Cd-binding Protein Research Articles

Assessment of 13 essential and toxic trace elements in tumor and peritumoral brain tissues from human glioblastoma.

Trace elements within the brain are important for proper neurological function, but their imbalance has been rarely investigated in glioblastoma. This study enrolled a total of 14 patients with glioblastoma, and the tumor and peritumoral brain tissues were collected while undergoing surgery. The concentrations of Mg, Ca, Cr, Mn, Fe, Co, Cu, Zn, Se, As, Cd, Tl and Pb were determined using a well-evaluated ICP-MS method. The Cu- and Cd-binding proteomes were further analyzed using the anatomic transcriptional atlas from Ivy GAP. Histological evaluation was based on rubeanic acid staining and immunohistochemistry, respectively. The 13 trace element concentrations were obtained, and the highest were Ca, Mn, Fe, Zn and Cu, ranging from a few to dozens of ug/g. Correlation analysis suggested the existence of two intra-correlated clusters: essential metals (Cu-Ca-Zn-Mg) and heavy metals (Pb-As-Cd-Tl-Co-Cr-Mn). Compared to the tumor samples, significantly higher levels of Cu and Cd were observed in the peritumoral region. Further analysis of the Cu- and Cd-binding proteins from the anatomic view suggested that DBH and NOS1 were obviously increased in the leading edge than the central tumor region. Consistent with the above findings, histological evaluation of Cu and DBH further confirmed more copper and DBH expressions in the peritumoral area compared to the tumor core. Trace elements differ in tumor and peritumoral brain zone in glioblastoma, which may associate with tumor angiogenesis.

In Silico Identification of Cadmium Binding Protein and its Secreted Metalloproteins in Stenotrophomonas maltophilia

Background: Stenotrophomonas maltophilia is a pathogenic bacteria that causes serious infectious complications in humans, especially in immune-compromised patients. Stenotrophomonas maltophilia is a gram-negative bacterium that is multidrug-resistant. Objective: The purpose of the study is to understand the diverse cellular and biological functions of cadmium-binding metalloproteins and to predict their role in pathogenicity, regulation, and growth. Methodology: Different in silico approaches were used to check the Functional Annotation, Subcellular Localization, Gene Ontology, and Bacterial toxin prediction have been used to identify the cellular and biological function of Cd-binding metalloproteins in Stenotrophomonas maltophilia. Results: Identified 116 Cd-binding proteins from the whole proteome sequence and functional domain, family, localization, and toxicity were also studied. Conclusion: The outcomes revealed that this study could be used in understanding the 116 cadmiumbinding proteins from the whole proteome sequence. This study shows the survival, growth, and pathogenicity of the bacteria.

A Coculture of Enterobacter and Comamonas Species Reduces Cadmium Accumulation in Rice.

The accumulation of cadmium (Cd) in plants is strongly impacted by soil microbes, but its mechanism remains poorly understood. Here, we report the mechanism of reduced Cd accumulation in rice by coculture of Enterobacter and Comamonas species. In pot experiments, inoculation with the coculture decreased Cd content in rice grain and increased the amount of nonbioavailable Cd in Cd-spiked soils. Fluorescence in situ hybridization and scanning electron microscopy detection showed that the coculture colonized in the rhizosphere and rice root vascular tissue and intercellular space. Soil metagenomics data showed that the coculture increased the abundance of sulfate reduction and biofilm formation genes and related bacterial species. Moreover, the coculture increased the content of organic matter, available nitrogen, and potassium and increased the activities of arylsulfatase, β-galactosidase, phenoloxidase, arylamidase, urease, dehydrogenase, and peroxidase in soils. In subsequent rice transcriptomics assays, we found that the inoculation with coculture activated a hypersensitive response, defense-related induction, and mitogen-activated protein kinase signaling pathway in rice. Heterologous protein expression in yeast confirmed the function of four Cd-binding proteins (HIP28-1, HIP28-4, BCP2, and CID8), a Cd efflux protein (BCP1), and three Cd uptake proteins (COPT4, NRAM5, and HKT6) in rice. Succinic acid and phenylalanine were subsequently proved to inhibit rice divalent Cd [Cd(II)] uptake and activate Cd(II) efflux in rice roots. Thus, we propose a model that the coculture protects rice against Cd stress via Cd immobilization in soils and reducing Cd uptake in rice. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

