FIGURE 5.

Reduction in SSQ1 affects the induction of both the low and the high iron response without affecting cytosolic iron levels. Cells (Δssq1Δccc1) were transformed with plasmids containing a MET3-regulated SSQ1. The cells were also transformed with a GDO-expressing plasmid, a FET3-lacZ reporter construct, or a CCC1-lacZ reporter construct. Cells were grown overnight in CM without methionine to mid-log phase. Cells were harvested and placed in growth medium containing 100 μm FeSO₄ with or without 10× methionine for the specified times. Cells were homogenized, and β-galactosidase activity, GDO activity, aconitase activity, and cell protein were determined. A, FET3-lacZ. B, aconitase. C, GDO. D, CCC1-lacZ. The data are presented as specific activity, and the error bars reflect the S.D. of three independent experiments.