Synthesis of proteolipid protein by yeast mitochondria

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Extracted proteolipid protein accounts for up to 3% of total yeast mitochondrial protein. The incorporation of label from 14C-leucine into proteolipid by isolated mitochondria is inhibited by erythromycin and mikamycin, specific inhibitors of protein synthesis by mitochondrial ribosomes, and not by the cytoplasmic ribosomal inhibitor, cycloheximide; it appears completely stable to a puromycin chase which solubilizes about 40% of total mitochondrial label. The exact proportion of the label incorporated into proteolipid, ranging from 20 to 40% of that in completed polypeptides, is dependent upon the growth phase of the yeast cells. It is concluded that the protein of proteolipid is a major product of the mitochondrial system of protein synthesis in S. cerevisiae, but not the sole product.