A metal chaperone OsHIPP16 detoxifies cadmium by repressing its accumulation in rice crops

Cadmium (Cd) is an environmentally polluted toxic heavy metal and seriously risks food safety and human health through food chain. Mining genetic potentials of plants is a crucial step for limiting Cd accumulation in rice crops and improving environmental quality. This study characterized a novel locus in rice genome encoding a Cd-binding protein named OsHIPP16, which resides in the nucleus and near plasma membrane. OsHIPP16 was strongly induced by Cd stress. Histochemical analysis with pHIPP16::GUS reveals that OsHIPP16 is primarily expressed in root and leaf vascular tissues. Expression of OsHIPP16 in the yeast mutant strain ycf1 sensitive to Cd conferred cellular tolerance. Transgenic rice overexpressing OsHIPP16 (OE) improved rice growth with increased plant height, biomass, and chlorophyll content but with a lower degree of oxidative injury and Cd accumulation, whereas knocking out OsHIPP16 by CRISPR-Cas9 compromised the growth and physiological response. A lifelong trial with Cd-polluted soil shows that the OE plants accumulated much less Cd, particularly in brown rice where the Cd concentrations declined by 11.76–34.64%. Conversely, the knockout oshipp16 mutants had higher levels of Cd with the concentration in leaves being increased by 26.36–35.23% over the wild-type. These results suggest that adequate expression of OsHIPP16 would profoundly contribute to Cd detoxification by regulating Cd accumulation in rice, suggesting that both OE and oshipp16 mutant plants have great potentials for restricting Cd acquisition in the rice crop and phytoremediation of Cd-contaminated wetland soils.

Identification and functional analysis of cadmium-binding protein in the visceral mass of Crassostrea gigas

The Pacific oyster, Crassostrea gigas, is a traditional food worldwide. The soft body of the oyster can easily accumulate heavy metals such as cadmium (Cd). To clarify the molecular mechanism of Cd accumulation in the viscera of C. gigas, we identified Cd-binding proteins. 5,10,15,20-Tetraphenyl-21H,23H-porphinetetrasulfonic acid, disulfuric acid, tetrahydrate, and Cd-binding competition experiments using immobilized metal ion affinity chromatography revealed the binding of water-soluble high molecular weight proteins to Cd, including C. gigas protein disulfide isomerase (cgPDI). Liquid chromatography–tandem mass spectrometry (LC–MS/MS) analyses revealed two CGHC motifs in cgPDI. The binding between Cd and rcgPDI was confirmed through a Cd-binding experiment using the TPPS method. Isothermal titration calorimetry (ITC) revealed the binding of two Cd ions to one molecule of rcgPDI. Circular dichroism (CD) spectrum and tryptophan fluorescence analyses demonstrated that the rcgPDI bound to Cd. The binding markedly changed the two-dimensional or three-dimensional structures. The activity of rcgPDI measured by a PDI Activity Assay Kit was more affected by the addition of Cd than by human PDI. Immunological analyses indicated that C. gigas contained cgPDI at a concentration of 1.0 nmol/g (viscera wet weight). The combination of ITC and quantification results revealed that Cd-binding to cgPDI accounted for 20% of the total bound Cd in the visceral mass. The findings provide new insights into the defense mechanisms of invertebrates against Cd.

