Structural, biochemical, and functional analyses of CED-9 recognition by the proapoptotic proteins EGL-1 and CED-4.
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.
Yan
Nieng
N
Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ 08544, USA.
Gu
Lichuan
L
Kokel
David
D
Chai
Jijie
J
Li
Wenyu
W
Han
Aidong
A
Chen
Lin
L
Xue
Ding
D
Shi
Yigong
Y
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004591:Electrophoresis, Polyacrylamide Gel; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D019076:Transgenes
D051017:Apoptosis Regulatory Proteins; D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins; C089224:Ced-4 protein, C elegans; C087233:Ced-9 protein, C elegans; C112486:EGL-1 protein, C elegans; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins