Disordered clusters of Bak dimers rupture mitochondria during apoptosis.
During apoptosis, Bak and Bax undergo major conformational change and form symmetric dimers that coalesce to perforate the mitochondrial outer membrane via an unknown mechanism. We have employed cysteine labelling and linkage analysis to the full length of Bak in mitochondria. This comprehensive survey showed that in each Bak dimer the N-termini are fully solvent-exposed and mobile, the core is highly structured, and the C-termini are flexible but restrained by their contact with the membrane. Dimer-dimer interactions were more labile than the BH3:groove interaction within dimers, suggesting there is no extensive protein interface between dimers. In addition, linkage in the mobile Bak N-terminus (V61C) specifically quantified association between dimers, allowing mathematical simulations of dimer arrangement. Together, our data show that Bak dimers form disordered clusters to generate lipidic pores. These findings provide a molecular explanation for the observed structural heterogeneity of the apoptotic pore.
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia.
Rachel T
0000-0001-7456-478X
RT
Uren
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia.
Martin
0000-0002-0212-1207
M
O'Hely
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia.
Sweta
0000-0002-7787-5118
S
Iyer
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.
Ray
R
Bartolo
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia.
Melissa X
0000-0003-1454-9566
MX
Shi
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia.
Jason M
JM
Brouwer
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia.
Amber E
0000-0001-7894-7294
AE
Alsop
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia.
Grant
0000-0003-4251-8898
G
Dewson
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia.
Ruth M
0000-0002-7101-1925
RM
Kluck
D000818:Animals; D017209:Apoptosis; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000502:physiology*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D055503:Protein Multimerization; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000737:chemistry* / Q000378:metabolism*
C494772:BAK1 protein, human; D050998:bcl-2 Homologous Antagonist-Killer Protein
Bak; Bcl-2 proteins; apoptotic pore; biophysics; cell biology; cell death; disordered cluster; human; oligomer; structural biology