Cadmium species in marine short-necked clam analyzed by size exclusion chromatography hyphenated respectively with inductively coupled plasma mass spectrometry and electrospray ionization quadrupole - time of flight mass spectrometry

To date, the speciation analysis of heavy metals in organs is still a challenge because these species are labile in vitro and scarce of the reference materials. In the present study, cadmium (Cd) species in marine shellfish were investigated with size exclusion chromatography (SEC) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS), by which three Cd species in marine short-necked clam were observed. After pre-fractionation with a home-made Sephadex column, the Cd binding species were further characterized with SEC coupled with electrospray ionization quadrupole - time of flight mass spectrometry (ESI-Q-TOF-MS). The results showed that Cd species with 32,695 Da was the maximum Cd-binding molecule in the clam. Several metallothionein (MTs)-like Cd-binding proteins including a main species with molecular weight of 19,236 Da were observed. Some small Cd species with molecular weights less than 1000 Da were also observed in the clam. In order to verify the reliability of the two hyphenated methods, a standard reference material of Zn-binding MTs was analyzed at the same conditions. The results demonstrated that the two hyphenated methods of SEC-ICP-MS and SEC-ESI-Q-TOF-MS were practical to characterize the Cd species in marine shellfish.

Development of Cadmium Multiple-Signal Biosensing and Bioadsorption Systems Based on Artificial Cad Operons.

The development of genetic engineering, especially synthetic biology, greatly contributes to the development of novel metal biosensors. The cad operon encoding cadmium resistance was previously characterized from Pseudomonas putida. In this study, single-, dual-, and triple-signal output Cd(II) biosensors were successfully developed using artificial translationally coupled cad operons. Sensitivity, selectivity, and response toward Cd(II) and Hg(II), of three biosensors were all determined. Reporter signals of three biosensors all increased within the range 0.1–3.125 μM Cd(II). Three biosensors responded strongly to Cd(II), and weakly to Hg(II). However, the detection ranges of Cd(II) and Hg(II) do not overlap in all three biosensors. Next, novel Cd(II) biosensing coupled with bioadsorptive artificial cad operons were assembled for the first time. Cd(II)-induced fluorescence emission, enzymatic indication, and Cd(II) binding protein surface display can be achieved simultaneously. This study provides an example of one way to realize multiple signal outputs and bioadsorption based on the redesigned heavy metal resistance operons, which may be a potential strategy for biodetection and removal of toxic metal in the environment, facilitating the study of the mechanism and dynamics of bioremediation.

Host-Guest Protein Assembly for Affinity Purification of Methyllysine Proteomes.

Protein-protein interactions drive self-assembly of biomacromolecules and thus enable important physiological functions at a cellular level. Supramolecular chemists have developed artificial host-guest interactions that are similar with, yet distinct from and orthogonal to, the natural protein-protein interactions. For instance, cucurbit[n]urils are synthetic receptors that can specifically recognize proteins with N-terminal aromatic residues with high affinities, yet this interaction can be reversed by the competition of small molecules such as amantadine. Herein, we develop a site-specific, oriented protein-display method by combining the host-guest interaction based on cucurbit[7]uril and a covalent protein-peptide reaction. A methyllysine-binding protein HP1β chromodomain (CD) is immobilized via host-guest interactions and used as the "bait" to capture methyllysine proteomes from cancer cells. The captured "fish"-methyllysine-containing proteins-can be released via competitive displacement by amantadine in a nondenaturing and traceless manner. This affinity purification method found 73 novel methyllysine sites from 101 identified sites among 66 methylated proteins from 255 HP1β CD-binding proteins in cancer cells via subsequent mass spectrometric analysis. This work thereby presents a new strategy of artificial host-guest protein assembly in affinity purification of methyllysine proteins in coupling to mass spectrometry.

Screening of the proteins related to the cultivar-dependent cadmium accumulation of Brassica parachinensis L.

Cultivar-dependent cadmium (Cd) accumulation was principal in developing Cd-pollution safe cultivars (PSCs). Proteins related to different Cd accumulations of the low-Cd-accumulating (SJ19) and high-Cd-accumulating (CX4) cultivars were investigated by iTRAQ analysis. Higher Cd bioaccumulation factors and translocation factor in CX4 than in SJ19 were consistent with the cultivar-dependent Cd accumulations. The Cd uptake was promoted in CX4 due to its higher expression of Cd-binding proteins and the lower expression of Cd-efflux proteins in roots. What's more, significantly elevated thiol groups (PC2 and PC3) in CX4 under Cd stress might contribute to the high Cd accumulation in roots and the root-to-shoot translocation of Cd-PC complex. Up-regulated proteins involved in cellulose biosynthesis and pectin de-esterification in SJ19 enhanced the Cd sequestration of root cell walls, which was considered as the predominant strategy for reducing Cd accumulation in shoots. The present study provided novel insights in the cultivar-dependent Cd accumulation in shoots of B. parachinensis.

