THE MAE1 GENE OF SCHIZOSACCHAROMYCES-POMBE ENCODES A PERMEASE FOR MALATE AND OTHER C-4 DICARBOXYLIC-ACIDS

The mael gene of the yeast Schizosaccharomyces pombe was identified on the basis of its ability to complement a mutant defective in the tran sport of malic acid. Analysis of the DNA sequence revealed an open rea ding frame of 1314 base pairs, encoding a polypeptide of 438 amino aci ds with a predicted molecular weight of 49 kDa. A hydropathy profile o f the predicted amino acid sequence revealed a protein with ten membra ne-spanning or associated domains and hydrophilic N- and C- termini. T he predicted secondary structure of the protein is similar to models p roposed for other integral mambrane proteins from both prokaryotes and eukaryotes. The S. pombe mael gene encodes a single mRNA of 1.5 kb. T he mael gene is expressed constitutively and is not subject to catabol ite repression as was previously reported for the malate permease syst ems of Candida utilis and Hansenula anomala. The mael gene was mapped 2842 bp 5' to the MFml gene on chromosome I. Transport assays revealed that the mael gene encodes a permease involved in the uptake of L-mal ate, succinate and malonic acid. The sequence of the S. pombe mael gen e is available in GenBank under Accession Number U21002.