Understanding CARD Tricks in Apoptosomes

While earlier studies of Apaf-1 holo-apoptosome architecture revealed the spectacular heptameric wheellike structure formed by Apaf-1, the central CARD disk responsible for caspase-9 recruitment remained incompletely resolved. In a recent issue of Structure, Su et al. (2017) describe a crystal structure of the complex between Apaf-1 CARD and caspase-9 CARD. Together with two recent cryo-EM structures, this work brings us closer to a full view of the holo-apoptosome.