Proteomics and bioinformatics analysis reveal potential roles of cadmium-binding proteins in cadmium tolerance and accumulation of Enterobacter cloacae.

BackgroundEnterobacter cloacae (EC) is a Gram-negative bacterium that has been utilized extensively in biotechnological and environmental science applications, possibly because of its high capability for adapting itself and surviving in hazardous conditions. A search for the EC from agricultural and industrial areas that possesses high capability to tolerate and/or accumulate cadmium ions has been conducted in this study. Plausible mechanisms of cellular adaptations in the presence of toxic cadmium have also been proposed.MethodsNine strains of EC were isolated and subsequently identified by biochemical characterization and MALDI-Biotyper. Minimum inhibitory concentrations (MICs) against cadmium, zinc and copper ions were determined by agar dilution method. Growth tolerance against cadmium ions was spectrophotometrically monitored at 600 nm. Cadmium accumulation at both cellular and protein levels was investigated using atomic absorption spectrophotometer. Proteomics analysis by 2D-DIGE in conjunction with protein identification by QTOF-LC-MS/MS was used to study differentially expressed proteins between the tolerant and intolerant strains as consequences of cadmium exposure. Expression of such proteins was confirmed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Bioinformatics tools were applied to propose the functional roles of cadmium-binding protein and its association in cadmium tolerance mechanisms.ResultsThe cadmium-tolerant strain (EC01) and intolerant strain (EC07) with the MICs of 1.6 and 0.4 mM, respectively, were isolated. The whole cell lysate of EC01 exhibited approximately two-fold higher in cadmium binding capability than those of the EC07 and ATCC 13047, possibly by the expression of Cd-binding proteins. Our proteomics analysis revealed the higher expression of DUF326-like domain (a high cysteine-rich protein) of up to 220 fold in the EC01 than that of the EC07. Confirmation of the transcription level of this gene by qRT-PCR revealed a 14-fold induction in the EC01. Regulation of the DUF326-like domain in EC01 was more pronounced to mediate rapid cadmium accumulation (in 6 h) and tolerance than the other resistance mechanisms found in the ATCC 13047 and the EC07 strains. The only one major responsive protein against toxic cadmium found in these three strains belonged to an antioxidative enzyme, namely catalase. The unique proteins found in the ATCC 13047 and EC07 were identified as two groups: (i) ATP synthase subunit alpha, putative hydrolase and superoxide dismutase and (ii) OmpX, protein YciF, OmpC porin, DNA protection during starvation protein, and TrpR binding protein WrbA, respectively.ConclusionAll these findings gain insights not only into the molecular mechanisms of cadmium tolerance in EC but also open up a high feasibility to apply the newly discovered DUF326-like domain as cadmium biosorbents for environmental remediation in the future.

Affinity Purification of Methyllysine Proteome by Site-Specific Covalent Conjugation.

A basic but critical step in targeted proteomics by mass spectrometry is the separation of the targeted proteins from the complex mixture of the whole proteome by affinity purification. The bait protein is usually immobilized on the surface of a solid support to enable affinity-based purification of the targeted proteome. Here, we developed a site-specific covalent immobilization of the bait protein through affinity-guided covalent coupling (AGCC) of a single cysteine residue of an SH2 domain (utilized as an affinity tag for the protein target) with an engineered ligand peptide. Site-specific covalent immobilization of a methyllysine-binding protein HP1β chromodomain on the agarose resin was used to purify the methyllysine proteome from the whole-protein mixture. This new bait immobilization led to a notably low background in the affinity purification step, markedly outperforming the conventional (His)6 tag-nickel nitrilotriacetic acid (Ni-NTA) immobilization method. Subsequent analysis of the purified proteome identified 275 lysine methylated sites and 184 methylated proteins from 332 HP1β CD-binding proteins, including 30 novel methylated proteins. This work demonstrates that a robust site-specific covalent protein immobilization method is well-suited for proteomic analysis of low-abundance proteins. This method also enables the identification of new methylated proteins and methylation sites in the methyllysine proteome.

