Effects of Benzimidazole on the Oxygen‐Induced Biosynthesis of Hemoproteins in Yeast

Benzimidazole almost completely inhibited respiratory adaptation of yeast under conditions where total protein synthesis was only partially inhibited. The effects of benzimidazole on the synthesis of individual hemoproteins were examined. The production of enzymatically active cytochrome oxidase was almost totally blocked; this accounts for the interruption of respiratory adaptation. The biosynthesis of the NADH (and succinate): cytochrome c oxidoreductase segments, which include the cytochromes b and c1, was only partially inhibited. The induced synthesis of iso‐1‐cytochrome c displayed a singular insensitivity to the action of the drug. The mechanism of inhibition by benzimidazole appears to be different from that of cycloheximide and chloramphenicol.