THE PAS8 MUTANT OF PICHIA-PASTORIS EXHIBITS THE PEROXISOMAL PROTEIN IMPORT DEFICIENCIES OF ZELLWEGER SYNDROME CELLS - THE PAS8 PROTEIN BINDS TO THE COOH-TERMINAL TRIPEPTIDE PEROXISOMAL TARGETING SIGNAL, AND ISA MEMBER OF THE TPR PROTEIN FAMILY

We previously described the isolation of mutants of the yeast Pichia p astoris that are deficient in peroxisome assembly (pas mutants). We de scribe the characterization of one of these mutants, pas8, and the clo ning of the PAS8 gene. The pas8 mutant is deficient for growth, but no t for division or segregation of peroxisomes, or for induction of pero xisomal proteins. Two distinct peroxisomal targeting signals, PTS1 and PTS2, have been identified that are sufficient to direct proteins to the peroxisomal matrix. We show that the pas8 mutant is deficient in t he import of proteins with the PTS1, but not the PTS2, targeting signa l. This is the same import deficiency as that found in cells from pati ents with the lethal human peroxisomal disorder Zellweger syndrome. Cl oning and sequencing of the PAS8 gene reveals that it is a novel membe r of the tetratricopeptide repeat gene family. Antibodies raised again st bacterially expressed PAS8 are used to show that PAS8 is a peroxiso mal, membrane-associated protein. Also, we have found that in vitro tr anslated PAS8 protein is capable of binding the Ml targeting signal sp ecifically, raising the possibility that PAS8 is a PTS1 receptor.