scholarly journals Two glucose/xylose transporter genes from the yeast Candida intermedia: first molecular characterization of a yeast xylose–H+ symporter

2006 ◽  
Vol 395 (3) ◽  
pp. 543-549 ◽  
Author(s):  
Maria José Leandro ◽  
Paula Gonçalves ◽  
Isabel Spencer-Martins
Keyword(s):  
Sequence Data ◽  
High Capacity ◽  
Transport Systems ◽  
Partial Purification ◽  
Facilitated Diffusion ◽  
Xylose Transport ◽  
Candida Intermedia ◽  
Strain Isolation ◽  
Genes Encoding

Candida intermedia PYCC 4715 was previously shown to grow well on xylose and to transport this sugar by two different transport systems: high-capacity and low-affinity facilitated diffusion and a high-affinity xylose–proton symporter, both of which accept glucose as a substrate. Here we report the isolation of genes encoding both transporters, designated GXF1 (glucose/xylose facilitator 1) and GXS1 (glucose/xylose symporter 1) respectively. Although GXF1 was isolated by functional complementation of an HXT-null (where Hxt refers to hexose transporters) Saccharomyces cerevisiae strain, isolation of the GXS1 cDNA required partial purification and micro-sequencing of the transporter, identified by its relative abundance in cells grown on low xylose concentrations. Both genes were expressed in S. cerevisiae and the kinetic parameters of glucose and xylose transport were determined. Gxs1 is the first yeast xylose/glucose–H+ symporter to be characterized at the molecular level. Comparison of its amino acid sequence with available sequence data revealed the existence of a family of putative monosaccharide–H+ symporters encompassing proteins from several yeasts and filamentous fungi.

scholarly journals High capacity xylose transport in Candida intermedia PYCC 4715

2003 ◽  
Vol 3 (1) ◽  
pp. 45-52 ◽  
Author(s):  
Márk Gárdonyi ◽  
MÃ¥ns ÖSterberg ◽  
Carla Rodrigues ◽  
Isabel Spencer-Martins ◽  
Bärbel Hahn-Hägerdal
Keyword(s):  
High Capacity ◽  
Xylose Transport ◽  
Candida Intermedia

scholarly journals Transport and Utilization of Hexoses and Pentoses in the Halotolerant Yeast Debaryomyces hansenii

1999 ◽  
Vol 65 (8) ◽  
pp. 3594-3598 ◽  
Author(s):  
Alexandra Nobre ◽  
Cândida Lucas ◽  
Cecília Leão
Keyword(s):  
Growth Parameters ◽  
Carbon Sources ◽  
Debaryomyces Hansenii ◽  
Transport Systems ◽  
Facilitated Diffusion ◽  
Xylose Transport ◽  
Halotolerant Yeast ◽  
Consumption Rates ◽  
Biomass Yields ◽  
Proton Uptake

ABSTRACT Debaryomyces hansenii is a yeast species that is known for its halotolerance. This organism has seldom been mentioned as a pentose consumer. In the present work, a strain of this species was investigated with respect to the utilization of pentoses and hexoses in mixtures and as single carbon sources. Growth parameters were calculated for batch aerobic cultures containing pentoses, hexoses, and mixtures of both types of sugars. Growth on pentoses was slower than growth on hexoses, but the values obtained for biomass yields were very similar with the two types of sugars. Furthermore, when mixtures of two sugars were used, a preference for one carbon source did not inhibit consumption of the other. Glucose and xylose were transported by cells grown on glucose via a specific low-affinity facilitated diffusion system. Cells derepressed by growth on xylose had two distinct high-affinity transport systems for glucose and xylose. The sensitivity of labeled glucose and xylose transport to dissipation of the transmembrane proton gradient by the protonophore carbonyl cyanidem-chlorophenylhydrazone allowed us to consider these transport systems as proton symports, although the cells displayed sugar-associated proton uptake exclusively in the presence of NaCl or KCl. When the V max values of transport systems for glucose and xylose were compared with glucose- and xylose-specific consumption rates during growth on either sugar, it appeared that transport did not limit the growth rate.

