Dynamic reconfiguration of pro-apoptotic BAK on membranes.

The EMBO journal 2021 Oct 18

filter terms:

BAK and BAX, the effectors of intrinsic apoptosis, each undergo major reconfiguration to an activated conformer that self-associates to damage mitochondria and cause cell death. However, the dynamic structural mechanisms of this reconfiguration in the presence of a membrane have yet to be fully elucidated. To explore the metamorphosis of membrane-bound BAK, we employed hydrogen-deuterium exchange mass spectrometry (HDX-MS). The HDX-MS profile of BAK on liposomes comprising mitochondrial lipids was consistent with known solution structures of inactive BAK. Following activation, HDX-MS resolved major reconfigurations in BAK. Mutagenesis guided by our HDX-MS profiling revealed that the BCL-2 homology (BH) 4 domain maintains the inactive conformation of BAK, and disrupting this domain is sufficient for constitutive BAK activation. Moreover, the entire N-terminal region preceding the BAK oligomerisation domains became disordered post-activation and remained disordered in the activated oligomer. Removal of the disordered N-terminus did not impair, but rather slightly potentiated, BAK-mediated membrane permeabilisation of liposomes and mitochondria. Together, our HDX-MS analyses reveal new insights into the dynamic nature of BAK activation on a membrane, which may provide new opportunities for therapeutic targeting. © 2021 The Authors.

Citation

Jarrod J Sandow, Iris Kl Tan, Alan S Huang, Shashank Masaldan, Jonathan P Bernardini, Ahmad Z Wardak, Richard W Birkinshaw, Robert L Ninnis, Ziyan Liu, Destiny Dalseno, Daisy Lio, Giuseppi Infusini, Peter E Czabotar, Andrew I Webb, Grant Dewson. Dynamic reconfiguration of pro-apoptotic BAK on membranes. The EMBO journal. 2021 Oct 18;40(20):e107237