ABSTRACT
This chapter focuses on intracellular copper sequestration by metallothionein (MT), although glutathione (GSH)-related isopeptides and sulfide also act in copper sequestration in certain species. Regulation of sequestering molecules is important for homeostatic control of the intracellular copper concentration. The identification of metallothionein as an important molecule in copper buffering emerged from early studies on the adaptation of yeast to over come the toxic effects of copper. MT genes display a high basal level of expression, and it is reasonable to expect that other factors may promote transcription. Methylation has been noted to be important in the expression of MT genes in mammalian cells. The characteristics of metallothionein, the structure of its gene, and its expression have all offered intriguing possibilities for yeast biotechnologists to exploit. Metallothionein promoters have been popular in mammalian cell expression, and they are just as useful for driving expression of foreign genes in yeast, because of their convenient and rapid response to copper ions.
