The Peroxin Pex17p of the Yeast Yarrowia lipolytica Is Associated Peripherally with the Peroxisomal Membrane and Is Required for the Import of a Subset of Matrix Proteins

Abstract

PEX genes encode peroxins, which are required for the biogenesis of peroxisomes. The Yarrowia lipolytica PEX17 gene encodes the peroxin Pex17p, which is 671 amino acids in length and has a predicted molecular mass of 75,588 Da. Pex17p is peripherally associated with the peroxisomal membrane. The carboxyl-terminal tripeptide, Gly-Thr-Leu, of Pex17p is not necessary for its targeting to peroxisomes. Synthesis of Pex17p is low in cells grown in glucose-containing medium and increases after the cells are shifted to oleic acid-containing medium. Cells of the pex17-1 mutant, the original mutant strain, and the pex17-KA mutant, a strain in which most of the PEX17 gene is deleted, fail to form normal peroxisomes but instead contain numerous large, multimembraned structures. The import of peroxisomal matrix proteins in these mutants is selectively impaired. This selective import is not a function of the nature of the peroxisomal targeting signal. We suggest a regulatory role for Pex17p in the import of a subset of matrix proteins into peroxisomes.