The osmotolerant fructophilic yeast Zygosaccharomyces rouxii employs two plasma-membrane fructose uptake systems belonging to a new family of yeast sugar transporters.
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&emsp14;mM and V(max)∼13&emsp14;mmol h(-1) g(-1)) and ZrFfz2 is a facilitator transporting glucose and fructose with similar capacity and affinity (K(m)∼200&emsp14;mM and V(max)∼4&emsp14;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.
Department of Membrane Transport, Institute of Physiology Academy of Sciences of the Czech Republic, v.v.i., Vídeňská 1083, Prague, 142 20, Czech Republic.|CBAA, Instituto Superior de Agromonia, TUL, 1349-017 Lisboa, Portugal.
Maria José
MJ
Leandro
Department of Membrane Transport, Institute of Physiology Academy of Sciences of the Czech Republic, v.v.i., Vídeňská 1083, Prague, 142 20, Czech Republic.
Hana
H
Sychrová
CBAA, Instituto Superior de Agromonia, TUL, 1349-017 Lisboa, Portugal.
Catarina
C
Prista
CBAA, Instituto Superior de Agromonia, TUL, 1349-017 Lisboa, Portugal.
Maria C
MC
Loureiro-Dias
D001692:Biological Transport; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000235:genetics; D005632:Fructose / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D020068:Zygosaccharomyces / Q000235:genetics* / Q000378:metabolism
D004271:DNA, Fungal; D005656:Fungal Proteins; D009004:Monosaccharide Transport Proteins; D005632:Fructose; D005947:Glucose