FIGURE 1.

Conserved serine S6 modulates calcineurin activity. The ability of Cnb1-S6A and Cnb1-S6D mutants to complement cnb1Δ yeast was assayed using calcineurin-dependent reporter gene assays and calcineurin-mediated ion-resistant growth assays. A, Cnb1Δ yeast harboring the CDRE-lacZ reporter gene were transformed with centromere-based plasmids expressing wild type Cnb1, Cnb1-S6A (S6A) or Cnb1-S6D (S6D). Yeast were subsequently grown in YPD (pH 5.5) in the presence or absence of added extracellular CaCl₂ (0, 10, 25, or 100 mm). Four hours after CaCl₂ stimulation, yeast were harvested for quantitative β-galactosidase assays. Data plotted are average of four independent yeast transformants ± S.D. B, Cnb1Δ yeast expressing the indicated CNB1 alleles were grown in YPD supplemented with increasing concentrations of LiCl (in mm) at 30 °C for 2 days. Growth was quantitated by measuring A₆₀₀. Yeast transformed with empty vector were included as a negative control. Data points are average of four independent yeast transformants assayed in parallel ± standard error.