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Structural model of active Bax at the membrane
#MMPMID25458844
Bleicken S
; Jeschke G
; Stegmueller C
; Salvador-Gallego R
; García-Sáez AJ
; Bordignon E
Mol Cell
2014[Nov]; 56
(4
): 496-505
PMID25458844
show ga
Bax plays a central role in the mitochondrial pathway of apoptosis. Upon
activation, cytosolic Bax monomers oligomerize on the surface of mitochondria and
change conformation concertedly to punch holes into the outer membrane. The
subsequent release of cytochrome c initiates cell death. However, the structure
of membrane-inserted Bax and its mechanism of action remain largely unknown.
Here, we propose a 3D model of active Bax at the membrane based on double
electron-electron resonance (DEER) spectroscopy in liposomes and isolated
mitochondria. We show that active Bax is organized at the membrane as assemblies
of dimers. In addition to a stable dimerization domain, each monomer contains a
more flexible piercing domain involved in interdimer interactions and pore
formation. The most important structural change during Bax activation is the
opening of the hairpin formed by helices 5 and 6, which adopts a clamp-like
conformation central to the mechanism of mitochondrial permeabilization.