Preliminary results from structural systems biology approach in Tetrahymena thermophila reveal novel perspectives for this toxicological model.

Tetrahymena is a unicellular microbial eukaryotic organism that has been used extensively in toxicology and environmental research. This work attempts to model for the first time the wiring of proteins involved in cellular mechanisms of Cd toxicity in Tetrahymena thermophila. 1975 high-confidence PPIs between 68 Cd-binding proteins and 422 partners were inferred through a novel structural systems biology approach that utilizes comparative analysis between Tetrahymena and other eukaryotes for which experimentally supported protein interactomes exist. The PPIs of the potential network were confirmed by known domain interactions in the Protein Data Bank and its topological characteristics were compared with publicly available experimental information for T. thermophila. To experimentally validate the robustness of the proposed PPI network, the interaction between the two most interconnected hub proteins was detected through GST pull-down assay. Potential effects on Tetrahymena's cellular and metabolic processes by PPIs involving Cd-binding proteins were uncovered. Furthermore, 244 PPIs in which Cd-binding proteins or/and their partners are encoded by orthologs of human disease genes in T. thermophila, but not in yeast, were identified and analyzed. The findings suggest that Tetrahymena could be possibly a useful model for an improved understanding of molecular mechanisms of Cd toxicity in human diseases.

Cadmium Distribution and Characteristics of Cadmium-binding Proteins in Rice (<i>Oryza sativa L.</i>) Kernel

Studies were performed to investigate the Cadmium (Cd) distribution and Cd-binding proteins in rice kernel. Rice seeds [Oryza sativa L. (Akitakaomachi)] were cultured under Cd stress and after harvesting, the Cd distribution was determined using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The Cd concentrations and amino acid compositions in different storage protein fractions were analyzed using ICP-MS and an amino acid analyzer, respectively. The molecular weights of the Cd-binding proteins were determined by size exclusion chromatography-inductively coupled plasma mass spectrometry (SEC-ICP-MS). The Cd concentrations in rice kernel gradually decreased from the outer bran layers to the endosperm and Cd was particularly concentrated in the embryo, the outer pericarp and the aleurone layer. The Cd concentrations in different proteins fractions decreased in the following sequence: globulin > albumin > glutelin > prolamin. The presence of cysteine and methionine were closely related to the Cd concentration. The molecular weights of three prominent Cd-binding protein fractions were > 2000 k Da, 570 k Da and 131.9 k Da, respectively.

Expression of cadR Enhances its Specific Activity for Cd Detoxification and Accumulation in Arabidopsis.

Cadmium (Cd) is a transition metal that is highly toxic in biological systems. Anthropogenic emissions of Cd have increased biogeochemical cycling and the amount of Cd in the biosphere. Here we studied the utility of a bacterial Cd-binding protein, CadR, for the remediation of Cd contamination. CadR was successfully targeted to chloroplasts using a constitutive Cauliflower mosaic virus (CaMV) 35S promoter or a shoot-specific Chl a/b-binding protein 2 gene (CAB2) promoter and an RbcS (small subunit of the Rubisco complex) transit peptide. Under short-term (2 d) exposure to Cd, the cadR transgenic plants showed up to a 2.9-fold Cd accumulation in roots compared with untransformed plants. Under medium term (7 d) exposure to Cd, the concentrations of Cd in leaves began to increase but there were no differences between the wild type and the cadR transgenic plants. Under long-term (16 d) exposure to Cd, the cadR transgenic plants accumulated greater amounts of Cd in leaves than the untransformed plants. Total Cd accumulation (µg per plant) in shoots and roots of the plants expressing cadR were significantly higher (up to 3.5-fold in shoots and 5.2-fold in roots) than those of the untransformed plants. We also found that targeting CadR to chloroplasts facilitated chloroplastic metal homeostasis and Chl b accumulation. Our results demonstrate that manipulating chelating capacity in chloroplasts or in the cytoplasm may be effective in modifying both the accumulation of and resistance to Cd.

