Molecular and General Genetics MGG

, Volume 135, Issue 3, pp 203–212 | Cite as

Studies on the positive regulatory gene, GAL4, in regulation of galactose catabolic enzymes in Saccharomyces cerevisiae

  • Amar J. S. Klar
  • Harlyn O. Halvorson


Studies were undertaken to elucidate the role of the GAL4 locus in regulating the galactose catabolic enzymes in Saccharomyces cerevisiae. The GAL4 locus has been proposed to have a regulatory function since GAL4 mutants are pleiotropic, lacking epimerase, galactokinase, transferase and galactose permease activities. This pleiotropic effect could be explained if the GAL4 gene codes for a peptide required for above enzyme activities. To study if the GAL4 gene codes for a structural component of the above enzymes, a temperature sensitive mutation mapping close to or within the GAL4 gene (gal4-1ts) was isolated. The results suggest that the GAL4 locus does not code for a polypeptide common to the transferase, epimerase, galactokinase, and permease enzymes since these enzymes extracted from the gal4-1ts mutant did not differ qualitatively in thermolability and temperature optima from those of the wild-type. It was found that in the gal4-1ts mutant the synthesis of the epimerase is temperature sensitive and that the GAL4 gene product does not have any effect on the in vivo stability of epimerase.


Enzyme Peptide Polypeptide Galactose Saccharomyces Cerevisiae 
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Copyright information

© Springer-Verlag 1974

Authors and Affiliations

  • Amar J. S. Klar
    • 1
  • Harlyn O. Halvorson
    • 1
  1. 1.Department of Biology and Rosenstiel Basic Medical Sciences Research CenterBrandeis UniversityWaltham

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