title: Dissociation of Bak α1 helix from the core and latch domains is required for apoptosis.
abstract: During apoptosis, Bak permeabilizes mitochondria after undergoing major conformational changes, including poorly defined N-terminal changes. Here, we characterize those changes using 11 antibodies that were epitope mapped using peptide arrays and mutagenesis. After Bak activation by Bid, epitopes throughout the α1 helix are exposed indicating complete dissociation of α1 from α2 in the core and from α6-α8 in the latch. Moreover, disulfide tethering of α1 to α2 or α6 blocks cytochrome c release, suggesting that α1 dissociation is required for further conformational changes during apoptosis. Assaying epitope exposure when α1 is tethered shows that Bid triggers α2 movement, followed by α1 dissociation. However, α2 reaches its final position only after α1 dissociates from the latch. Thus, α1 dissociation is a key step in unfolding Bak into three major components, the N terminus, the core (α2-α5) and the latch (α6-α8).
authors.affiliation: 1] The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia [2] Department of Medical Biology, University of Melbourne, Parkville, Victoria 3052, Australia.
authors.forename: Amber E
authors.identifier: 0000000178947294
authors.initials: AE
authors.lastname: Alsop
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia.
authors.forename: Stephanie C
authors.initials: SC
authors.lastname: Fennell
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia.
authors.forename: Ray C
authors.initials: RC
authors.lastname: Bartolo
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia.
authors.forename: Iris K L
authors.initials: IK
authors.lastname: Tan
authors.affiliation: 1] The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia [2] Department of Medical Biology, University of Melbourne, Parkville, Victoria 3052, Australia.
authors.forename: Grant
authors.initials: G
authors.lastname: Dewson
authors.affiliation: 1] The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia [2] Department of Medical Biology, University of Melbourne, Parkville, Victoria 3052, Australia.
authors.forename: Ruth M
authors.identifier: 0000000271011925
authors.initials: RM
authors.lastname: Kluck
mesh_terms: D000818:Animals; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D002460:Cell Line; D002461:Cell Line, Transformed; D018604:Epitope Mapping; D006801:Humans; D051379:Mice; D016297:Mutagenesis, Site-Directed; D040081:Protein Array Analysis; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism*
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D050998:bcl-2 Homologous Antagonist-Killer Protein