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  • 1
    ISSN: 1432-072X
    Keywords: Key words Trehalase ; Trehalose ; Kluyveromyces lactis ; Protein phosphorylation ; NTH1 ; Glucose induction ; Glucose transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We cloned the Kluyveromyces lactis KlNTH1 gene, which encodes neutral trehalase. It showed 65.2% and 68.5% identity at nucleotide and amino acid sequence level, respectively, with the Saccharomyces cerevisiae NTH1 gene. Multiple alignment of the predicted trehalase protein sequences from yeasts, bacteria, insects, and mammals revealed two major domains of conservation. Only the yeast trehalases displayed in an N-terminal extension two consensus sites for cAMP-dependent protein phosphorylation and a putative Ca2+-binding sequence. Gene disruption of the KlNTH1 gene abolished neutral trehalase activity and clearly revealed a trehalase activity with an acid pH optimum. It also resulted in a high constitutive trehalose level. Expression of the KlNTH1 gene in an S. cerevisiae nth1Δ mutant resulted in rapid activation of the heterologous trehalase upon addition of glucose to cells growing on a nonfermentable carbon source and upon addition of a nitrogen source to cells starved for nitrogen in a glucose-containing medium. In K. lactis, the same responses were observed except that rapid activation by glucose was observed only in early-exponential-phase cells. Inactivation of K. lactis neutral trehalase by alkaline phosphatase and activation by cAMP in cell extracts are consistent with control of the enzyme by cAMP-dependent protein phosphorylation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Key words Trehalose synthase complex ; Stress-responsive element (STRE) ; Stress response ; Nutrients ; Ras-cAMP pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Saccharomyces cerevisiae cells show under suboptimal growth conditions a complex response that leads to the acquisition of tolerance to different types of environmental stress. This response is characterised by enhanced expression of a number of genes which contain so-called stress-responsive elements (STREs) in their promoters. In addition, the cells accumulate under suboptimal conditions the putative stress protectant trehalose. In this work, we have examined the expression of four genes encoding subunits of the trehalose synthase complex, GGS1/TPS1, TPS2, TPS3 and TSL1. We show that expression of these genes is coregulated under stress conditions. Like for many other genes containing STREs, expression of the trehalose synthase genes is also induced by heat and osmotic stress and by nutrient starvation, and negatively regulated by the Ras-cAMP pathway. However, during fermentative growth only TSL1 shows an expression pattern like that of the STRE-controlled genes CTT1 and SSA3, while expression of the three other trehalose synthase genes is only transiently downregulated. This difference in expression might be related to the known requirement of trehalose biosynthesis for the control of yeast glycolysis and hence for fermentative growth. We conclude that the mere presence in the promoter of (an) active STRE(s) does not necessarily imply complete coregulation of expression. Additional mechanisms appear to fine tune the activity of STREs in order to adapt the expression of the downstream genes to specific requirements.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1617-4623
    Keywords: Trehalose synthase complex ; Stress-responsive element (STRE) ; Stress response ; Nutrients ; Ras-cAMP pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Saccharomyces cerevisiae cells show under suboptimal growth conditions a complex response that leads to the acquisition of tolerance to different types of environmental stress. This response is characterised by enhanced expression of a number of genes which contain so-called stress-responsive elements (STREs) in their promoters. In addition, the cells accumulate under suboptimal conditions the putative stress protectant trehalose. In this work, we have examined the expression of four genes encoding subunits of the trehalose synthase complex,GGS1/TPS1, TPS2, TPS3 andTSL1. We show that expression of these genes is coregulated under stress conditions. Like for many other genes containing STREs, expression of the trehalose synthase genes is also induced by heat and osmotic stress and by nutrient starvation, and negatively regulated by the Ras-cAMP pathway. However, during fermentative growth onlyTSL1 shows an expression pattern like that of the STRE-controlled genesCTT1 andSSA3, while expression of the three other trehalose synthase genes is only transiently down-regulated. This difference in expression might be related to the known requirement of trehalose biosynthesis for the control of yeast glycolysis and hence for fermentative growth. We conclude that the mere presence in the promoter of (an) active STRE(s) does not necessarily imply complete coregulation of expression. Additional mechanisms appear to fine tune the activity of STREs in order to adapt the expression of the downstream genes to specific requirements.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
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