Cytochrome c and dATP-mediated Oligomerization of Apaf-1 Is a Prerequisite for Procaspase-9 Activation
Year: 1999
Type: article
Abstract: To elucidate the mechanism of activation of procaspase-9 by Apaf-1, we produced recombinant full-length Apaf-1 and purified it to complete homogeneity. Here we show using gel filtration that full-length Apaf-1 exists as a monomer that can be transformed to an oligomeric complex made of at least eight subunits after binding to cytochrome c and dATP. Apaf-1 binds to cytochrome c in the absence of dATP but does not form the oligomeric complex. However, when dATP is added to the cytochrome c-bound Apaf-1 complex, complete oligomerization occurs, suggesting that oligomerization is driven by hydrolysis of dATP. This was supported by the observation that ATP, but not the nonhydrolyzable adenosine 5'-O-(thiotriphosphate), can induce oligomerization of the Apaf-1-cytochrome c complex. Like the spontaneously oligomerizing Apaf-530, which lacks its WD-40 domain, the oligomeric full-length Apaf-1-cytochrome c complex can bind and process procaspase-9 in the absence of additional dATP or cytochrome c. However, unlike the truncated Apaf-530 complex, the full-length Apaf-1 complex can release the mature caspase-9 after processing. Once released, mature caspase-9 can process procaspase-3, setting into motion the caspase cascade. These observations indicate that cytochrome c and dATP are required for oligomerization of Apaf-1 and suggest that the WD-40 domain plays an important role in oligomerization of full-length Apaf-1 and the release of mature caspase-9 from the Apaf-1 oligomeric complex.
Source: Journal of Biological Chemistry
Institutions: Thomas Jefferson University, Sidney Kimmel Cancer Center
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W2004877384