Metal-specific synthesis of two metallothioneins and gamma-glutamyl peptides in Candida glabrata.

Abstract

Cellular resistance to heavy metal cytotoxocity in most species is mediated by the binding of metal ions either ti a cysteine-rich polypeptide in the metallothionein family or to short cysteine-containing .gamma.-glutamyl peptides. One of these metal binding systems has been found in most organisms studied. However, the yeast Candida (Torulopsis) glabrata expresses both metallothionein and the .gamma.-glutamyl peptides for metal detoxification, and each system is regulated in a metal-specific manner. Exposure of C. glabrata to copper salts stimulates formation of two metallothionein-like polypeptides with a cysteine content of 30 mol% and the repeated sequence Cys-Xaa-Cys. The cells synthesize .gamma.-glutamyl peptides upon exposure to cadmium salts. Penta- and tetrapeptides that form a cadmium-thiolate cluster in a peptide oligomer containing labile sulfur are synthesized.