Characterization of novel Na+-dependent nucleobase transport systems at the blood-testis barrier

2006 ◽  
Vol 290 (5) ◽  
pp. E968-E975 ◽  
Author(s):  
Ryo Kato ◽  
Tomoji Maeda ◽  
Toshihiro Akaike ◽  
Ikumi Tamai
Keyword(s):  
Sertoli Cells ◽  
Mammalian Cells ◽  
Transport Systems ◽  
Salvage Pathway ◽  
Nucleotide Biosynthesis ◽  
Equilibrative Nucleoside Transporters ◽  
Genes Encoding ◽  
Nucleobase Transport ◽  
Blood Testis Barrier

In the testis, nucleosides and nucleobases are important substrates of the salvage pathway for nucleotide biosynthesis, and one of the roles of Sertoli cells is to provide nutrients and metabolic precursors to spermatogenic cells located within the blood-testis barrier (BTB). We have already shown that concentrative and equilibrative nucleoside transporters are expressed and are functional in primary-cultured rat Sertoli cells as a BTB model, but little is known about nucleobase transport at the BTB or about the genes encoding specific nucleobase transporters in mammalian cells. In the present study, we examined the uptake of purine ([3H]guanine) and pyrimidine ([3H]uracil) nucleobases by primary-cultured rat Sertoli cells. The uptake of both nucleobases was time and concentration dependent. Kinetic analysis showed the involvement of three different transport systems in guanine uptake. In contrast, uracil uptake was mediated by a single Na+-dependent high-affinity transport system. Guanine uptake was inhibited by other purine nucleobases but not by pyrimidine nucleobases, whereas uracil uptake was inhibited only by pyrimidine nucleobases. In conclusion, it was suggested that there might be purine- or pyrimidine-selective nucleobase transporters in rat Sertoli cells.

The osmotolerant fructophilic yeast Zygosaccharomyces rouxii employs two plasma-membrane fructose uptake systems belonging to a new family of yeast sugar transporters

Microbiology ◽  
2011 ◽  
Vol 157 (2) ◽  
pp. 601-608 ◽  
Author(s):  
Maria José Leandro ◽  
Hana Sychrová ◽  
Catarina Prista ◽  
Maria C. Loureiro-Dias
Keyword(s):  
Plasma Membrane ◽  
Diffusion Mechanism ◽  
Sugar Transport ◽  
High Capacity ◽  
Transport Systems ◽  
Facilitated Diffusion ◽  
Sugar Transporters ◽  
Zygosaccharomyces Rouxii ◽  
New Family ◽  
Spoilage Yeasts

Owing to its high resistance to weak-acid preservatives and extreme osmotolerance, Zygosaccharomyces rouxii is one of the main spoilage yeasts of sweet foods and beverages. In contrast with Saccharomyces cerevisiae, Z. rouxii is a fructophilic yeast; it consumes fructose faster than glucose. So far, to our knowledge, no specific Z. rouxii proteins responsible for this fructophilic behaviour have been characterized. We have identified two genes encoding putative fructose transporters in the Z. rouxii CBS 732 genome. Heterologous expression of these two Z. rouxii ORFs in a S. cerevisiae strain lacking its own hexose transporters (hxt-null) and subsequent kinetic analysis of sugar transport showed that both proteins are functionally expressed at the plasma membrane: ZrFfz1 is a high-capacity fructose-specific facilitator (K m∼400 mM and V max∼13 mmol h−1 g−1) and ZrFfz2 is a facilitator transporting glucose and fructose with similar capacity and affinity (K m∼200 mM and V max∼4 mmol h−1 g−1). These two proteins together with the Zygosaccharomyces bailii Ffz1 fructose-specific transporter belong to a new family of sugar transport systems mediating the uptake of hexoses via the facilitated diffusion mechanism, and are more homologous to drug/H+ antiporters (regarding their primary protein structure) than to other yeast sugar transporters of the Sugar Porter family.

