The functional differences between pro-survival and pro-apoptotic B cell lymphoma 2 (Bcl-2) proteins depend on structural differences in their Bcl-2 homology 3 (BH3) domains

J Biol Chem. 2014 Dec 26;289(52):36001-17. doi: 10.1074/jbc.M114.610758. Epub 2014 Nov 3.


Bcl-2 homology 3 (BH3) domains are short sequence motifs that mediate nearly all protein-protein interactions between B cell lymphoma 2 (Bcl-2) family proteins in the intrinsic apoptotic cell death pathway. These sequences are found on both pro-survival and pro-apoptotic members, although their primary function is believed to be associated with induction of cell death. Here, we identify critical features of the BH3 domains of pro-survival proteins that distinguish them functionally from their pro-apoptotic counterparts. Biochemical and x-ray crystallographic studies demonstrate that these differences reduce the capacity of most pro-survival proteins to form high affinity "BH3-in-groove" complexes that are critical for cell death induction. Switching these residues for the corresponding residues in Bcl-2 homologous antagonist/killer (Bak) increases the binding affinity of isolated BH3 domains for pro-survival proteins; however, their exchange in the context of the parental protein causes rapid proteasomal degradation due to protein destabilization. This is supported by further x-ray crystallographic studies that capture elements of this destabilization in one pro-survival protein, Bcl-w. In pro-apoptotic Bak, we demonstrate that the corresponding distinguishing residues are important for its cell-killing capacity and antagonism by pro-survival proteins.

Keywords: Apoptosis; B cell Lymphoma 2 (Bcl-2) Family; Cell Death; Peptides; Protein Structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Apoptosis
  • Apoptosis Regulatory Proteins / chemistry*
  • Apoptosis Regulatory Proteins / physiology
  • Cell Survival
  • Cells, Cultured
  • Crystallography, X-Ray
  • Cytochromes c / metabolism
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Stability
  • bcl-X Protein / chemistry*
  • bcl-X Protein / physiology


  • Apoptosis Regulatory Proteins
  • BCL2L1 protein, human
  • BCL2L2 protein, human
  • bcl-X Protein
  • Cytochromes c

Associated data

  • PDB/4CIM
  • PDB/4CIN