coa3Δ and cox14Δ yeast cells display increased COX1 expression and reduced stability of Cox1. (A) In vivo labeling of mitochondrial translation products was performed according to Materials and methods. After 5-min pulse, cells were lysed and subjected to TCA precipitation, and labeled proteins were analyzed by SDS-PAGE and digital autoradiography. (B) Three independent experiments as in A were quantified using ImageQuant TL software (GE Healthcare). Values represent the mean ratios of Cox1/Var1, relative to wild type (WT; 100%). Error bars indicate SEM (n = 3). (C) In vivo labeling of mitochondrial translation products was performed as in A. After 5-min pulse, translations were stopped by the addition of excess unlabeled methionine and chloramphenicol. Samples were taken after 5-, 15-, and 45-min chase and analyzed as in A. (D) Four independent experiments as in C were quantified using ImageQuant TL software, and Cox1 signals were plotted against chase times. Values represent mean ratios of Cox1/Cob, relative to 0-min chase (100%). Error bars indicate SEM (n = 4).