We intend to investigate the molecular mechanisms leading to the formation of maltase in S. cerevisae. We will define the nature of the regulatory system involved in maltase synthesis and the physical properties of the regulatory protein involved in the induction of maltase and maltose permease. We have recently shown that the MAL6 gene is a complex of four genes necessary for maltose fermentation: two regulatory genes(MAL63) and MAL64), the maltase structural gene(MAL62) and the maltose permease(MAL61). The MAL6 region has been cloned and the cloned genes will be used to identify and isolate the MAL63 and MAL64 regulatory proteins. Attempts will be made to reconstitute the system in vitro by studying the binding of the regulatory proteins to the cloned promotor. These studies of normal maltase synthesis will be complemented by genetic studies of mutants altered in maltase production. We shall isolate, using both classical mutagenesis and in vitro mutagenesis, mutants in all four genes of the mal6 locus and in their controlling sequences. This combination of biochemical and genetic approaches will allow a complete description of the regulation of maltase synthesis in S. cerevisae.
