Kinetic characterization of individual hexose transporters of Saccharomyces cerevisiae and their relation to the triggering mechanisms of glucose repression
| Autor: | Eckhard Boles, Michael Ciriacy, Elke Reifenberger |
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| Rok vydání: | 1997 |
| Předmět: |
Snf3
Glycoside Hydrolases Monosaccharide Transport Proteins Transcription Genetic Glucose uptake Saccharomyces cerevisiae Biochemistry Fungal Proteins chemistry.chemical_compound Galactokinase Gene Expression Regulation Fungal Monosaccharide Hexose Hexose transport chemistry.chemical_classification biology beta-Fructofuranosidase Glucose transporter alpha-Glucosidases Maltose biology.organism_classification Kinetics Glucose chemistry Enzyme Induction Signal Transduction |
| Zdroj: | European journal of biochemistry. 245(2) |
| ISSN: | 0014-2956 |
| Popis: | In Saccharomyces cerevisiae, there are a large number of genes (HXT1-HXT17/SNF3/RGT2) encoding putative hexose transporters which, together with a galactose permease gene (GAL2), belong to a superfamily of monosaccharide facilitator genes. We have performed a systematic analysis of the HXT1-7 and GAL2 genes and their function in hexose transport. Glucose uptake was below the detection level in the hxt1-7 null strain growing on maltose. Determination of the kinetic parameters of individual hexose transporter-related proteins (Hxtp) expressed in the hxt null background revealed Hxt1p and Hxt3p as low-affinity transporters (Km(glucose) = 50-100 mM), Hxt2p and Hxt4p as moderately low in affinity (Km(glucose) about 10 mM), and Hxt6p, Hxt7p as well as Gal2p as high-affinity transporters (Km(glucosse) = 1-2 mM). However, Hxt2p kinetics in cells grown on low glucose concentrations showed a high-affinity (Km = 1.5 mM) and a low-affinity component (Km = 60 mM). Furthermore, we investigated the involvement of glucose transport in glucose signalling. Glucose repression of MAL2, SUC2 and GAL1 was not dependent on a specific transporter but, instead, the strength of the repression signal was dependent on the level of expression, the properties of the individual transporters and the kind of sugar transported. The strength of the glucose repression signal correlated with the glucose consumption rates in the different strains, indicating that glucose transport limits the provision of a triggering signal rather then being directly involved in the triggering mechanism. |
| Databáze: | OpenAIRE |
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