Mapping of gene controlling thiamine transport inSaccharomyces cerevisiae

Yeast cells take up thiamin from the extracellular environment by an active transport system with a pH optimum of 4.5 and a K m value of 0.18 M, and thiamin in the cells is concentrated ϳ10,000-fold over extracellular levels (1). The thiamin transport system is more specific for the chemical structure of the pyrimidine moiety than the thiazole moiety of thiamin (2). Saccharomyces cerevisiae also secretes a thiamin-repressible acid phosphatase encoded by PHO3 gene (3, 4) in a periplasmic space. Since yeast cells cannot take up thiamin phosphate esters, the PHO3 protein with a high affinity for thiamin phosphate esters appears to hydrolyze them before the uptake (5, 6), and then thiamin is converted to thiamin pyrophosphate (TPP) 1 by thiamin pyrophosphokinase (EC 2.7.6.2) encoded by the THI80 gene (7). TPP is an important cofactor in the energy metabolism (8) and is a negative effector of the regulation mechanism of thiamin metabolism in yeast cells (9).We report here the isolation and characterization of S. cerevisiae THI10 gene and provide evidence that the THI10 gene encodes for a thiamin transport carrier protein. The predicted THI10 protein is highly hydrophobic and shows significant sequence similarities to yeast uracil and allantoin transport proteins. The thiamin transport activity and the thiamin binding activity in the yeast plasma membrane fraction in thi10 null strain cells were restored when the THI10 open reading frame (ORF) was expressed by yeast GAL1 promoter. The regulation of the THI10 gene expression was also investigated.

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Mapping of gene controlling thiamine transport inSaccharomyces cerevisiae

Cited by 3 publications

References 12 publications

Thiamin metabolism and thiamin diphosphate-dependent enzymes in the yeast Saccharomyces cerevisiae: genetic regulation

Thiamin metabolism and thiamin diphosphate-dependent enzymes in the yeast Saccharomyces cerevisiae: genetic regulation

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Isolation and Characterization of a Thiamin Transport Gene,THI10, from Saccharomyces cerevisiae

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