PAY4, A GENE REQUIRED FOR PEROXISOME ASSEMBLY IN THE YEAST YARROWIA-LIPOLYTICA, ENCODES A NOVEL MEMBER OF A FAMILY OF PUTATIVE ATPASES

PAY genes are required for peroxisome assembly in the yeast Yarrowia l ipolytica. Here we characterize one mutant, pay4, and describe the clo ning and sequencing of the PAY4 gene. The pay4 mutant shows no identif iable peroxisomes by biochemical and morphological criteria. The compl ementing PAY4 gene encodes a polypeptide, Pay4p, 1025 amino acids in l ength and having a predicted molecular mass of 112,258 Da. The predict ed Pay4p sequence contains two putative ATP-binding domains and shows structural relationships to other potential ATP-binding proteins invol ved in biological processes as diverse as peroxisome biogenesis, vesic le-mediated protein transport, cell cycle control, and transcriptional regulation. These proteins all share a highly conserved stretch of ap proximately 175 amino acids that contains a consensus sequence for ATP binding. Pay4p shows sequence conservation with Pas1p and Pas5p, puta tive ATPases required for peroxisomal assembly in the yeasts Saccharom yces cerevisiae and Pichia pastoris, respectively. Pay4p, Pas1p, and P as5p are presumably related members of a family of putative ATPases in volved in peroxisome biogenesis. Pay4p is synthesized in low amounts i n Y lipolytica cells grown in glucose, and there is a rapid and pronou nced increase in the levels of Pay4p upon transfer of the cells to a m edium containing oleic acid as the sole carbon source.