Genetic mapping and biochemical analysis of mutants in the maltose regulatory gene of the MAL1 locus of Saccharomyces cerevisiae.

The MAL1 locus of Saccharomyces cerevisiae comprises three genes necessary for maltose utilization: a regulatory (MALR), a maltose transport (MALT) and a maltase gene (MALS). A fine structure genetic map of the MAL1R gene was constructed and the order of mutations was confirmed by plasmid-mediated chromosomal recombination. The mutations cluster non-randomly within the 5' half of the gene, where the putative DNA binding domain of the encoded protein is located. Only mutations mal1R-22 and MAL1R-72 map in the 3' terminal half of the gene; these mutations cause a different pattern of transcriptional regulation of plasmid-borne MAL6T genes. Experiments supporting a direct involvement of the MALR-encoded protein in carbon catabolite repression of MAL gene expression are reported.