Characterisation of human metallothioneins from foetal liver and adult kidney using differential pulse polarography

Ruiz, Consuelo; Rodríguez, A. R.

doi:10.1016/s0003-2670(97)00255-9

Cited by 27 publications

(21 citation statements)

References 26 publications

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“…In this figure all peaks which could be found in binary mixtures are presented. The polarographic peaks have been assigned in accordance with former studies on Cd, ZnMT [8][9][10][11][12][13][14][15][16] and on the cadmium and zinc complexed with FT using DPP [18,19,[21][22][23]. Peaks labelled β(Cd) and β(Zn) have been attributed to the oxidation of the mercury electrode in the presence of thiol groups complexed by cadmium and zinc, respectively.…”

Section: Resultssupporting

confidence: 80%

“…These values are comparable to those obtained for Cd, ZnMT of different origin [8,9,11] and for M-FT complexes [18][19][20], M being Cd, Zn or Hg. Even if the assumption on which this estimation is based can be considered as only approximate, the stability constants of the β domain of MT with different metal ions have been estimated here for the first time.…”

Section: Estimation Of Apparent Stability Constants β-Msupporting

confidence: 88%

“…In this figure, the new peak labelled Cdβ' is shown and is attributed to the reduction of cadmium complexed by the β domain in a different complexation form to the Cdβ one. This new peak is labelled Cdβ' by analogy with peaks named CdT and CdT' in the study of MT [8][9][10][11][12][13][14][15][16] and CdFT and CdFT' obtained with the peptidic fragment FT in the presence of cadmium and/or zinc [17][18][19][20][21][22][23][24][25] in previous electrochemical works. Peaks have been resolved as mentioned and it is necessary to point out that, when Zn 2+ is in excess (Fig.…”

Section: Resultsmentioning

confidence: 89%

“…In previous DPP studies with MT [10,11,13,16] and with FT:Cd:Zn [19,20,25], the variation of pH has been seen to play an important role in the stability of one of the two cadmium complexes, CdT and CdT', and CdFT and CdFT'; in fact it is possible to provoke a change or to modify the proportion of both complexes by a mere change of the solution pH. When the pH is increased from 8 to 9.5 the transformation of CdT' peak, obtained in the presence of zinc, into the CdT peak occurs.…”

Section: Influence Of the Ph On The Complexation Forms Of Cadmiummentioning

confidence: 99%

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Complexing properties of the b metallothionein domain with cadmium and/or zinc, studied by differential pulse polarography

Dabrio¹,

Rodríguez²

2000

Analusis

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Mammalian metallothioneins (MT) containing 61 amino acids, of which 20 are cysteine have a structure comprising of two clusters. The α clusters correspond to the C terminal domain of residues 31-61 involving eleven cysteinic residues and the β cluster corresponds to the N-terminal domain of residues 1-30 with nine cysteine residues. All twenty cysteines participate in metal binding. While in the case of MT, their structure and characteristics have been studied using a great variety of analytical methods [1][2][3][4][5][6][7], relatively few studies have been performed with the α and β clusters separately probably due to the difficulties associated with their obtention. In fact these two domains are usually obtained by synthesis using either solid-phase and fragmentcondensation techniques or isolated by proteolysis of metallothioneins of different origin. Nevertheless the use of chemically synthesised and well-characterised separate α and β domains could be very interesting for the study of their metal binding properties and therefore contribute to the understanding of the behaviour of the entire MT.The aim of this research is the systematic study of the complexing properties of the β MT domain with cadmium and/or zinc using electroanalytical methods. These methods have been widely used by our team for the investigation of MT [8][9][10][11][12][13][14][15][16] and related molecules such as the peptidic fragment Lys-Cys-Thr-Cys-Ala (56-61) MT-1 (FT) alone and in the presence of cadmium and/or zinc [17][18][19][20][21][22][23][24][25]. In the case of MT and related molecules, the aminoacid chain is electroactive due to the presence of thiol groups. Moreover, the reduction of the cations, cadmium and zinc, is electrochemically reversible at the mercury electrode and, hence it is possible to obtain three different responses simultaneously for the sample under a given set of experimental conditions. In addition, the electrochemical response depends on the chemical form of the element and allows one to monitor the changes of the different species in solution as a function of different parameters.The β domain has been isolated using different methods [3,7] and its binding properties have been investigated using mainly spectroscopic methods [3,7,[26][27][28][29][30][31][32][33]. The synthesised peptide used in this work has been purchased from the Biochemistry Institute of Zurich University. The purity of this molecule was checked by both Dr. Klauser's team from Zurich University and our team using electrospray ionisation mass spectrometry (ESI-MS) [34,35].The binding properties have been studied, using differential pulse polarography, with different types of additions of metal ions to the apo-β domain and the inverted addition of the β MT domain to metal ions, the gradual addition of metal ions separately and the addition of both cations simultaneously.