Characterization of a novel gene involved in cadmium accumulation screened from sponge-associated bacterial metagenome

Metagenome research has brought much attention for the identification of important and novel genes of industrial and pharmaceutical value. Here, using a metagenome library constructed from bacteria associated with the marine sponge, Styllisa massa, a high-throughput screening technique using radioisotope was implemented to screen for cadmium (Cd) binding or accumulation genes. From a total of 3301 randomly selected clones, a clone 247-11C was identified as harboring an open reading frame (ORF) showing Cd accumulation characteristics. The ORF, termed as ORF5, was further analyzed by protein functional studies to reveal the presence of a protein, Cdae-1. Cdae-1, composed of a signal peptide and domain harboring an E(G/A)KCG pentapeptide motif, enhanced Cd accumulation when expressed in Escherichia coli. Although showing no direct binding to Cd in vitro, the presence of important amino acid residues related to Cd detoxification suggests that Cdae-1 may possess a different mechanism from known Cd binding proteins such as metallothioneins (MTs) and phytochelatins (PCs). In summary, using the advantage of bacterial metagenomes, our findings in this work suggest the first report on the identification of a unique protein involved in Cd accumulation from bacteria associated with a marine sponge.

Relationship between biomass, seed components and seed Cd concentration in various peanut (Arachis hypogaea L.) cultivars grown on Cd-contaminated soils

Peanuts (Arachis hypogaea L.) exhibit high genotypic variations in seed Cd accumulation, but the mechanism remains unclear. This study aimed to reveal the main factors that determine Cd concentration in peanut seeds. The biomasses and Cd accumulation in plant tissues as well as the Cd distribution in the seeds of 15 peanut cultivars were analyzed in a pot experiment at 4mgkg−1 Cd (treatment) and 0mgkg−1 Cd (control). Peanuts exhibited large variations among cultivars in terms of Cd accumulation and distribution at the whole-plant and seed levels. The peanut cultivars were divided into three groups based on [Cd]embryos as follows: (i) high Cd accumulators (Zhenghong 3 and Haihua 1), (ii) low Cd accumulators (Qishan 208, Luhua 8, and Yuhua 15), and (iii) intermediate Cd accumulators (10 remaining cultivars). [Cd]embryos was significantly correlated with [Cd]testae and [Cd]oils at control conditions, whereas in the 4mgkg−1 Cd treatment, [Cd]embryos was negatively correlated with plant biomass, total Cd and its proportion in vegetative organs, and seed oil contents. [Cd]embryos was positively correlated with protein contents, [Cd]oils, and proportion of Cd in protein extracts at 4mgkg−1 Cd treatments. The attenuation of Cd by high biomass of vegetative tissues and Cd-binding proteins in seeds mainly determined the Cd concentration in peanut seeds.

Evolution of metallotionein isoforms complexes in hepatic cells of Mus musculus along cadmium exposure

Characterization of Cd-binding proteins has great analytical interest due to the high toxicity of Cd to living organisms. Metallothioneins (MTs), as Cd(II)-binding proteins are of increasing interest, since they form very stable Cd chelates and are involved in many detoxification processes. In this work, inductively coupled plasma octopole reaction cell mass spectrometry and nanospray ionization time-of-flight mass spectrometry were used in parallel and combined with two-dimensional chromatography: size exclusion followed by reversed-phase high performance liquid chromatography, to study metal complexes of MT isoforms produced in hepatic cytosols of Mus musculus during exposure experiments to Cd. Exposure experiments were carried out by subcutaneous injection of a growing dose of the toxic element ranging from 0.1 to 1.0mg of Cd per kg of body weight per day during 10days. A control group and three exposure groups at days 2, 6 and 10 of exposure were studied, and different cadmium, copper and zinc complexes with MTs isoforms were isolated and characterized from the two most exposed groups. The results allow gaining insight into the mechanisms involved in metal detoxification by MTs, showing the changes in the stoichiometry of metal complexes-MTs along cadmium exposure.

