SYNTHESIS AND SUBCELLULAR LOCATION OF PEROXISOMAL MEMBRANE-PROTEINS IN A PEROXISOME-DEFICIENT MUTANT OF THE YEAST HANSENULA-POLYMORPHA

We have studied the synthesis and subcellular location of peroxisomal membrane proteins (PMPs) in cells of a peroxisome-deficient (per) muta nt of the methylotrophic yeast Hansenula polymorpha. Western blot anal ysis of methanol-induced cells of the per mutant, which had been growi ng in a continuous culture on a glucose/methanol mixture, indicated th at various PMPs were normally synthesized. As in wild type (WT) cells, the levels of PMP synthesis appeared to be dependent on specific cult ivation conditions, e.g. the carbon source used for growth. In contras t to WT controls, PMPs in methanol-induced per mutants were not subjec t to proteolytic degradation. Biochemical and immuno(cyto)chemical stu dies suggested that the PMPs in methanol-induced per cells were locate d in small proteinaceous aggregates, separated from peroxisomal matrix proteins that were also present in the cytosol. Vesicular membranous structures, resembling the morphology of intact peroxisomes, were neve r detected irrespective of the growth conditions employed.