Hg-binding Protein Research Articles

Versatile artificial mer operons in Escherichia coli towards whole cell biosensing and adsorption of mercury.

Mercury exists naturally and mainly as a man-made pollutant in the environment, where it exerts adverse effects on local ecosystems and living organisms. It is important to develop an appropriate synthetic biological device that recognizes, detects and removes the bioavailable fraction of environmental mercury. Both single-signal and double-signal output mercury biosensors were assembled using a natural mer operon as a template. Selectivity and sensitivity of whole-cell biosensors based on artificial mer operons were determined. Three whole-cell biosensors were highly stable at very high concentrations of mercuric chloride, and could detect bioavailable Hg(II) in the concentration range of 6.25–200 μM HgCl2. A novel Hg(II) bioadsorption coupled with biosensing artificial mer operon was assembled. This would allow Hg(II)-induced Hg(II) binding protein cell surface display and green fluorescence emission to be achieved simultaneously while retaining the linear relationship between fluorescent signal and Hg(II) exposure concentration. The present study provides an innovative way to simultaneously detect, quantify, and remove bioavailable heavy metal ions using an artificially reconstructed heavy metal resistance operon.

Unveiling Hg-binding protein within black deposit formed on Golgi-Cox-stained brain neuron

BackgroundGolgi-Cox staining has been conventionally used for investigating neuronal development. After the brain tissue is subject to Golgi-Cox staining, black deposits are formed on the surface of the stained neurons because of mercuric sulfide, which does not show a fluorescence response under two-photon excitation. However, we unexpectedly observed fluorescence emitted by these black deposits during two-photon fluorescence measurements. Further, the in-depth of physical and chemical methods analysis revealed that the black deposits on the stained neurons are composed of Hg-binding proteins. MethodsWe studied black deposits present in the Golgi-Cox-stained mouse brain neurons using techniques such as multiple-photon microscopy, scan electron microscopy, micro-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. ResultsThe emitted fluorescence was because of the fluorescence groups of Hg-binding protein present within the Golgi-Cox deposits on the neuronal surface. ConclusionsThe presence of Hg-binding proteins within black deposits on the surface of Golgi-Cox-stained neurons was proven for the first time. The novel interaction between the neurons and Hg2+ ions during Golgi-Cox staining help to understand the mechanism of Golgi-Cox staining.

Characterization of the mercury-binding proteins in tuna and salmon sashimi: Implications for health risk of mercury in food

Fish consumption is one of the major ways through which humans receive exposure to mercury (Hg). The existing forms of Hg in food, particularly Hg bound to proteins, may affect the absorption of Hg by humans and subsequently its potentially toxic effects. However, the knowledge regarding Hg-binding proteins in edible fish muscle is scarce. In the present study, salmon and tuna fish muscles, collected from seven different regions and countries, were analyzed using metallomics- and proteomics-based techniques. The concentration of Hg in sashimi samples ranged from 4.4 to 317.4 ng/g. Size exclusion chromatography (SEC) coupled with inductively coupled plasma mass spectrometer (ICP-MS) showed that beta-actin was a novel Hg-binding protein from the fish muscles, and this protein could also bind bismuth (Bi), silver (Ag), and copper (Cu). Hg bound to beta-actin accounted for approximately 30.2–37.6% of the total Hg in the tuna muscles and was significantly correlated to total Hg in the fish muscles (r = 0.98, p < 0.01) and in the fraction of soluble proteins (r = 0.94, p < 0.01). These findings suggest that proteins act as the main Hg accumulation sites in edible fish; thus, increasing human exposure to Hg following gastrointestinal digestion.

Solution structures of the reduced and Cu(I) bound forms of the first metal binding sequence of ATP7A associated with Menkes disease

The coding sequence for the first N-terminal copper binding motif of the human Menkes disease protein (MNK1; residues 2-79) was synthesized, cloned, and expressed in bacteria for biochemical and structural studies. MNK1 adopts the betaalphabetabetaalphabeta fold common to all the metal binding sequences (MBS) found in other metal transport systems (e.g., the yeast copper chaperone for superoxide dismutase CCS, the yeast copper chaperone ATX1 bound to Hg(II), and most recently Cu(I), the bacterial copper binding protein, CopZ, and the bacterial Hg(II) binding protein MerP), although substantial differences were found in the metal binding loop. Similar to ATX1, MNK1 binds Cu(I) in a distorted linear bicoordinate geometry. As with MerP, MNK1 has a high affinity for both Hg(II) and Cu(I), although it displays a marked preference for Cu(I). In addition, we found that F71 is a key residue in the compact folding of MNK1, and its mutation to alanine results in an unfolded structure. The homologous residue in MerP has also been mutated with similar results. Finally, to understand the relationship between protein folding and metal affinity and specificity, we expressed a chimeric MBS with the MNK1 protein carrying the binding motif of MerP (CAAC-MNK1); this chimeric protein showed differences in structure and the dynamics of the binding site that may account for metal specificity.

Synthesis Pattern of an Hg-Binding Protein in Acetabularia calyculus During Short-Term Exposure to Mercury

Synthesis Pattern of an Hg-Binding Protein in Acetabularia calyculus During Short-Term Exposure to Mercury

Synthesis pattern of an Hg-binding protein in Acetabularia calyculus during short-term exposure to mercury.

Synthesis pattern of an Hg-binding protein in Acetabularia calyculus during short-term exposure to mercury.

Studies on Protective Effect of Mercurial Toxicity by Selenium. III. Reaction Mechanism of Mercury with Selenium in Plasma of Rats simultaneously injected Mercuric Chloride and Sodium Selenite

The reaction mechanism of mercury with selenium in the plasma of rats simultaneously injected HgCl2 and Na2SeO3 was investigated. Sera collected after independent or simultaneous injection of HgCl2 (10 μmol/kg, i.p. or i.v.) and Na2SeO3 (10 μmol/kg, s.c.) were chromatographed on Sephadex G-200 column. Distribution of mercury and selenium in the serum protein fractions of each injection group was determined by atomic absorption analysis and neutron activation analysis. On the other hand, bovine serum albumin, reduced glutathione, Na2SeO3, and HgCl2 were reacted as the model reaction of mercury with selenium in the plasma. The reaction product of mercury with selenium in this reaction was chromatographed on Sephadex G-200 column and compared with in vivo experimental results. These results suggested that the final reaction product of mercury with selenium in the plasma was a colloidal HgSe, formed by the following two reactions : (1) Mercury from the Hg-binding protein transfers to the Se-binding protein and forms an intermediate such as protein-S-Se-Hg+. (2) The Hg-binding protein reacts with the Se-binding protein and forms an intermediate such as protein-S-Hg-Se-S-protein, or selenium from the Se-binding protein transfers to the Hg-binding protein and forms an intermediate such as protein-S-Hg-Se-. Finally, these intermediates decompose to HgSe and then it converts to colloidal HgSe by association. The latter reaction was proved to occur in the plasma after simultaneous injection of HgCl2 (i.v.) and Na2SeO3 (s.c.).