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Section: Resultssupporting

confidence: 80%

Section: Estimation Of Apparent Stability Constants β-Msupporting

confidence: 88%

Section: Resultsmentioning

confidence: 89%

Section: Influence Of the Ph On The Complexation Forms Of Cadmiummentioning

confidence: 99%

See 2 more Smart Citations

Complexing properties of the b metallothionein domain with cadmium and/or zinc, studied by differential pulse polarography

Dabrio¹,

Rodríguez²

2000

Analusis

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“…This can be related to NMR data for the rabbit Cd 4 Zn 3 -MT, which revealed a non-uniform distribution of both metals, 68 and electrochemical studies that revealed several forms of human MT in solution depending on Cd 2+ and Zn 2+ concentration. 22 At moderate Cd 2+ load, the calculations reveal a mixture of many isomers. The proteins may affect the relative stability of isomers, mainly spatial constraints from the backbone.…”

Section: Compositions Of Cluster a + B Together In Equilibriummentioning

confidence: 91%

The building blocks of metallothioneins: heterometallic Zn2+ and Cd2+ clusters from first-principles calculations

Jensen

Rykær

2010

Dalton Trans.

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Electronic structures of Zn 2+ and Cd 2+ thiolate clusters found in metallothioneins (MT) have been obtained using density functional theory. We have found that the inherent asymmetry of cluster architectures gives rise to seven distinct metal sites. Whereas the non-strained bond lengths of such tetrathiolate complexes are found to be 2.60Å and 2.39Å for Cd-S and Zn-S, in the MT clusters four characteristic terminal and bridging bonds are observed with average lengths 2.55Å (Cd-S t ); 2.35Å (Zn-S t ); 2.62Å (Cd-S b ); and 2.42Å (Zn-S b ). For each stoichiometry of Zn 2+ and Cd 2+ , all possible isomers have been characterized and ranked according to relative free energy and metal ion selectivity. The most stable distribution at low Cd 2+ concentration is computed to be Zn 4 + CdZn 2 , whereas at 2 : 1 Cd 2+ : Zn 2+ concentration, only heteroclusters are thermodynamically stable, explaining experimental data. The presence of two different clusters in MTs must and can be rationalized already in their intrinsic differences. The results indicate that the asymmetry allows for Zn 2+ transfer to various molecular targets having different thresholds for Zn 2+ binding, while maintaining detoxification sites.

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Voltammetric Methods for Speciation of Plant Metallothioneins

1998

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Cd, Cu and Zn complexes of two synthetically prepared peptides, (g-Glu-Cys) 2 -Gly and (g-Glu-Cys) 3 -Gly, were studied as models of plant metallothioneins by several voltammetric methods. Reduction peak of the complex in which the stechiometric ratio of molar concentrations of Cd(II) and peptide corresponds to coordination of one Cd(II) by four sulfur atoms (E p = ¹814 mV to ¹910 mV, DPV) is suitable for speciation. CSV after adsorption of Cu(I) complex on HMDE is also convenient, and two peaks (E p = ¹817 mV to ¹850 mV and E p = ¹940 mV to ¹953 mV) are attributed to plant MT with Cu(I). Cd and Cu complexes can be distinguished by different dependences for adsorptive accumulation of complexes on HMDE. In both cases the presence of zinc ions interferes with voltammetric speciation. Results of voltammetric studies were applied to the analysis of algal extracts, prepared from alga Chlorella, which was grown in cadmium enriched medium. Successful voltammetric identification of plant metallothionein in this type of material has been performed, in agreement with results from AAS and UV spectroscopy.

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Characterisation of human metallothioneins from foetal liver and adult kidney using differential pulse polarography

Cited by 27 publications

References 26 publications

Complexing properties of the b metallothionein domain with cadmium and/or zinc, studied by differential pulse polarography

Complexing properties of the b metallothionein domain with cadmium and/or zinc, studied by differential pulse polarography

The building blocks of metallothioneins: heterometallic Zn2+ and Cd2+ clusters from first-principles calculations

Voltammetric Methods for Speciation of Plant Metallothioneins

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