Oxidative dimerization in metallothionein is a result of intermolecular disulphide bonds between cysteines in the α-domain

Abstract

Upon storage under aerobic conditions metallothioneins (MTs) form a new species, which is characterized by a molecular mass approximately twice the size of monomeric MT and shifted (113/111)Cd- and (1)H-NMR resonances. The investigation of this oxidative dimerization process by NMR spectroscopy allowed us to structurally characterize this MT species that has been described to occur in vivo and might be synthesized under conditions of oxidative stress. The oxidative dimer was characterized by the formation of an intermolecular cysteine disulphide bond involving the alpha-domain, and a detailed analysis of chemical shift changes and intermolecular nuclear Overhauser effects points towards a disulphide bond involving Cys(36). In contrast to the metal-bridged (non-oxidative) dimerization, the metal-cysteine cluster structures in both MT domains remain intact and no conformational exchange or metal-metal exchange was observed. Also in contrast to the many recently reported oxidative processes which involve the beta-domain cysteine groups and result in the increased dynamics of the bound metal ions in this N-terminal domain, we found no evidence for any increased dynamics in the alpha-domain metals following this oxidation. Therefore these findings provide additional corroboration that metal binding in the C-terminal alpha-domain is rather tight, even under conditions of a changing cellular oxidation potential, compared with the more labile/dynamic nature of the metals in the N-terminal beta-domain cluster under similar conditions.

Role of metallothioneins in benign and malignant thyroid lesions

“…In the overall structure of MTs two domains have been recognized, the domain α and β [23]. The domain α comprises amino acids 31-68 and is located on the C-terminal edge, whereas the N-terminal domain β comprises amino acids 1-30 [20].…”

Metallothionein‐I+II in neuroprotection

“…Metal/thiolate stochiometries depend mainly on metal coordination properties; for divalent metals, the a-and b-domains coordinate four and three ions in a tetrahedral manner, respectively [1]. Furthermore, the impact of cellular oxidative and nitrosative status on metal saturation and MT poly-/dimerization (through the formation of intra-and intermolecular disulfide bonds) place redox status as yet another variable affecting MT structure [5][6][7]. Furthermore, the impact of cellular oxidative and nitrosative status on metal saturation and MT poly-/dimerization (through the formation of intra-and intermolecular disulfide bonds) place redox status as yet another variable affecting MT structure [5][6][7].…”

Fish and molluscan metallothioneins

“…Metal bridge dimerization is reversed by dilution or addition of chelating agents, whereas oxidative dimers are reduced by reducing compounds [8]. As reported previously [9], oxidative dimerization may also occur in vivo under conditions of stress, such as exposure to toxic metals and reactive oxygen species and in neurological disorders (e.g. Alzheimer's disease).…”