Structural, biochemical, and functional analyses of CED-9 recognition by the proapoptotic proteins EGL-1 and CED-4

Mol Cell. 2004 Sep 24;15(6):999-1006. doi: 10.1016/j.molcel.2004.08.022.


Programmed cell death in Caenorhabditis elegans is initiated by the binding of EGL-1 to CED-9, which disrupts the CED-4/CED-9 complex and allows CED-4 to activate the cell-killing caspase CED-3. Here we demonstrate that the C-terminal half of EGL-1 is necessary and sufficient for binding to CED-9 and for killing cells. Structure of the EGL-1/CED-9 complex revealed that EGL-1 adopts an extended alpha-helical conformation and induces substantial structural rearrangements in CED-9 upon binding. EGL-1 interface mutants failed to bind to CED-9 or to release CED-4 from the CED-4/CED-9 complex, and were unable to induce cell death in vivo. A surface patch on CED-9, different from that required for binding to EGL-1, was identified to be responsible for binding to CED-4. These data suggest a working mechanism for the release of CED-4 from the CED-4/CED-9 complex upon EGL-1 binding and provide a mechanistic framework for understanding apoptosis activation in C. elegans.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Apoptosis Regulatory Proteins
  • Apoptosis*
  • Caenorhabditis elegans Proteins / chemistry*
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Calcium-Binding Proteins / metabolism*
  • Conserved Sequence
  • Crystallography, X-Ray
  • Electrophoresis, Polyacrylamide Gel
  • Hydrogen Bonding
  • Models, Molecular
  • Molecular Sequence Data
  • Mutation
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Proto-Oncogene Proteins / chemistry*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-bcl-2
  • Recombinant Fusion Proteins / metabolism
  • Repressor Proteins / chemistry
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Sequence Homology, Amino Acid
  • Transgenes


  • Apoptosis Regulatory Proteins
  • Caenorhabditis elegans Proteins
  • Calcium-Binding Proteins
  • Ced-4 protein, C elegans
  • Ced-9 protein, C elegans
  • EGL-1 protein, C elegans
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • Recombinant Fusion Proteins
  • Repressor Proteins

Associated data

  • PDB/1TY4