(a) Growth assay of YSL2-1 cells expressing GeSUTs. Yeast cells
expressing GeSUTs, an empty vector, and the AtSUC2 were
seriously diluted and cultured on solid media (pH 5 or 7) supplemented
with maltose or sucrose, respectively. Images were taken
after incubation at 30 °C for 4-6 days. (b) Time-dependent uptake
activity of YSL2-1 to sucrose. Yeast cells in (a) were incubated with 1
mM sucrose containing 1.5 μCi [14C]sucrose and then cells were
harvested at indicated time point for radioactivity measurement.
Significant differences from cells expressing the empty vector were
determined. (c) Kinetic of GeSUT4 transport. Transformed cells
were incubated in media containing indicated concentrations of sucrose
with same molar ratio of [14C]sucrose. After 10 mins, cells were
harvested and analyzed for radioactivity. (d) Substrate specificity ofGeSUT4 transport activity. Transformed cells were
incubated for 10 mins with the control solution with or without 10 times
concentrated sugars (Suc, sucrose; Glc, glucose; Gal, galactose; Fru,
fructose; Man, mannose; Mal, maltose). Relative uptake rate was
calculated compared to cells incubated with the control solution. The
background uptake of non-transformed cells (empty) was also shown.
Significant differences from cells incubated in the control solution
were determined. (e) Effect of pH and protonophore on GeSUT4
uptake activity. Yeast cells expressing an empty vector, AtSUC2
or GeSUT4 were analyzed. Significant differences from results
measured under the pH 5 condition were determined. Results are mean ± SE
(n=3 in b, c, e or 5 in d).