Role of the glutathione/glutaredoxin and thioredoxin systems in yeast growth and response to stress conditions

Sulphydryl groups (-SH) play a remarkably broad range of roles in the cell, and the redox status of cysteine residues can affect both the structure an d the function of numerous enzymes, receptors and transcription factors. Th e intracellular milieu is usually a reducing environment as a result of hig h concentrations of the low-molecular-weight thiol glutathione (GSH). Howev er, reactive oxygen species (ROS), which are the products of normal aerobic metabolism, as well as naturally occurring free radical-generating compoun ds, can alter this redox balance. A number of cellular factors have been im plicated in the regulation of redox homeostasis, including the glutathione/ glutaredoxin and thioredoxin systems. Glutaredoxins and thioredoxins are ub iquitous small heat-stable oxidoreductases that have proposed functions in many cellular processes, including deoxyribonucleotide synthesis, repair of oxidatively damaged proteins, protein folding and sulphur metabolism. This review describes recent findings in the lower eukaryote Saccharomyces cere visiae that are leading to a better understanding of their role in redox ho meostasis in eukaryotic cell metabolism.