copper toxicity. It is unknown how Cu(I) binding to tetrameric CsoRs mediates transcriptional derepression of copper resistance genes. A phylogenetic analysis of 227 DUF156 protein members, including biochemically or structurally characterized CsoR/RcnR repressors, reveals that Geobacillus thermodenitrificans (Gt) CsoR characterized here is representative of CsoRs from pathogenic bacilli Listeria monocytogenes and Bacillus anthracis. The 2.56 Å structure of Cu(I)-bound Gt CsoR reveals that Cu(I) binding induces a kink in the α2-helix between two conserved copper-ligating residues and folds an N-terminal tail (residues 12-19) over the Cu(I) binding site. NMR studies of Gt CsoR reveal that this tail is flexible in the apo-state with these dynamics quenched upon Cu(I) binding. Small angle x-ray scattering experiments on an N-terminally truncated Gt CsoR (Δ2-10) reveal that the Cu(I)-bound tetramer is hydrodynamically more compact than is the apo-state. The implications of these findings for the allosteric mechanisms of other CsoR/RcnR repressors are discussed.
| S-EPMC4081955 | biostudies-literature
Project description:Previous studies have suggested that copper is incompletely incorporated into caeruloplasmin, the major plasma form of copper-transporting protein, in the genetic copper toxic condition, Wilson's disease. In this paper we have investigated the role of copper and caeruloplasmin in the abnormal biliary copper transport and characterizes Wilson's disease. Using SDS/PAGE and Western blotting, we have demonstrated the presence of holocaeruloplasmin in liver samples from patients with Wilson's disease (abnormal biliary copper excretion) and in control patients (normal biliary copper excretion). The presence of holocaeruloplasmin was also confirmed by measurement of caeruloplasmin oxidase activity using staining with o'Dianisidine. In contrast with the findings in liver tissue, holocaeruloplasmin was absent from bile from patients with Wilson's disease, but as expected it was present in the bile from control subjects. We have also identified and partially characterized a 189-200 kDa protein from purified human biliary canalicular membranes which binds copper and possesses caeruloplasmin-like activity when probed with a specific human anti-caeruloplasmin antibody. In conclusion, we have demonstrated that copper incorporation in caeruloplasmin is normal in patients with Wilson's disease contrary to previous reports. Secondly, we have shown that the defect in Wilson's disease appears to lie in the biliary canalicular excretion of holocaeruloplasmin resulting in its retention within the hepatocyte causing copper toxicosis. Finally we have identified and partially characterized a caeruloplasmin-binding protein from biliary canalicular membranes which may provide a link to the gene defect in Wilson's disease.
| S-EPMC1217284 | biostudies-other
Project description:K562 cells, a human erythroleukaemic cell line blocked for differentiation, commit towards erythrocytes when exposed to haemin (20 microM). The cells synthesize fetal haemoglobins and show site-specific binding of caeruloplasmin, a plasma copper protein. These events are set into motion by haemin. On the assumption that the binding of caeruloplasmin could reflect a greater need for copper, we sought to determine whether the transfer of 67Cu from caeruloplasmin was accelerated in haemin-induced compared with non-induced K562 cells. Cu,Zn superoxide dismutase (CuZnSOD) was the recipient. Haemin induction caused the K562 cells to lose CuZnSOD activity. By 96 h, the level of SOD activity was less than 60% of that of non-induced cells. The loss was confined entirely to the CuZn form, MnSOD activity staying essentially unchanged. Although CuZnSOD activity declined with the haemin induction, the incorporation of [4,5-3H]lysine into immunoprecipitable CuZnSOD protein was unaffected. There was also no change in CuZnSOD mRNA concentration in haemin-induced cells. Thus a loss of enzyme did not correlate with a decline in the synthesis de novo of CuZnSOD protein. When 48 h-induced cells were transferred to a medium supplemented with 0.2 microM-caeruloplasmin, CuZnSOD activity was restored to control levels in 24 h. Caeruloplasmin also stimulated the incorporation of [3H]lysine into immunoprecipitable CuZnSOD protein. Caeruloplasmin addition may have affected a post-translational regulatory site for CuZnSOD biosynthesis, possibly by providing copper for the newly synthesized enzyme.
| S-EPMC1150191 | biostudies-other