Metallothionein-like proteins induced by cadmium stress in the scallop Mizuhopecten yessoensis

Organisms have evolved a cellular response called stress protein response that increases their tolerance in adverse environmental conditions. Well known stress proteins that bind essential and toxic metals are metallothionein (MT). The scallop Mizuhopecten yessoensis is the most interesting organism because it is able to accumulate toxic cadmium in its digestive gland. However, in the tissue of the digestive gland of Mizuhopecten yessoensis MT (metallothioneins) have not been found. Eastern scallops, Mizuhopecten yessoensis, were collected from two locations — one clean and one polluted site. The concentrations of cadmium (Cd), copper (Cu) and zinc (Zn) were measured in the digestive gland. There was a significant increase in Cd concentrations in this studied tissue. We found that in the presence of cadmium Mizuhopecten yessoensis can induce high molecular proteins. The results of experiments have shown that Cd-binding ligands have a number of properties similar to MT: acetone and temperature stability; the ability to bind some metals, including Cd, Cu and Zn. Protein chromatography (FPLC, Superosa 12) from the digestive gland of scallop M. yessoensis has shown that cadmium is associated with high molecular weight Cd-binding proteins (72 kDa and 43 kDa). The major cadmium-binding protein 72 kDa is glycoprotein. In experiments we have demonstrated that Cd-binding proteins can be induced when there is cadmium exposure. The results of this study strongly suggest that the far eastern scallop Mizuhopecten yessoensis has a unique and well-developed system for the detoxification of heavy metals and it allows for biochemical systems to be maintained in a relatively stable manner in the presence of heavy metals.

The Influence of Cadmium Stress on the Content of Mineral Nutrients and Metal-Binding Proteins in Arabidopsis halleri.

We investigated the influence of cadmium stress on zinc hyperaccumulation, mineral nutrient uptake, and the content of metal-binding proteins in Arabidopsis halleri. The experiments were carried out using plants subjected to long-term cadmium exposure (40 days) in the concentrations of 45 and 225 μM Cd2+. Inductively coupled plasma-mass spectrometry, size exclusion chromatography coupled with plasma-mass spectrometry, and laser ablation inductively coupled plasma-mass spectrometry used for ablation of polyacylamide gels were employed to assess the content of investigated elements in plants as well as to identify metal-binding proteins. We found that A. halleri is able to translocate cadmium to the aerial parts in high amounts (translocation index >1). We showed that Zn content in plants decreased significantly with the increase of cadmium content in the growth medium. Different positive and negative correlations between Cd content and mineral nutrients were evidenced by our study. We identified more than ten low-molecular-weight (<100 kDa) Cd-binding proteins in Cd-treated plants. These proteins are unlikely to be phytochelatins or metallothioneins. We hypothesize that low-molecular-weight Cd-binding proteins can be involved in cadmium resistance in A. halleri.Electronic supplementary materialThe online version of this article (doi:10.1007/s11270-012-1292-4) contains supplementary material, which is available to authorized users.

Characteristics of minerals extracted from the mid-gut gland of Japanese scallop Patinopecten yessoensis at various pH values

This experiment was carried out to determine the proximate composition of the mid-gut gland (MGG) of the Japanese scallop Patinopecten yessoensis to evaluate the characteristics of divalent minerals and water-soluble protein at various pHs, and to examine Cd-binding protein at different molecular weights. MGG of scallop contained protein, fat and ash of 28.9 g/100 g dry matter, 44.6 g/100 g dry matter and 6.78 g/100 dry matter, respectively. MGG also contained the macrominerals sodium, potassium, magnesium and calcium, and the trace minerals iron, zinc, cadmium and copper. The solubility of divalent minerals and water-soluble protein was high in both acidic and alkaline conditions, except that magnesium was not affected by acidity. The solubility of copper and iron had a positive correlation with water-soluble protein at all pH values, whereas cadmium had a strong correlation at alkaline pH. Low-molecular-weight water-soluble protein (fraction III, 437.5 < MW < 1,355) bound cadmium strongly in acidic, neutral and alkaline conditions. However, in acidic conditions cadmium had the strongest binding to protein.