Zinc-binding properties of the C-terminal hexapeptide Lys–Cys–Thr–Cys–Cys–Ala from mouse metallothionein: analysis by differential pulse polarography and multivariate curve resolution

Electrochemical behavior of phytochelatins and related peptides at the hanging mercury drop electrode in the presence of cobalt(II) ions

Direct current voltammetry and differential pulse voltammetry have been used to investigate the electrochemical behaviour of two phytochelatins: heptapeptide (gamma-Glu-Cys)3-Gly and pentapeptide (gamma-Glu-Cys)2-Gly, tripeptide glutathione gamma-Glu-Cys-Gly and its fragments: dipeptides Cys-Gly and gamma-Glu-Cys at the hanging mercury drop electrode in the presence of cobalt(II) ions. Most interesting results were obtained with direct current voltammetry in the potential region of -0.80 V up to -1.80 V. Differential pulse voltammetry of the same solutions of Co(II) with peptides gives more complicated voltammograms with overlapping peaks, probably in connection with the influence of adsorption at slow scan rates necessarily used in this method. However, in using Brdicka catalytic currents for analytical purposes, differential pulse voltammograms seem to be more helpful. Presented investigations have shown that particularly the prewave of cobalt(II) allows distinguishing among phytochelatins, glutathione, and its fragments.

Voltammetry assisted by multivariate analysis as a tool for speciation of metallothioneins: competitive complexation of alpha- and beta-metallothionein domains with cadmium and zinc

Multivariate Curve Resolution by Alternating Least Squares (MCR-ALS) is applied to voltammetric data obtained in the study of competitive complexation of Zn(II) and Cd(II) by alpha- and beta-domains of metallothionein (MT). The application of MCR-ALS allows the estimation of both the voltammograms and the concentration profiles associated with each electrochemical process. The complexity of the voltammograms obtained in titrations of the alpha- or beta-domains of MT with Cd(II) and later Zn(II) (or vice versa) prevents their direct interpretation using traditional electrochemical methods. But when MCR-ALS is applied, voltammograms can be interpreted rather satisfactorily in both qualitative and quantitative terms. MCR-ALS showed the formation of Cd2Znbeta dom and Cd3Znalpha dom complexes when both metals were competitively added. A method based on the combined use of voltammetry and some chemometric techniques is proposed. It can be useful for the metal speciation of environmentally relevant natural ligands.

Construction of alpha-alpha domains structure in recombinant monkey metallothionein-1

The differences in metal-thiolate coordination and reactivity of mammalian metallothionein (MT) domains are closely related to their distinct, highly conservative cysteine number and position. Monkey metallothionein-1, containing a beta-domain with Cd(3)S(9) cluster and an alpha-domain with Cd(4)S(11) cluster, was used to evaluate the role of cysteine residues in the formation of MT's metal-thiolate clusters. The possible influence of cysteine residues on the binding and stability of MT domains has been examined with the metallothionein mutants: N4C, T27C and N4C/T27C, which possess ten or eleven cysteine residues in the re-constructed beta-domain, respectively. Assisted by study of UV, CD and electrospray ionization mass spectroscopy (ESI-MS) and their reactivity with DTNB (5,5'-dithiobis (2-nitrobenzoic acid)), we found that besides the original alpha-domain, some kinds of new domain containing 4-cadmium-thiolate clusters were formed in the N4C and N4C/T27C mutants of mkMT1. These new domains displayed metal binding and kinetic reactivity with DTNB similar to the alpha-domain. However, the thermal stability of the mutants was less stable than that of WT mkMT1. This might result from the disturbance of the inter-domains hydrogen bonds and of the non-cysteine amino acid residue arrangement.