Approaches used to examine the mechanism and regulation of hexose transport in rat myoblasts

1986 ◽  
Vol 64 (11) ◽  
pp. 1081-1091 ◽  
Author(s):  
Tony D'Amore ◽  
Theodore C. Y. Lo
Keyword(s):  
Transport System ◽  
Transport Systems ◽  
Facilitated Diffusion ◽  
Hexose Transport ◽  
Plasma Membrane Vesicles ◽  
Diffusion Type ◽  
High Affinity ◽  
Isolation And Characterization ◽  
Transport Mutants

This review discusses some of the approaches and general criteria that we have used to examine the properties of the hexose transport system in undifferentiated L6 rat myoblasts. These approaches include studying the kinetics of hexose transport in whole cells and plasma membrane vesicles, the effects of various inhibitors on hexose transport, the isolation and characterization of hexose transport mutants, and the use of cytochalasin B (CB) to identify the transport component(s). Transport kinetics indicated that two transport systems are present in these cells. 2-Deoxy-D-glucose is transported primarily by the high affinity system, whereas 3-O-methyl-D-glucose is transported by the low affinity system. Furthermore, these two transport systems are inactivated to different extents by CB. CB has a higher binding affinity for the low affinity hexose transport system. The inhibitory effect of various hexose analogues also revealed the presence of two hexose transport systems. The effects of various ionophores and energy uncouplers on hexose transport suggest that the high affinity system is an active transport process, whereas the low affinity system is of the facilitated diffusion type. The high affinity system is also sensitive to sulfhydryl reagents, whereas the low affinity system is not. Further evidence for the presence of two transport systems comes from the characterization of hexose transport mutants. Two of the mutants isolated are shown to be defective in the high affinity transport system, but not in the low affinity transport system. These mutants are also defective in the CB low affinity binding site. Based on our results a tentative working model for hexose transport in L6 rat myoblasts is presented.

scholarly journals Genotypic and Phenotypic Variation in Pseudomonas aeruginosa Reveals Signatures of Secondary Infection and Mutator Activity in Certain Cystic Fibrosis Patients with Chronic Lung Infections

2011 ◽  
Vol 79 (12) ◽  
pp. 4802-4818 ◽  
Author(s):  
Ashley E. Warren ◽  
Carla M. Boulianne-Larsen ◽  
Christine B. Chandler ◽  
Kami Chiotti ◽  
Evgueny Kroll ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Virulence Factors ◽  
Dna Microarrays ◽  
Sequence Data ◽  
Secondary Infection ◽  
Multidrug Efflux ◽  
Content Type ◽  
Strain Isolation ◽  
Genes Encoding

ABSTRACTEvolutionary adaptation ofPseudomonas aeruginosato the cystic fibrosis lung is limited by genetic variation, which depends on rates of horizontal gene transfer and mutation supply. Because each may increase following secondary infection or mutator emergence, we sought to ascertain the incidence of secondary infection and genetic variability in populations containing or lacking mutators. Forty-nine strains collected over 3 years from 16 patients were phenotyped for antibiotic resistance and mutator status and were genotyped by repetitive-sequence PCR (rep-PCR), pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST). Though phenotypic and genetic polymorphisms were widespread and clustered more strongly within than between longitudinal series, their distribution revealed instances of secondary infection. Sequence data, however, indicated that interlineage recombination predated initial strain isolation. Mutator series were more likely to be multiply antibiotic resistant, but not necessarily more variable in their nucleotide sequences, than nonmutators. One mutator and one nonmutator series were sequenced at mismatch repair loci and analyzed for gene content using DNA microarrays. Both were wild type with respect tomutL, but mutators carried an 8-bpmutSdeletion causing a frameshift mutation. Both series lacked 126 genes encoding pilins, siderophores, and virulence factors whose inactivation has been linked to adaptation during chronic infection. Mutators exhibited loss of severalfold more genes having functions related to mobile elements, motility, and attachment. A 105-kb, 86-gene deletion was observed in one nonmutator that resulted in loss of virulence factors related to pyoverdine synthesis and elements of the multidrug efflux regulon. Diminished DNA repair activity may facilitate but not be absolutely required for rapid evolutionary change.

Isolation and characterization of the genes encoding antimicrobial neutrophil cationic peptides, defensins.

Ensho ◽  
1995 ◽  
Vol 15 (1) ◽  
pp. 33-41
Author(s):  
Isao Nagaoka ◽  
Noriko Ishihara ◽  
Akimasa Someya ◽  
Kazuhisa Iwabuchi ◽  
Shin Yomogida ◽  
...  
Keyword(s):  
Cationic Peptides ◽  
Isolation And Characterization ◽  
Genes Encoding
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