Yeast metallothionein and applications in biotechnology.


The metal-regulated genetic system in yeasts offers a powerful new tool which has not been exploited in the past. Metal-regulated DNA sequences are the most efficient elements for heterologous expression discovered to date. The information on yeast metallothionein (MT) brought together in this review should be useful to the geneticist, the biochemist, and the pharmacologist as well as to the inorganic chemist. Living organisms have evolved several mechanisms to respond to toxic effects of heavy metals. One of the most common mechanisms is the induction of MTs after uptake of the metal into the cell. MTs are broadly defined as a class of low-molecular-weight cysteine-rich proteins which bind heavy metals (42). MTs are widely distributed throughout living organisms and are fairly well conserved in humans, mammals, plants, and fungi (23, 42). A unique property of this class of proteins is their inducibility in response to the treatment of cells with appropriate metals. For example, resistartce to the toxic effects of copper ions in the yeast Saccharomyces cerevisiae is mediated by induction of a 6573-dalton cysteine-rich protein, copper-MT (Cu-MT) (9, 21). In the past few years, with the advent of recombinant deoxyribonucleic acid (DNA) technology, the field of yeast genetics has taken a new turn. Availability of a variety of mutants, defined and mapped by genetic techniques, coupled


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