Hxt13, Hxt15, Hxt16 and Hxt17 from Saccharomyces cerevisiae represent a novel type of polyol transporters

Sci Rep. 2016 Mar 21:6:23502. doi: 10.1038/srep23502.

Abstract

The genome of S. cerevisae encodes at least twenty hexose transporter-like proteins. Despite extensive research, the functions of Hxt8-Hxt17 have remained poorly defined. Here, we show that Hxt13, Hxt15, Hxt16 and Hxt17 transport two major hexitols in nature, mannitol and sorbitol, with moderate affinities, by a facilitative mechanism. Moreover, Hxt11 and Hxt15 are capable of transporting xylitol, a five-carbon polyol derived from xylose, the most abundant pentose in lignocellulosic biomass. Hxt11, Hxt13, Hxt15, Hxt16 and Hxt17 are phylogenetically and functionally distinct from known polyol transporters. Based on docking of polyols to homology models of transporters, we propose the architecture of their active site. In addition, we determined the kinetic parameters of mannitol and sorbitol dehydrogenases encoded in the yeast genome, showing that they discriminate between mannitol and sorbitol to a much higher degree than the transporters.

MeSH terms

  • L-Iditol 2-Dehydrogenase / metabolism*
  • Mannitol / metabolism*
  • Membrane Transport Proteins / chemistry
  • Membrane Transport Proteins / metabolism*
  • Molecular Docking Simulation
  • Monosaccharide Transport Proteins / chemistry
  • Monosaccharide Transport Proteins / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Sorbitol / metabolism*

Substances

  • HXT13 protein, S cerevisiae
  • HXT15 protein, S cerevisiae
  • Hxt16 protein, S cerevisiae
  • Hxt17 protein, S cerevisiae
  • Membrane Transport Proteins
  • Monosaccharide Transport Proteins
  • Saccharomyces cerevisiae Proteins
  • Mannitol
  • Sorbitol
  • L-Iditol 2-Dehydrogenase