Yeast lacking Cu-Zn superoxide dismutase show altered iron homeostasis - Role of oxidative stress in iron metabolism

Saccharomyces cerervisiae lacking copper-zinc superoxide dismutase (sod1) s hows a series of defects, including reduced rates of aerobic growth in synt hetic glucose medium and reduced ability to grow by respiration in glycerol -rich medium. In this work, we observed that addition of iron improved the respiratory growth of the sod1 mutant and in glucose medium total intracell ular iron content was higher in the sod1 mutant than in wild type cells. Tr anscription of the high affinity iron transporter gene, FET3, was enhanced in the sod1 mutant, suggesting that iron transport systems were up-regulate d. An sod1/fet3 double mutant showed increased sensitivity to oxygen and in creased transcription of FET4, an alternative, low affinity, iron transport er. We propose that this increased iron demand in the sod1 mutant may be a reflection of the cells' efforts to reconstitute iron-sulfur cluster-contai ning enzymes that are continuously inactivated in conditions of excess supe roxide.