Figure 6.

Homo-oligomerization is required for the apoptotic activity of Bax. (A) The homo-oligomerization of Bax and its alanine-scanning mutants in DKO cells in the presence of tBid. The exact amino acid sequences of these mutations are illustrated in Supplementary Figure S5. DKO cells were transfected with the expression plasmids for the indicated alanine-scanning mutants in the presence of the tBid expression plasmid. Gel-filtration analysis was carried out as described in Figure 1. (B) The apoptotic activities of Bax and its alanine-scanning mutants in DKO cells in the presence of tBid. The apoptotic activities of these mutants were quantified as described in Figure 4 and Materials and Methods. (C) The homo-oligomerization of Bax and its alanine-scanning mutants in DKO cells in response to STS. DKO cells were transfected with the expression plasmids for the indicated G-Bax and its mutants. DMSO or STS (1 μM) was added to the cells 20 h after transfection. After 8 h, cells were harvested for gel-filtration analysis as described in Figure 1. (D) Apoptotic activities of Bax and alanine-scanning mutants in the DKO cells in response to STS. The apoptotic activities of these mutants were quantified as described in Figure 3 and Materials and Methods.