BAX Activation: Mutations Near Its Proposed Non-canonical BH3 Binding Site Reveal Allosteric Changes Controlling Mitochondrial Association
Michael A Dengler, Adeline Y Robin, Leonie Gibson, Mark X Li, Jarrod J Sandow, Sweta Iyer, Andrew Webb, Dana Westphal, Grant Dewson, Jerry M Adams
CELL REPORTS | CELL PRESS | Published : 2019
To elicit apoptosis, BAX metamorphoses from an inert cytosolic monomer into homo-oligomers that permeabilize the mitochondrial outer membrane (MOM). A long-standing puzzle is that BH3 domains apparently activate BAX by not only its canonical groove but also a proposed site involving helices α1 and α6. Our mutagenesis studies reveal that late steps like oligomerization require activation through the groove but probably not earlier steps like MOM association. Conversely, α1 or α6 obstruction and alanine mutagenesis scanning implicate these helices early in BAX activation. The α1 and α6 mutations lowered BH3 binding, altered the BAX conformation, and reduced its MOM translocation and integratio..View full abstract
Awarded by National Health and Medical Research Council, Australia
Awarded by SCOR grant from the Leukemia and Lymphoma Society, United States
Awarded by Australian Government Independent Research Institute Infrastructure Support Scheme
The authors thank Peter Colman, Peter Czabotar, and Ruth Kluck for advice and insights on BAX rearrangements, and Colin Hockings for recombinant BID proteins. This work was supported by program grant 1016701 (to J.M.A) and project grant 1078924 (to G.D.) from the National Health and Medical Research Council, Australia, and SCOR grant 7001-13 from the Leukemia and Lymphoma Society, United States (to J.M.A), as well as operational infrastructure grants through the Australian Government Independent Research Institute Infrastructure Support Scheme (9000220) and the Victorian State Government Operational Infrastructure Support Program. Crystallization experiments were performed at the CSIRO C3 Crystallisation Centre and diffraction data were collected at the Australian Synchrotron.