FIG 5 .

Critical targets for Cu toxicity are Fe-S clusters of proteins with functions in the CIA machinery and iron regulon activation. (A to D) WT S. cerevisiae cells (A), WT cells transformed with vector overproducing Nbp35-TAP (B) or Nar1-3HA (C), and WT cells in which the GRX4 gene was genomically tagged with the HA epitope (D) were grown as described for Fig. 4A. The overproduced Nbp35-TAP and Nar1-3HA or endogenous Dre2 and Grx4-HA proteins were immunoprecipitated from cell extracts with specific antibodies. The amount of coprecipitated ⁵⁵Fe was quantified by scintillation counting. Data are presented relative to the values obtained for samples not treated with Cu. n = 6 for Nar1 and n = 8 for the remaining proteins (one-way repeated-measures ANOVA test, P < 0.0001 for Dre2, Nbp35, Nar1, and Grx4).