H. Liu et al., PER3, A GENE REQUIRED FOR PEROXISOME BIOGENESIS IN PICHIA-PASTORIS, ENCODES A PEROXISOMAL MEMBRANE-PROTEIN INVOLVED IN PROTEIN IMPORT, The Journal of biological chemistry, 270(18), 1995, pp. 10940-10951
PER genes are essential for the biogenesis of peroxisomes in the yeast
Pichia pastoris. Here we describe the cloning of PER3 and functional
characterization of its product Per3p. The PER3 sequence predicts that
Per3p is a 713-amino acid (81-kDa) hydrophobic protein with at least
three potential membrane-spanning domains. We show that Per3p is a mem
brane protein of the peroxisome. Methanol- or oleate-induced cells of
per3-1, a mutant strain generated by chemical mutagenesis, lack normal
peroxisomes but contain numerous abnormal vesicular structures. The v
esicles contain thiolase, a PTS2 protein, but only a small portion of
several other peroxisomal enzymes, including heterologously expressed
luciferase, a PTS1 protein. These results suggest that the vesicles in
per3-1 cells are peroxisomal remnants similar to those observed in ce
lls of patients with the peroxisomal disorder Zellweger syndrome, and
that the mutant is deficient in PTS1 but not PTS2 import. In a strain
in which most of PER3 was deleted, peroxisomes as well as peroxisomal
remnants appeared to be completely absent, and both PTS1- and PTS2-con
taining enzymes were located in the cytosol. We propose that Per3p is
an essential component of the machinery re quired for import of all pe
roxisomal matrix proteins and is composed of independent domains invol
ved in the import of specific PTS groups.