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Functional characterization of the α‐glucoside transporter Sut1p from Schizosaccharomyces pombe , the first fungal homologue of plant sucrose transporters

2001; Wiley; Volume: 39; Issue: 2 Linguagem: Inglês

10.1046/j.1365-2958.2001.02237.x

1365-2958

Anke Reinders, John M. Ward,

Fungal and yeast genetics research

Disaccharide transporters have not previously been identified in Schizosaccharomyces pombe . This is in contrast to Saccharomyces cerevisiae in which several maltose permeases belonging to the sugar porter (SP) family have been characterized. Here we report that a novel S. pombe gene, sut1 + , encodes a proton‐coupled disaccharide uptake transporter in the glycoside–pentoside–hexuronide (GPH):cation symporter family. Previously, members of the GPH family were restricted to bacteria and plants. The closest homologues of sut1 + are the sucrose uptake transporters (SUTs) from higher plants that transport sucrose with a higher affinity than maltose. The transport function of Sut1p was analysed by expression in S. cerevisiae . Sut1p was found to transport maltose with a K m of 6.5 ± 0.4 mM and sucrose with a K m of 36.3 ± 9.7 mM. Therefore, the substrate specificity of Sut1p from S. pombe is different from that of its plant homologues. Glucose repression of sut1 + at the transcriptional level is also consistent with a physiological function for Sut1p in maltose uptake. These results indicate that, unlike S. cerevisiae , S. pombe utilizes maltose transporters derived from a common ancestor with the plant SUTs.