Abstract. We have been characterizing the peroxisomal membrane proteins of the methylo-trophic yeast Candida boidinii and their importance to the structure, assembly and function of the organelle. The association of newly synthesized PMP20, a peripheral membrane protein, with peroxisomes was much more rapid than that of the matrix enzymes in pulse-chase experiments. During proliferation of peroxisomes on metha-nol, the synthesis of the peroxisomal membranes and of the integral membrane protein PMP47 preceded synthesis of PMP20 and the major matrix enzymes, alcohol oxidase and dihydroxyacetone synthase. While PMP20 appears to be specific for methanol metabolism, PMP47 and two other integral membrane proteins, PMP32 and PMP31, were abundant components of the peroxisomal membranes when the organelle was induced to proliferate by other growth substrates. Genes encoding PMP20, PMP31 and PMP47 have been isolated, and PMP47 has been expressed in Saccharomyces cerevisiae, where it sorts to the peroxisomes and assembles into the membrane with the endogenous membrane proteins. Preliminary results indicate that PMP47 contains a novel, but presently undefined, sorting signal. The importance of the peroxisomal membrane proteins for peroxisomal biogenesis and function are discussed.
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