Figure 6. Bcl-2 inhibits Ca²⁺-ATPase activity of SERCA3b.

Ca²⁺-ATPase activity of SERCA3b was measured using microsomes isolated from HEK-293 cells transfected with a cDNA construct without the sequence for Bcl-2 (SE3/Vec) and microsomes isolated from HEK-293 cells transfected with a Bcl-2-encoding vector (SE3/Bcl-2). Ca²⁺-ATPase activities were normalized to the SERCA3b content in each sample and levels of SERCA3b and Bcl-2 were revealed by Western blotting with PL/IM430 and anti-Bcl-2 antibody, respectively. Data from an individual experiment are shown in (A). The values shown are the mean±S.E. for five sample replicates; the same trend was observed in eight different microsome isolations (Figure S2 in the Supplementary Information). Average Ca²⁺-ATPase activities of eight independent experiments are shown in (B). Ca²⁺-ATPase activities were normalized per 1 µg of microsomal proteins and then that value was divided by peak area of SERCA3b bands to determine the activity per unit SERCA3b.