Metallotioneiner

Metallothioneins are a family of low molecular weight, cysteine-rich proteins found in the tissues of vertebrates, invertebrates, and plants. They are characterized by their high affinity for and ability to bind a variety of metal ions, particularly zinc, copper, cadmium, and mercury. This metal-binding capacity is due to the abundance of sulfhydryl groups present in the cysteine residues, which form coordinate bonds with the metal ions.

The primary functions of metallothioneins are believed to be related to metal homeostasis and detoxification. They play a crucial role in the storage and transport of essential trace metals like zinc and copper, ensuring their availability for cellular processes while preventing their toxic accumulation. In the case of heavy metal exposure, metallothioneins act as a protective mechanism by sequestering these toxic metals, thereby preventing them from interacting with other cellular components and causing damage.

Metallothioneins are also implicated in cellular defense against oxidative stress. Their ability to bind reactive oxygen species and their metal-binding properties contribute to scavenging free radicals and protecting cells from oxidative damage. The expression of metallothionein genes can be induced by various stimuli, including exposure to heavy metals, glucocorticoids, and inflammatory cytokines, reflecting their dynamic role in cellular adaptation and protection. Different isoforms of metallothioneins exist, with variations in their amino acid sequence and metal-binding preferences, contributing to specialized functions within different tissues and cellular compartments.