A purified polypeptide for inhibiting binding of BCL-2 to IP3 receptors includes an amino acid sequence consisting of about 10 to 80 amino acids. The amino acid sequence has a sequence identity at least 90% homologous to a portion of SEQ ID NO:1. The polypeptide inhibits binding of Bcl-2 to IP3 receptors of cells that express IP3R and Bcl-2 and induces apoptosis in a cell.
