THE TARGETING INFORMATION OF THE MITOCHONDRIAL OUTER-MEMBRANE ISOFORM OF CYTOCHROME B(5) IS CONTAINED WITHIN THE CARBOXYL-TERMINAL REGION

Two isoforms of mammalian cytochrome b(5), which have homologous cytosolic amino-terminal catalytic domains, are located one on endoplasmic reticulum (ER b(5)) the other on mitochondrial outer membranes (OM b(5)), A cDNA coding for the previously unknown carboxyl-terminal domain of OM b(5) was cloned and a chimera between the catalytic domain of ER b(5) and the carboxyl-terminal region of OM b(5) was expressed in cultured mammlian cells. The chimera localized to mitochondria, indicating that the carboxyl-terminal 43 amino acids of OM b(5) contain sufficient information to target the catalytic domain of ER b(5) to the mitochondrial outer membrane.