(A) Reaction mixtures containing wild-type mitochondria (WT mito) alone, wild-type cytosol (WT cyto) alone, or both were supplemented with [35S]cysteine (10 μCi), nucleotides (4 mM ATP, 1 mM GTP, 2 mM NADH and 1 mM NADPH), and ferrous ascorbate (10 μM). After incubation at 30°C for 30 min, samples were centrifuged, and the pellet (“P”; mitochondria) and supernatant (“S”; cytosol) fractions were analyzed by native PAGE and autoradiography. WT mito 1X = 50 μg of proteins; WT cyto = 300 μg of proteins.
(B) WT mitochondria (200 μg) alone were incubated with [35S]cysteine, nucleotides and iron. After centrifugation, the pellet and supernatant fractions were analyzed as in (A) above.
(C) Reaction mixtures containing different amounts of cytosol (1X = 50 μg) were supplemented with a fixed amount of mitochondria (200 μg), and incubated with [35S]cysteine, nucleotides and iron. Following centrifugation, samples were analyzed as in (A) above.