Figure 1. Alignment of BH3^Bak (human) with other BH3 only proteins Bim (Bcl2-interacting mediator of cell death), Puma (p53 upregulated modulator of apoptosis), Bax (Bcl-2-associated X protein) of human that are found to bind Bcl-xl in the available structure (PDB ID given in parentheses).