Metallothioneins and zinc: their functions and interactions.

The impact of environmental and occupational contamination on living organisms has been an interesting topic for scientific and lay public for a long time. The synthesis of metallothioneins is one of the protection strategies, by which organisms protect themselves from metal-induced toxicity. There are four known isoforms of metallothioneins. This article summarizes the role of the widely expressed mammalian metallothionein-1 and metallothionein-2 isoforms in zinc homeostasis, apoptosis, and as novel potential marker of ageing. The metallothionein-3 and metallothionein-4 have been discovered to possess distinct functional properties. The properties of metallothioneins and their interplay are likely to be essential for the still elusive biological function of these proteins. (Ref. 49.).