Fig. 4.
Bcl-xL antagonizes Bax D68R in yeast but binds only weakly to a Bax D68R BH3 peptide. (A) Bcl-xL counters growth suppression of yeast by Bax D68R. Yeast cotransformed with constructs encoding the indicated prosurvival proteins and Bax or Bax D68R (all full length), each under the control of an inducible (GAL) promoter were spotted onto repressing glucose (OFF) or inducing galactose (ON) plates as 5-fold serial dilutions. Images are representative of 2 independent experiments. (B) Relative affinity (IC50 in μM) of the C-terminally truncated prosurvival proteins (see Materials and Methods) for WT or D68R Bax BH3 peptides (34-mers), determined by solution competition assays. Data shown represent means ± 1 SD of 2 independent experiments. *Data from experiments using human Bcl-xL Δ45–84 ΔC24; comparable results were obtained with mouse Bcl-xL ΔC24.