Redox Sensor Function of Metallothioneins

Publisher Summary This chapter describes contemporary approaches to assess the redox status of Metallothionein (MT) cysteines and their relationship to MT metal sequestration and release. The redox conversions of MT cysteines are likely to be the principal mechanisms for regulation of metal binding and release by this protein. Oxidative and/or nitrosafive challenges can serve to promote metal ion release from MT to render their delivery to specific target proteins. It is tempting to consider the potential roles of MTs as redox sensors because of their high sensitivity to cysteine modification, as well as their potential to amplify signals by releasing multiple metal ions. In other words, MTs may act early in a biological signaling cascade that triggers metal-dependent biochemical and cellular responses. Alternatively, uncontrolled release of metals by excessive oxidative stress may contribute to metal toxicity. Because oxidative and nitrosative signaling is ubiquitous within cells, the physiological function of MT demands that efficient recycling of modified cysteines be operative. Little is known regarding the potential mechanisms for the regeneration of MT after oxidative/nitrosative modification, but they may involve endogenous dithiols, such as thioredoxin, and pharmacologically relevant dithiols, such as dihydrolipoate.