THE PICHIA-PASTORIS PER6 GENE-PRODUCT IS A PEROXISOMAL INTEGRAL MEMBRANE-PROTEIN ESSENTIAL FOR PEROXISOME BIOGENESIS AND HAS SEQUENCE SIMILARITY TO THE ZELLWEGER-SYNDROME PROTEIN PAF-1

We report the cloning of PER6, a gene essential for peroxisome biogene sis in the methylotrophic yeast Pichia pastoris. The PER6 sequence pre dicts that its product Per6p is a 52-kDa polypeptide with the cysteine -rich C3HC4 motif, Per6p has significant overall sequence similarity w ith the human peroxisome assembly factor PAF-1, a protein that is defe ctive in certain patients suffering from the peroxisomal disorder Zell weger syndrome, and with carl, a protein required for peroxisome bioge nesis and caryogamy in the filamentous fungus Podospora anserina, In a ddition, the C3HC4 motif and two of the three membrane-spanning segmen ts predicted for Per6p align with the C3HC4 motifs and the two membran e-spanning segments predicted for PAF-1 and carl, Like PAF-I, Per6p is a peroxisomal integral membrane protein. In methanol- or oleic acid-i nduced cells of per6 mutants, morphologically recognizable peroxisomes are absent, Instead, peroxisomal remnants are observed, In addition, peroxisomal matrix proteins are synthesized but located in the cytosol , The similarities between Per6p and PAL-I in amino acid sequence and biochemical properties, and between mutants defective in their respect ive genes, suggest that Per6p is the putative yeast homolog of PAF 1.