FIGURE 1.

Kch1 regulates HACS-dependent Ca²⁺ accumulation in response to tunicamycin. A and B, ⁴⁵Ca²⁺ uptake into cultures of S. cerevisiae strains that contain combinations of Kch1, Kch2, and Cch1 (strains K601, CS01, CS02, CS03, CS04) was measured after a 4-h incubation in SC-100 (10 mm KCl) medium in the presence or absence of 3 μg/ml tunicamycin plus 0.25 μg/ml FK506, as indicated. C, β-galactosidase activity of the above mentioned strains transformed with a CDRE-lacZ reporter gene (pAMS366) in SC medium in the presence of 2.5 μg/ml tunicamycin. Samples were collected at the indicated time points. D, wild type and kch1 mutants (K601 and CS02) were exposed to 2-fold dilutions of tunicamycin, incubated for 10 h, and stained with propidium iodide. Live and dead cells were counted by flow cytometry. In all panels, averages for three biological replicates (±S.D.) are shown, and significant differences between kch1 and KCH1 control cells are indicated (**; see “Experimental Procedures”).