metallothioneeins

Metallothioneins are a family of low molecular weight, cysteine-rich proteins found in the tissues of vertebrates, invertebrates, and plants. Their primary function is to bind and sequester metal ions, particularly heavy metals like cadmium, mercury, zinc, and copper. This binding capability makes them crucial in metal detoxification and homeostasis, protecting cells from the toxic effects of excessive metal accumulation.

The structure of metallothioneins is characterized by a high proportion of cysteine residues, which form a significant number of metal-binding sites. These cysteine residues can coordinate with metal ions through their thiol groups. The specific metal ions bound can influence the protein's tertiary structure.

Metallothioneins play a role in essential physiological processes involving zinc and copper metabolism. They can store these metals and release them when cellular demand arises, thus maintaining cellular metal balance. In response to metal exposure or oxidative stress, the synthesis of metallothioneins is upregulated, providing a protective mechanism.

The study of metallothioneins has implications in various fields, including toxicology, environmental science, and medicine. Their ability to bind heavy metals makes them potential biomarkers for metal exposure and candidates for therapeutic interventions in metal poisoning. Different isoforms of metallothioneins exist, with varying affinities for different metal ions and distinct tissue distribution.