Figure 2.

The ferredoxin Yah1p is required for normal activity of mitochondrial Fe/S proteins. (A) Depletion of Yah1p. Gal-YAH1 cells precultivated in galactose-containing medium or wild-type cells (WT) were grown for the indicated time periods in lactate medium containing 0.1% glucose at 30°C. After 24 h (arrow), cells were diluted 20-fold into fresh medium. Cell density was estimated from the OD at 600 nm. Mitochondria were isolated from Gal-YAH1 cells at the times indicated, and depletion of Yah1p was visualized by immunostaining (Upper). (B) The mitochondria described in A were used to measure the enzyme activities of several Fe/S cluster-containing proteins and of malate dehydrogenase (MDH) and citrate synthase (CS). The results are given relative to the activities measured for the mitochondrial enzymes of either wild-type or Gal-YAH1 cells grown in the presence of galactose. SDH, succinate dehydrogenase; Cyt c Red, cytochrome c reductase; Aco, aconitase. (C) Immunostaining of the indicated proteins with the mitochondria described in A. Aco1p, aconitase; Sdh2p, subunit 2 of complex II; Rieske, Rieske Fe/S protein; FeCh, ferrochelatase; cyt c₁, cytochrome c₁; Cox2p, subunit 2 of complex IV.