ジャーナル: Science / 年: 2023 タイトル: Structural basis for SMAC-mediated antagonism of caspase inhibition by the giant ubiquitin ligase BIRC6. 著者: Larissa Dietz / Cara J Ellison / Carlos Riechmann / C Keith Cassidy / F Daniel Felfoldi / Adán Pinto-Fernández / Benedikt M Kessler / Paul R Elliott / 要旨: Certain inhibitor of apoptosis (IAP) family members are sentinel proteins that prevent untimely cell death by inhibiting caspases. Antagonists, including second mitochondria-derived activator of ...Certain inhibitor of apoptosis (IAP) family members are sentinel proteins that prevent untimely cell death by inhibiting caspases. Antagonists, including second mitochondria-derived activator of caspases (SMAC), regulate IAPs and drive cell death. Baculoviral IAP repeat-containing protein 6 (BIRC6), a giant IAP with dual E2 and E3 ubiquitin ligase activity, regulates programmed cell death through unknown mechanisms. We show that BIRC6 directly restricts executioner caspase-3 and -7 and ubiquitinates caspase-3, -7, and -9, working exclusively with noncanonical E1, UBA6. Notably, we show that SMAC suppresses both mechanisms. Cryo-electron microscopy structures of BIRC6 alone and in complex with SMAC reveal that BIRC6 is an antiparallel dimer juxtaposing the substrate-binding module against the catalytic domain. Furthermore, we discover that SMAC multisite binding to BIRC6 results in a subnanomolar affinity interaction, enabling SMAC to competitively displace caspases, thus antagonizing BIRC6 anticaspase function.
DiabloIAP-bindingmitochondrialprotein / Diablo homolog / mitochondrial / Direct IAP-binding protein with low pI / Second mitochondria- ...Diablo homolog / mitochondrial / Direct IAP-binding protein with low pI / Second mitochondria-derived activator of caspase / Smac