Biosynthesis of metal-binding polypeptides and their precursors in response to cadmium in Datura innoxia

摘要

Metal-tolerant Datura innoxia cells synthesize large amounts of a class of metal-binding polypeptides, poly((gamma)-glutamylcysteinyl) glycines (((gamma)-EC)(sub n)G, n=2-5), when exposed to Cd. These polypeptides have a high affinity for Cd (2) and certain other metal ions and are thought to play a role in metal tolerance in higher plants. ((gamma)-EC)(sub n)G is biosynthetically derived from glutathione. Therefore, the response of Datura cells to Cd must include an increase in production of glutathione and its precursors, since cells rapidly accumulate very high concentrations of these metal-binding polypeptides. The biosynthesis of ((gamma)-EC)(sub n)Gs, glutathione, and cysteine in response to Cd exposure is described. The physiological significance of the synthesis of these polypeptides and their precursors and its relevance to Cd tolerance and metal homeostasis are discussed. 34 refs., 6 figs., 1 tab.