From Proteopediaproteopedia link
Bim BH3 peptide in complex with Bcl-xL
[B2CL1_HUMAN] Potent inhibitor of cell death. Inhibits activation of caspases (By similarity). Appears to regulate cell death by blocking the voltage-dependent anion channel (VDAC) by binding to it and preventing the release of the caspase activator, CYC1, from the mitochondrial membrane. Also acts as a regulator of G2 checkpoint and progression to cytokinesis during mitosis.  Isoform Bcl-X(S) promotes apoptosis.  [B2L11_HUMAN] Induces apoptosis and anoikis. Isoform BimL is more potent than isoform BimEL. Isoform Bim-alpha1, isoform Bim-alpha2 and isoform Bim-alpha3 induce apoptosis, although less potent than isoform BimEL, isoform BimL and isoform BimS. Isoform Bim-gamma induces apoptosis. Isoform Bim-alpha3 induces apoptosis possibly through a caspase-mediated pathway. Isoform BimAC and isoform BimABC lack the ability to induce apoptosis.     
Publication Abstract from PubMed
Get into the groove: The first high-resolution structure of a foldamer bound to a protein target is described (see picture; foldamer in sticks). The foldamer consists of alpha- and beta-amino acid residues and is bound to the anti-apoptotic protein Bcl-x(L). The overall binding mode and key interactions observed in the foldamer/Bcl-x(L) complex mimic those seen in complexes of Bcl-x(L) with natural alpha-peptide ligands. Additional contacts in the foldamer/Bcl-x(L) complex involving beta-amino acid residues appear to contribute to binding affinity.
High-Resolution Structural Characterization of a Helical alpha/beta-Peptide Foldamer Bound to the Anti-Apoptotic Protein Bcl-x(L).,Lee EF, Sadowsky JD, Smith BJ, Czabotar PE, Peterson-Kaufman KJ, Colman PM, Gellman SH, Fairlie WD Angew Chem Int Ed Engl. 2009 Feb 19;48(24):4318-4322. PMID:19229915
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.