Absence of Qcr7 provokes destabilization of newly synthesized cytochrome b, which can be reversed by impairment of hemylation. (A) Mitochondrial translation products of the indicated strains were labeled with [³⁵S]-methionine. After 15 min, labeling was stopped by the addition of unlabeled methionine and the cells were incubated for 150 min. (B) The indicated strains were transformed with either empty plasmids or plasmids overexpressing CBP3 and CBP6 and the stability of mitochondrial translation products was analyzed after pulse-labeling with [³⁵S]-methionine. (C) Stability of mitochondrial translation products of the indicated cells were analyzed after 15 min of labeling. (D) The signals of cytochrome b or Var1 that remained after the 120-min chase were quantified. Mean values from three independent experiments ± SEM are shown. (E) Model of the fates of cytochrome b in the absence of Qcr7.