The organization and transcription of the galactose gene cluster of Kluyveromyces lactis.

The yeast Kluyveromyces lactis grows on galactose by inducing the Leloir pathway enzymes-kinase, epimerase, and transferase. To investigate the molecular mechanism for regulating expression of this metabolic pathway we isolated GAL1, GAL7, GAL10, which code for kinase, transferase, and epimerase, respectively, and characterized their size, organization, and transcriptional regulation. Our results indicate that induction of the Leloir pathway in K. lactis occurs at the level of transcription and that the organization and regulation of the GAL gene cluster in K. lactis is closely related to the homologous gene cluster in Saccharomyces cerevisiae. Likewise, the Upstream Activator Sequences that regulate induction of the GAL genes are similar in base sequence, number and relative location in the two yeasts.