Proton ionophores prevent assembly of a peroxisomal protein.

Peroxisomal matrix proteins are imported into the organelle posttranslationally. Here we report that proton ionophores disrupt the import and assembly of alcohol oxidase, a homo-octameric flavoprotein of the induced peroxisome from the methylotrophic yeast Candida boidinii. When drug is added to cells containing newly synthesized monomeric alcohol oxidase, octamerization fails to occur and a membrane-associated complex is formed instead. The formation of the complex, which appears to face the cytoplasmic side of the membrane, is reversed when drug is removed, leading to the generation of octamer. Surprisingly, when drug is added to cells containing newly assembled octamers, they dissociate into monomers. We suggest that both the complex and the labile octamer are intermediates in the normal assembly pathway of alcohol oxidase and that energy is required for import and maturation of this peroxisomal protein.