THE IN-VITRO PERMEABILITY OF YEAST PEROXISOMAL MEMBRANES IS CAUSED BYA 31 KDA INTEGRAL MEMBRANE-PROTEIN

A major 31 kDa integral peroxisomal membrane protein (PMP31) of Hansen ula polymorpha was purified to homogeneity from isolated peroxisomal m embranes by FPLC after solubilization by Triton X-100. Biochemical ana lysis indicated that this protein, which showed cross-reactivity with antibodies against the 31 kDa porin of the mitochondrial outer membran e of Saccharomyces cerevisiae, had pore-forming properties. Firstly, p roteoliposomes composed of asolectin and purified PMP31 showed selecti ve permeability, determined as the C-14!sucrose/H-3!dextran leakage ratios. Furthermore, the generation of a DELTAPSI by potassium diffusi on gradients was negatively affected by the presence of PMP31 in asole ctin liposomes. A similar effect was observed in proteoliposomes conta ining purified cytochrome c oxidase as a DELTAPSI generating system. C ontrol experiments confirmed that the observed leakage is significant and introduced by the incorporation of PMP31 protein. Selective sucros e leakage was abolished in samples pretreated with glutaraldehyde; an identical effect of glutaraldehyde was, however, not observed for the membrane potential measurements.