The metallothionein/thionein system: an oxidoreductive metabolic zinc link.

Metallothioneins (MTs) were discovered more than 50 years ago and identified as low-molecular weight, sulfhydryl-rich proteins that were subsequently found to bind zinc predominantly. The binding of seemingly redox inactive zinc ions allows MT to play a central role in oxidoreductive cellular metabolism, cellular zinc distribution and homeostasis. In this interpretive study, we discuss the interaction of MT with physiologically relevant molecules and its effect on zinc-thiolate bonds. These interactions are linked to recent progress in the functional role of MT in cellular zinc transport, energy production, and protection of the organism against oxidative stress and neurodegenerative diseases.