Expression and activity assays of Gtr1 wild-type (WT), cysteine-less (Cys-less), Arg37Cys and Val67Cys proteins. (A) Western blot analysis using anti-His antibody. (B) GTP hydrolytic activity of WT (·) Cys-less (❑), Arg37Cys (▴) and Val67Cys (Δ) shown as the amount of GDP produced as a function of time. (C) GTPase activity of Gtr1 mutants at 60 min of incubation relative to that for the WT protein. 100 % is equivalent to 1.76 nmol GDP mg-1 protein. The presented data are means ± SD (n = 2-3 independent experiments). *, Significantly different from WT (Student’s t-test P < 0.05).