RESUMEN
The yeast Snf3 protein has been described to function as a sensor for low concentrations of extracellular glucose. We have found that Snf3 is able to transduce a signal in the complete absence of extracellular glucose. High basal activity of the HXT7 promoter during growth on ethanol required Snf3 as well as other components of the signalling pathway activated by Snf3. Moreover, the C-terminal domain of Snf3 was sufficient to complement the role of Snf3 in this regulation. As the C-terminal tail of Snf3 interacted with other components at the plasma membrane independent of the carbon source, our data suggest that Snf3 is involved in signalling complexes which can be activated by other signals than extracellular glucose.
Asunto(s)
Glucosa/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas de Transporte de Monosacáridos/metabolismo , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/metabolismo , Transducción de Señal , Secuencia de Bases , Transporte Biológico , Cartilla de ADN , Transcripción GenéticaRESUMEN
The hexose transporter family of Saccharomyces cerevisiae comprises 18 proteins (Hxt1-17, Gal2). Here, we demonstrate that all these proteins, except Hxt12, and additionally three members of the maltose transporter family (Agt1, Ydl247, Yjr160) are able to transport hexoses. In a yeast strain deleted for HXT1-17, GAL2, AGT1, YDL247w and YJR160c, glucose consumption and transport activity were completely abolished. However, as additional deletion of the glucose sensor gene SNF3 partially restored growth on hexoses, our data indicate the existence of even more proteins able to transport hexoses in yeast.
Asunto(s)
Eliminación de Gen , Hexosas/metabolismo , Proteínas de Transporte de Monosacáridos/genética , Saccharomyces cerevisiae/metabolismo , Secuencia de Bases , Clonación Molecular , Cartilla de ADN , Proteínas de Transporte de Monosacáridos/metabolismo , Saccharomyces cerevisiae/genéticaRESUMEN
Saccharomyces cerevisiae HTR1 mutants are severely impaired in the uptake of glucose. We have cloned dominant HTR1 mutant alleles and show that they encode mutant forms of the Mth1 protein. Mth1 is shown to be involved in carbon source-dependent regulation of its own, invertase and hexose transporter gene expression. The mutant forms block the transduction of the Snf3- and Rgt2-mediated glucose signals upstream of the Rgt1 transcriptional regulator.
Asunto(s)
Proteínas de Ciclo Celular , Proteínas Fúngicas/genética , Glucosa/fisiología , Proteínas de la Membrana/fisiología , Proteínas de Transporte de Monosacáridos/fisiología , Proteínas Represoras , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Transducción de Señal/genética , Proteínas Adaptadoras Transductoras de Señales , Alelos , Clonación Molecular , Regulación Fúngica de la Expresión Génica , Glicósido Hidrolasas/metabolismo , Proteínas de Transporte de Monosacáridos/genética , Mutación , Proteínas de Unión al ARN , Saccharomyces cerevisiae/fisiología , beta-FructofuranosidasaRESUMEN
The trehalose content in Saccharomyces cerevisiae can be significantly manipulated by including trehalose at an appropriate level in the growth medium. Its uptake is largely dependent on the expression of AGT1, which encodes an alpha-glucoside transporter. The trehalose found in a tps1 mutant of trehalose synthase may therefore largely reflect its uptake from the enriched medium that was employed.