The 3D structure of the metal complex contains two separate domains, alpha and beta. The alpha-domain encloses four bivalent metal ions in the form of a Me₄Cys₁₁ cluster. The beta-domain contains an analogous Me₃Cys₉ cluster. Monovalent metal ions like Cu(I) can form a cluster as well, via thiolate bonds. Much of our understanding of the biological actions of MTs has arisen from the comparative analysis of the chemical and structural features.

MT-1 is expressed in almost all tissues. It is a cytosolic protein, which is up-regulated in response to many factors, including metals, hormones, inflammation related stimuli (cytokines), and stressful reagents. It is suggested that it has multiple biological roles such as, regulatory role of Zn-metabolism (zinc-finger transcription factors), regulation of metal-exchange detoxification (marker for heavy metal intoxication), protection against reactive oxygen species (ROS), adaptation to stress, anti-apoptotic effects (activation of NF-κB/interaction with p50 subunit), and in protection against anticancer treatments. [2, 3]

The 3D structure of the metal complex contains two separate domains, alpha and beta. The alpha-domain encloses four bivalent metal ions in the form of a Me₄Cys₁₁ cluster. The beta-domain contains an analogous Me₃Cys₉ cluster. Monovalent ions like Cu(I) can form a cluster as well, via thiolate bonds. Much of our understanding of the biological actions of MTs has arisen from the comparative analysis of the chemical and structural features.

MT-2 is expressed in almost all tissues. It is a cytosolic protein, which is up-regulated in response to many factors, including metals, hormones, inflammation related stimuli (cytokines), and stressful reagents. It is suggested that it has multiple biological roles such as, regulatory role of Zn-metabolism (zinc-finger transcription factors), regulation of metal-exchange detoxification (marker for heavy metal intoxication), protection against reactive oxygen species (ROS), adaptation to stress, anti-apoptotic effects (activation of NF-κB/interaction with p50 subunit), and in protection against anticancer treatments. [2, 3]

The 3D structure of MT-3 with seven divalent metal ions seems to contain two separate domains (alpha and beta) with metal-thiolate clusters similar to those found in MT-1 and MT-2. The MT-3 contains one redox labile zinc ion, which is proposed to have a certain impact to its biological function. In order to keep all 7 zinc ions bound; the product is supplied in the presence of 1mM DTT as a reducing reagent.

MT-3 is a non-inducible protein primarily confined to the brain. It impairs the survival and neurite formation of cultured neurons. MT-3 was found to be deficient in the brain of Alzheimer’s disease patients and therefore exhibits biological activity different from that of MT-1 and MT-2.