Regulation of
redox homeostasis in yeast.
Eleanor W. Trotter,
Chris M. Grant
Biomoecular Sciences, UMIST, Sackville Street, Manchester, M60 1QD, UK
(e.trotter@umist.ac.uk)
The glutathione (GSH)-glutaredoxin and thioredoxin systems play key roles in maintaining the redox homeostasis of the cell. Glutaredoxins and thioredoxins are small, structurally conserved, heat stable oxidoreductases. Oxidised thioredoxin is reduced directly by NADPH in a reaction catalysed by thioredoxin reductase (Trr1), whereas, glutaredoxins are reduced by glutathione (GSH), and oxidised glutathione (GSSG) is in turn reduced in an NADPH-dependent reaction catalysed by glutathione reductase (Glr1). Our studies show that there is an essential requirement for either a functional glutaredoxin or thioredoxin system. To understand the overlapping nature of these systems, we have focussed on glutathione reductase and thioredoxin reductase, since they are the key enzymes that determine the redox status of each system. Our studies show that Trr1 is required during normal cell growth whilst there is no apparent requirement for Glr1. In addition, we have found that the redox state of thioredoxins is maintained largely independently of the glutaredoxin system. In contrast, the redox state of glutaredoxins is strongly influenced by the redox state of thioredoxins. We suggest that independent redox regulation of thioredoxins enables cells to survive under conditions where the GSH/glutaredoxin system is oxidized. We will present our recent data regarding the roles of the thioredoxin and glutaredoxin systems in maintaining redox homeostasis in yeast during normal and stress conditions.