Journal article
Apoptotic pore formation is associated with in-plane insertion of Bak or Bax central helices into the mitochondrial outer membrane
D Westphal, G Dewson, M Menard, P Frederick, S Iyer, R Bartolo, L Gibson, PE Czabotar, BJ Smith, JM Adams, RM Kluck
Proceedings of the National Academy of Sciences of the United States of America | Published : 2014
Abstract
The pivotal step on the mitochondrial pathway to apoptosis is permeabilization of the mitochondrial outer membrane (MOM) by oligomers of the B-cell lymphoma-2 (Bcl-2) family members Bak or Bax. However, how they disrupt MOM integrity is unknown. A longstanding model is that activated Bak and Bax insert two α-helices, α5 and α6, as a hairpin across the MOM, but recent insights on the oligomer structures question this model. We have clarified how these helices contribute to MOM perforation by determining that, in the oligomers, Bak α5 (like Bax α5) remains part of the protein core and that a membrane-impermeable cysteine reagent can label cysteines placed at many positions in a5 and a6 of both..
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Funding Acknowledgements
We thank T. Kratina for technical support; N. Church, J.-G. Zhang, R. Uren, C. Hockings, and M. Ritchie for advice on isoelectric focusing and statistics; P. Colman for comments on the manuscript; and T. Kitamura for the pMX-IG vector. This work was supported in part by a Deutsche Forschungsgemeinschaft postdoctoral fellowship (to D.W.), the National Health and Medical Research Council (575559 and 1016701), the Australian Research Council (FT100100754 and FT100100791), the Leukemia and Lymphoma Society, the Victorian State Government Operational Infrastructure Support, and the Australian Government National Health and Medical Research Council Independent Research Institute Infrastructure Support Scheme.