FIG 4 .

Cu targets cytosolic solvent-exposed Fe-S clusters. (A) Experimental setup for ⁵⁵Fe labeling experiments. Cells were grown for 16 h in Fe-poor SC medium with glucose and radiolabeled with 10 µCi ⁵⁵Fe for 1.5 h, CuSO₄ was added, and cells were grown in the presence of both ⁵⁵Fe and Cu for 1 h. (B) Wild-type (WT) S. cerevisiae cells were grown as described for panel A. Endogenous Leu1 protein was 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 = 8 (one-way repeated-measures ANOVA test, P < 0.0001). (C) WT cells transformed with vector overproducing Rli1-HA were grown as described for panel A and processed as described for panel B. n = 8 (P = 0.005).