Figure 4.

Time course of the in vitro proteolysis of Cas by caspase-3. (A) In vitro–translated Cas was incubated with caspase-3 for the indicated times. Samples were subjected to SDS-PAGE, and Cas cleavage fragments were detected by autoradiography. Seven fragments with molecular masses of 74, 47, 46, 43, 35, 32, and 31 kDa were observed. (B) Cell lysates from control cells were used as a source of endogenous Cas and incubated with caspase-3 for the indicated times. Cas cleavage fragments with molecular masses of 74 and 31 kDa were detected on immunoblots probed with Cas mAb. Molecular mass standards are shown by the arrowheads on the left. Molecular masses of the cleavage products are shown by the arrows on the right.