Biogenesis of the cytochrome bc 1 complex in isolated rat hepatocytes

Abstract

Isolated rat hepatocytes were labeled with [ 35S]methionine in the absence or presence of cycloheximide or chloramphenicol. The cytochrome bc 1 complex was isolated from labeled cells by a micromethod and analyzed by SDS-polyacrylamide gel electrophoresis and fluorography. All subunits except the two smallest, subunits VII and VIII, were labeled in the absence of translational inhibitors. In the presence of cycloheximide only subunit III (molecular weight, 30 000) was labeled. This polypeptide, identified as an apo-cytochrome b, was weakly labeled with [ 35S]methionine in the presence of cycloheximide, indicating a strict dependence of cytoplasmically synthesized products for its assembly. In the presence of chloramphenicol, labeling was inhibited only in subunit III.