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Replacement of a conserved tyrosine by tryptophan in Gal3p of Saccharomyces cerevisiae reduces constitutive activity: implications for signal transduction in the GAL regulon

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Title Replacement of a conserved tyrosine by tryptophan in Gal3p of Saccharomyces cerevisiae reduces constitutive activity: implications for signal transduction in the GAL regulon
 
Creator LAKSHMINARASIMHAN, A
BHAT, P
 
Subject gal4p-activated genes
galactose
protein
yeast
galactokinase
transcription
mechanism
pathway
switch
activation
ghmp kinases
signal transduction
fine regulation
galactose recognition
conserved tyrosine
 
Description The ability of Saccharomyces cerevisiae to utilize galactose is regulated by the nucleo-cytoplasmic shuttling of a transcriptional repressor, the Gal80 protein. Gal80 interacts with the transcriptional activator Gal4 in the nucleus and inhibits its function, preventing induction of the GAL genes. In response to galactose, the relative amounts of Gal80 in the cytoplasm and the nucleus are modulated by the action of a signal transducer, Gal3. Although it has been speculated that Gal3 binds galactose, this has not been experimentally demonstrated. In this study, we show that replacement of a conserved tyrosine in Gal3 by tryptophan leads to a reduction of its constitutive activity in the absence of galactose. In addition, this mutant protein was fully functional in vivo only when high concentrations of galactose were present in the medium. When overexpressed, the mutant was found to activate the genes GAL1 and GAL7/10 differentially. The implications of these findings for the fine regulation of GAL genes, and its physiological significance, are discussed.
 
Publisher SPRINGER
 
Date 2011-08-29T17:52:23Z
2011-12-26T12:58:42Z
2011-12-27T05:49:05Z
2011-08-29T17:52:23Z
2011-12-26T12:58:42Z
2011-12-27T05:49:05Z
2005
 
Type Article
 
Identifier MOLECULAR GENETICS AND GENOMICS, 274(4), 384-393
1617-4615
http://dx.doi.org/10.1007/s00438-005-0031-6
http://dspace.library.iitb.ac.in/xmlui/handle/10054/12151
http://hdl.handle.net/10054/12151
 
Language en