The GAL4 protein of Saccharomyces cerevisiae and the LAC9 protein of Kluyveromyces lactis are transcription activator proteins with similar structure and function. Greatest similarity occurs in the C region near the carboxy terminus, where 16 of 18 amino acids are identical. The function of the C region is unclear. Here we show that the structural similarity is reflected in functional similarity. Single amino acid changes in the C region of GAL4 and LAC9 create a similar phenotype: constitutive gene expression. In S. cerevisiae the constitutive phenotype caused by GAL4 mutants can be abolished by overproduction of GAL80. These results support a model in which the C region of GAL4 and LAC9 constitute similar negative regulatory domains that interact with GAL80 in S. cerevisiae and an unidentified GAL80 homolog in K. lactis. This protein-protein interaction prevents expression of the galactose operon in the uninduced state.
|Number of pages||5|
|Journal||Nucleic Acids Research|
|State||Published - Sep 11 1990|
Bibliographical noteFunding Information:
We thank Michael M.Witte and Susan Stormzand-Murphy for initial experiments using LAC9. This research was supported by Public Health Service grant GM-22749 from the National Institutes of Health and by Biomedical Research Support Grant RR05374 from the Biomedical Research Support Branch, Division of Research Facilities and Resources, National Institutes of Health.
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