Identifying the trigger of c-IAPs: structural and functional characterization of CARD-mediated modulation of ubiquitin ligase activity.

In this issue of Molecular Cell, Lopez et al. (2011) examine the caspase-recruitment domain (CARD) of c-IAP1 to reveal an intriguing mechanism in which conformational changes of the CARD determine c-IAP1's ubiquitin ligase activity, with implications for regulation of cell proliferation and survival by the IAPs.