The X-ray structure of a BAK homodimer reveals an inhibitory zinc binding site.
BAK/BAX-mediated mitochondrial outer-membrane permeabilization (MOMP) drives cell death during development and tissue homeostasis from zebrafish to humans. In most cancers, this pathway is inhibited by BCL-2 family antiapoptotic members, which bind and block the action of proapoptotic BCL proteins. We report the 1.5 A crystal structure of calpain-proteolysed BAK, cBAK, to reveal a zinc binding site that regulates its activity via homodimerization. cBAK contains an occluded BH3 peptide binding pocket that binds a BID BH3 peptide only weakly . Nonetheless, cBAK requires activation by truncated BID to induce cytochrome c release in mitochondria isolated from bak/bax double-knockout mouse embryonic fibroblasts. The BAK-mediated MOMP is inhibited by low micromolar zinc levels. This inhibition is alleviated by mutation of the zinc-coordination site in BAK. Our results link directly the antiapoptotic effects of zinc to BAK.
Moldoveanu
Tudor
T
Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, QC, Canada H3G 1Y6. Electronic address: tudor.moldoveanu@stjude.org.
Liu
Qian
Q
Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, QC, Canada H3G 1Y6.
Tocilj
Ante
A
Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, QC, Canada H3G 1Y6.
Watson
Mark
M
GeminX Biotechnologies, Inc., Place du Parc, Montreal, QC, Canada H2X 4A5.
Shore
Gordon
G
Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, QC, Canada H3G 1Y6; GeminX Biotechnologies, Inc., Place du Parc, Montreal, QC, Canada H2X 4A5.
Gehring
Kalle
K
Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, QC, Canada H3G 1Y6. Electronic address: kalle.gehring@mcgill.ca.
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001665:Binding Sites; D002154:Calpain / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology*; D018360:Crystallography, X-Ray; D006801:Humans; D007624:KB Cells; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics; D012680:Sensitivity and Specificity; D017967:Zinc Compounds / Q000494:pharmacology*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics
C494772:BAK1 protein, human; C474007:Bax protein (53-86); D002712:Chlorides; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D017967:Zinc Compounds; D050998:bcl-2 Homologous Antagonist-Killer Protein; C016837:zinc chloride; D002154:Calpain