Heme a induces assembly of rat liver cytochrome c oxidase subunits I‐III in isolated mitochondria

Abstract The assembly of cytochrome c oxidase subunits I-III was studied in vitro in isolated rat liver mitochondria pre-labeled with [ 35 S]methionine. Individual subunits were immunoabsorbed with monospecific antibodies. Isolated heme a from rat liver mitochondria, when added to radiolabeled mitochondria, induced assembly of subunit I with subunits II and III. Assembly of these subunits was not observed in mitochondria incubated in the presence of heme b (hemin) or in the absence of heme. Quantitative analysis of immunoabsorbed, radiolabeled subunits suggests that the predominant effect of heme a is on the assembly of subunit I with subunit III. Cytochrome oxidase assembly Heme a requirement (Rat liver mitochondria)