Abstract
Apoptotic protease activating factor-1 (Apaf-1) has been identified as a proximal activator of caspase-9 in cell death pathways that trigger mitochondrial damage and cytochrome c release. The mechanism of Apaf-1 action is unclear but has been proposed to involve the clustering of caspase-9 molecules, thereby facilitating autoprocessing of adjacent zymogens. Here we show that Apaf-1 can dimerize via the CED-4 homologous and linker domains of the molecule providing a means by which Apaf-1 can promote the clustering of caspase-9 and facilitate its activation. Apaf-1 dimerization was repressed by the C-terminal half of the molecule, which contains multiple WD-40 repeats, but this repression was overcome in the presence of cytochrome c and dATP. Removal of the WD-40 repeat region resulted in a constitutively active Apaf-1 that exhibited greater cytotoxicity in transient transfection assays when compared with full-length Apaf-1. These data suggest a mechanism for Apaf-1 function and reveal an important regulatory role for the WD-40 repeat region.
Original language | English |
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Pages (from-to) | 20855-60 |
Number of pages | 6 |
Journal | Journal of Biological Chemistry |
Volume | 274 |
Issue number | 30 |
Publication status | Published - 23 Jul 1999 |
Keywords
- Apoptosis
- Apoptotic Protease-Activating Factor 1
- Binding Sites
- Caspase 9
- Caspases
- Cell Line
- Dimerization
- Enzyme Activation
- Humans
- Proteins
- Repetitive Sequences, Nucleic Acid
- Saccharomyces cerevisiae