The HXT2 gene of Saccharomyces cerevisiae is required for high-affinity glucose transport.

Kruckeberg, Arthur L.; Bisson, Linda F.

doi:10.1128/mcb.10.11.5903

Cited by 115 publications

(102 citation statements)

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“…Among 18 putative hexose transporter genes identified in S. cerevisiae, 7, HXT1 through HXT4, HXT6, HXT7, and GAL2, have thus far been shown to be capable of mediating glucose transport (33,36). The remaining HXT genes might encode hexose transporters that are not expressed under laboratory conditions, or they might encode transporters of other solutes.…”

Section: Discussionmentioning

confidence: 99%

Trinucleotide Insertions, Deletions, and Point Mutations in Glucose Transporters Confer K⁺Uptake inSaccharomyces cerevisiae

Liang

Herman

et al. 1998

Molecular and Cellular Biology

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Deletion of TRK1 and TRK2 abolishes high-affinity K ؉ uptake in Saccharomyces cerevisiae, resulting in the inability to grow on typical synthetic growth medium unless it is supplemented with very high concentrations of potassium. Selection for spontaneous suppressors that restored growth of trk1⌬ trk2⌬ cells on K ؉ -limiting medium led to the isolation of cells with unusual gain-of-function mutations in the glucose transporter genes HXT1 and HXT3 and the glucose/galactose transporter gene GAL2.86 Rb uptake assays demonstrated that the suppressor mutations conferred increased uptake of the ion. In addition to K ؉ , the mutant hexose transporters also conferred permeation of other cations, including Na ؉ . Because the selection strategy required such gain of function, mutations that disrupted transporter maturation or localization to the plasma membrane were avoided. Thus, the importance of specific sites in glucose transport could be independently assessed by testing for the ability of the mutant transporter to restore glucose-dependent growth to cells containing null alleles of all of the known functional glucose transporter genes. Twelve sites, most of which are conserved among eukaryotic hexose transporters, were revealed to be essential for glucose transport. Four of these have previously been shown to be essential for glucose transport by animal or plant transporters. Eight represented sites not previously known to be crucial for glucose uptake. Each suppressor mutant harbored a single mutation that altered an amino acid(s) within or immediately adjacent to a putative transmembrane domain of the transporter. Seven of 38 independent suppressor mutations consisted of in-frame insertions or deletions. The nature of the insertions and deletions revealed a striking DNA template dependency: each insertion generated a trinucleotide repeat, and each deletion involved the removal of a repeated nucleotide sequence.

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Section: Discussionmentioning

confidence: 99%

Trinucleotide Insertions, Deletions, and Point Mutations in Glucose Transporters Confer K⁺Uptake inSaccharomyces cerevisiae

Liang

Herman

et al. 1998

Molecular and Cellular Biology

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“…It is not established whether these regulatory functions of hexokinases are directly associated with the phosphorylating activity or another activity separate from phosphorylation. The study has been complicated by the multiplicity of hexose transport systems (8,24,27) and also by the fact that S. cerevisiae has three genes for glucose-phosphorylating enzymes (two for hexokinases and one for glucokinase) (17,28,30,31). Extensive analyses using combinations of mutations of individual kinase genes have clarified the roles of these enzymes (26,36,42).…”

Section: Discussionmentioning

confidence: 99%

The hexokinase gene is required for transcriptional regulation of the glucose transporter gene RAG1 in Kluyveromyces lactis.

Prior¹,

Mamessier²,

Fukuhara³

et al. 1993

Mol. Cell. Biol.

104

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The R4GI gene of Kluyveromyces lactis encodes a low-affinity glucose/fructose transporter. Its transcription is induced by glucose, fructose, and several other sugars. The RAG4, RAGS, and RAG8 genes are trans-acting genes controlling the expression of the RAG) gene. We report here the characterization of one of these genes, RAG5. The nucleotide sequence of the cloned RAGS gene indicated that it encodes a protein that is homologous to hexokinases of Saccharomyces cerevisiae. ragS mutants showed no detectable hexokinase or glucokinase activity, suggesting that the sugar kinase activity encoded by this gene is the only hexokinase in K. lactis. Both high-and low-affinity transport systems of glucose were affected in ragS mutants. The defect of the low-affinity component was found to be due to a block of transcription of the RAG) gene by the hexokinase mutation. In vivo complementation of the rag5 mutation by the K2 gene of S. cerevisiae and complementation of hxikl hxk2 mutations of S. cerevisiae by the RAGS gene showed that RAGS and HXK2 were equivalent for sugar-phosphorylating activity but that RA4GS could not restore glucose repression in the S. cerevisiae hexokinase mutants.

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“…The amino acid sequence of this clone exhibited 20 to 30% identity and 60 to 70% similarity to other members of this family, including the carriers transporting Ara , Gal (Szkutnicka et al, 1989;Kruckeberg and Bisson, 1990), Glc (Sauer and Tanner, 1989;Gould and Bell, 1990;Sauer et al, 1990), maltose (Cheng and Michels, 1989), and Xyl in both prokaryotes and eukaryotes. In addition to placing this clone in the MFS, sequence comparisons provided additional clues to the function of this transport system.…”

Section: Dlscusslonmentioning

confidence: 99%

Molecular Cloning, Immunochemical Localization to the Vacuole, and Expression in Transgenic Yeast and Tobacco of a Putative Sugar Transporter from Sugar Beet

Chiou

Bush

1996

Plant Physiol.

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, lllinois 61 801 Severa1 plant genes have been cloned that encode members of the sugar transporter subgroup of the major facilitator superfamily of transporters. Here we report the cloning, expression, and membrane localization of one of these porters found in sugar beet (Befa vulgaris L.). lhis clone, cDNA-1, codes for a protein with 490 amino acids and an estimated molecular m a s of 54 kD. l h e predicted membrane topology and sequence homology suggest that cDNA-1 is a member of the sugar transporter family. RNA gel blot analysis revealed that this putative sugar transporter is expressed in all vegetative tissues and expression increases with development in leaves. DNA gel blot analysis indicated that multiple gene copies exist for this putative sugar transporter in the sugar beet genome. Antibodies directed against small peptides representing the N-and C-terminal domains of the c D N A l protein identified a 40-kD polypeptide i n microsomes isolated from cDNA-1 -transformed yeast (Saccharomyces cerevisiae). Moreover, the same protein was identified in sugar beet and transgenic tobacco (Nicotiana tobacum L.) membrane fractions. Detailed analysis of the transporter's distribution across linear sucrose gradients and flotation centrifugations showed that it co-migrates with tonoplast membrane markers. We conclude that this carrier is located on the tonoplast membrane and that it may mediate sugar partitioning between the vacuole and cytoplasmic compartments.Although plants are photoautotrophic organisms, they are composed of many heterotrophic tissue systems, such as roots, flowers, seeds, and developing leaves, that must import organic nutrients to support growth and development. These nutrient-dependent cells are nonphotosynthetic and, therefore, must import previously assimilated carbon, usually as sugars, from photosynthetic tissues. This redistribution process between the photosynthetic (source) and heterotrophic (sink) tissues is known as assimilate partitioning, and it is a fundamental activity in plants as multicellular organisms. We are interested in plant sugar transporters because they are key players in this essential resource redistribution system.There are many sugar transporters in higher plants that mediate carbon distribution within cells and between organs. They are differentiated by physiological contributions, transport properties (substrate specificity, thermody-

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The HXT2 gene of Saccharomyces cerevisiae is required for high-affinity glucose transport.

Cited by 115 publications

References 58 publications

Trinucleotide Insertions, Deletions, and Point Mutations in Glucose Transporters Confer K⁺Uptake inSaccharomyces cerevisiae

Trinucleotide Insertions, Deletions, and Point Mutations in Glucose Transporters Confer K⁺Uptake inSaccharomyces cerevisiae

The hexokinase gene is required for transcriptional regulation of the glucose transporter gene RAG1 in Kluyveromyces lactis.

Molecular Cloning, Immunochemical Localization to the Vacuole, and Expression in Transgenic Yeast and Tobacco of a Putative Sugar Transporter from Sugar Beet

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The HXT2 gene of Saccharomyces cerevisiae is required for high-affinity glucose transport.

Cited by 115 publications

References 58 publications

Trinucleotide Insertions, Deletions, and Point Mutations in Glucose Transporters Confer K+Uptake inSaccharomyces cerevisiae

Trinucleotide Insertions, Deletions, and Point Mutations in Glucose Transporters Confer K+Uptake inSaccharomyces cerevisiae

The hexokinase gene is required for transcriptional regulation of the glucose transporter gene RAG1 in Kluyveromyces lactis.

Molecular Cloning, Immunochemical Localization to the Vacuole, and Expression in Transgenic Yeast and Tobacco of a Putative Sugar Transporter from Sugar Beet

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Trinucleotide Insertions, Deletions, and Point Mutations in Glucose Transporters Confer K⁺Uptake inSaccharomyces cerevisiae

Trinucleotide Insertions, Deletions, and Point Mutations in Glucose Transporters Confer K⁺Uptake inSaccharomyces cerevisiae