Identification of an activation site in Bak and mitochondrial Bax triggered by antibodies Academic Article uri icon


  • During apoptosis, Bak and Bax are activated by BH3-only proteins binding to the α2-α5 hydrophobic groove; Bax is also activated via a rear pocket. Here we report that antibodies can directly activate Bak and mitochondrial Bax by binding to the α1-α2 loop. A monoclonal antibody (clone 7D10) binds close to α1 in non-activated Bak to induce conformational change, oligomerization, and cytochrome c release. Anti-FLAG antibodies also activate Bak containing a FLAG epitope close to α1. An antibody (clone 3C10) to the Bax α1-α2 loop activates mitochondrial Bax, but blocks translocation of cytosolic Bax. Tethers within Bak show that 7D10 binding directly extricates α1; a structural model of the 7D10 Fab bound to Bak reveals the formation of a cavity under α1. Our identification of the α1-α2 loop as an activation site in Bak paves the way to develop intrabodies or small molecules that directly and selectively regulate these proteins.


  • Iyer, S
  • Anwari, K
  • Alsop, AE
  • Yuen, WS
  • Huang, DCS
  • Carroll, J
  • Smith, NA
  • Smith, BJ
  • Dewson, G
  • Kluck, RM

publication date

  • 2016

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