Figure 1.

In vivo labeling of mitochondrial gene products in COX mutants. Wild-type (W303-1A) and mutant cells (described in Table I) were labeled with [³⁵S]methionine at 30°C for the indicated times in the presence of cycloheximide. One-half of each culture was incubated in the presence of 2 mg/ml chloramphenicol during the last 2 h of growth prior to labeling (+CAP). Samples were removed after the indicated times of labeling and processed as detailed in Materials and methods. The mitochondrial translation products are identified in the margin. Cox2p is not processed in ΔIMP1 and ΔIMP2 mutants. The Cox2p precursor (p) in these strains migrates slower that the mature Cox2p (m).