Pay32p of the yeast Yarrowia lipolytica is an intraperoxisomal component of the matrix protein translocation machinery.

Pay mutants of the yeast Yarrowia lipolytica fail to assemble functional peroxisomes. One mutant strain, pay32-1, has abnormally small peroxisomes that are often found in clusters surrounded by membraneous material. The functionally complementing gene PAY32 encodes a protein, Pay32p, of 598 amino acids (66,733 D) that is a member of the tetratricopeptide repeat family. Pay32p is intraperoxisomal. In wild-type peroxisomes, Pay32p is associated primarily with the inner surface of the peroxisomal membrane, but approximately 30% of Pay32p is localized to the peroxisomal matrix. The majority of Pay32p in the matrix is complexed with two polypeptides of 62 and 64 kD recognized by antibodies to SKL (peroxisomal targeting signal-1). In contrast, in peroxisomes of the pay32-1 mutant, Pay32p is localized exclusively to the matrix and forms no complex. Biochemical characterization of the mutants pay32-1 and pay32-KO (a PAY32 gene disruption strain) showed that Pay32p is a component of the peroxisomal translocation machinery. Mutations in the PAY32 gene prevent the translocation of most peroxisome-bound proteins into the peroxisomal matrix. These proteins, including the 62-kD anti-SKL-reactive polypeptide, are trapped in the peroxisomal membrane at an intermediate stage of translocation in pay32 mutants. Our results suggest that there are at least two distinct translocation machineries involved in the import of proteins into peroxisomes.