5wve
Apaf-1-Caspase-9 holoenzyme
Structural highlights
FunctionAPAF_HUMAN Oligomeric Apaf-1 mediates the cytochrome c-dependent autocatalytic activation of pro-caspase-9 (Apaf-3), leading to the activation of caspase-3 and apoptosis. This activation requires ATP. Isoform 6 is less effective in inducing apoptosis.[1] [2] Publication Abstract from PubMedMammalian intrinsic apoptosis requires activation of the initiator caspase-9, which then cleaves and activates the effector caspases to execute cell killing. The heptameric Apaf-1 apoptosome is indispensable for caspase-9 activation by together forming a holoenzyme. The molecular mechanism of caspase-9 activation remains largely enigmatic. Here, we report the cryoelectron microscopy (cryo-EM) structure of an apoptotic holoenzyme and structure-guided biochemical analyses. The caspase recruitment domains (CARDs) of Apaf-1 and caspase-9 assemble in two different ways: a 4:4 complex docks onto the central hub of the apoptosome, and a 2:1 complex binds the periphery of the central hub. The interface between the CARD complex and the central hub is required for caspase-9 activation within the holoenzyme. Unexpectedly, the CARD of free caspase-9 strongly inhibits its proteolytic activity. These structural and biochemical findings demonstrate that the apoptosome activates caspase-9 at least in part through sequestration of the inhibitory CARD domain. Mechanistic insights into caspase-9 activation by the structure of the apoptosome holoenzyme.,Li Y, Zhou M, Hu Q, Bai XC, Huang W, Scheres SH, Shi Y Proc Natl Acad Sci U S A. 2017 Feb 14;114(7):1542-1547. doi:, 10.1073/pnas.1620626114. Epub 2017 Jan 31. PMID:28143931[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also
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