Figure 1. Carboxyl-terminally tagged MCA1 and MCA2 retained their activities.

(A) Ca²⁺ accumulation in yeast mid1 mutant cells carrying various plasmids. Cells were grown to the exponential phase in SD.Ca100 medium and incubated for an additional 2 h at 30°C with 185 kBq/ml of ⁴⁵CaCl₂ (1.81 kBq/nmol). The radioactivity that accumulated in these cells was measured as described in the Materials and Methods. The mean for at least three independent experiments (± SD) is shown for each yeast strain. The plasmids carried by the mid1 mutant are as follows: YEpT-MCA1-6H (for MCA1-6H), YEpT-MCA2-6H (MCA2-6H), and YEpTDHXho (control). *, p<0.001 versus control. (B) Ca²⁺ accumulation in insect Sf9 cells expressing MCA1-6H or MCA2-6H. Cells were infected with a recombinant baculovirus carrying MCA1-6H or MCA2-6H cDNA at a MOI of 1.0 and incubated for 2 days at 25°C. Infected cells were harvested, washed, and resuspended in uptake solution as described in the Materials and Methods. The suspension was incubated for 30 min with 11.1 kBq/ml of ⁴⁵CaCl₂ (0.444 kBq/nmol). The radioactivity that accumulated in the cells was measured as described above. The mean for three independent experiments (± SD) is shown for Sf9 cells expressing MCA1-6H, MCA2-6H, or β-glucuronidase (control). **, p<0.05 versus control.