TY - JOUR
T1 - BH3-in-groove dimerization initiates and helix 9 dimerization expands Bax pore assembly in membranes
AU - Zhang, Zhi
AU - Subramaniam, Sabareesh
AU - Kale, Justin
AU - Liao, Chenyi
AU - Huang, Bo
AU - Brahmbhatt, Hetal
AU - Condon, Samson G.F.
AU - Lapolla, Suzanne M.
AU - Hays, Franklin A.
AU - Ding, Jingzhen
AU - He, Feng
AU - Zhang, Xuejun C.
AU - Li, Jianing
AU - Senes, Alessandro
AU - Andrews, David W.
AU - Lin, Jialing
N1 - Funding Information:
We thank Kathy Kyler for editing the paper. This work was supported by NIH grant R01GM062964 and OCAST grant HR10-121 to J. Lin, NIH grant R01GM099752 and NSF grant CHE-1415910 to AS, NIH grant P20GM104934 and P20GM103639 to FAH, NLM grant 5T15LM007359 to SGFC, and CIHR grant FRN12517 to DWA and Brian Leber. Computer resources for MD simulations were provided by Vermont Advanced Computing Core (VACC) and the Extreme Science and Engineering Discovery Environment (XSEDE) supported by National Science Foundation grant number ACI-1053575.
Publisher Copyright:
© 2015 The Authors.
PY - 2016/1/1
Y1 - 2016/1/1
N2 - Pro-apoptotic Bax induces mitochondrial outer membrane permeabilization (MOMP) by forming oligomers through a largely undefined process. Using site-specific disulfide crosslinking, compartment-specific chemical labeling, and mutational analysis, we found that activated integral membrane Bax proteins form a BH3-in-groove dimer interface on the MOM surface similar to that observed in crystals. However, after the α5 helix was released into the MOM, the remaining interface with α2, α3, and α4 helices was rearranged. Another dimer interface was formed inside the MOM by two intersected or parallel α9 helices. Combinations of these interfaces generated oligomers in the MOM. Oligomerization was initiated by BH3-in-groove dimerization, without which neither the other dimerizations nor MOMP occurred. In contrast, α9 dimerization occurred downstream and was required for release of large but not small proteins from mitochondria. Moreover, the release of large proteins was facilitated by α9 insertion into the MOM and localization to the pore rim. Therefore, the BH3-in-groove dimerization on the MOM nucleates the assembly of an oligomeric Bax pore that is enlarged by α9 dimerization at the rim. Synopsis Apoptotic Bax oligomers permeabilize the mitochondrial outer membrane. Structural analyses and modeling of Bax interactions at mitochondria show that BH3-in-groove dimerization on membranes initiates the pore assembly, which is followed by helix 9 dimerization-mediated expansion. Bax protein oligomerization initiates with helices α2-α5 forming a BH3-in-groove dimer interface on the membrane surface. The BH3-in-groove dimer interface is rearranged after α5 insertion into the membrane. α9 helices from neighboring Bax molecules form another dimer interface inside the membrane linking the BH3-in-groove dimers to higher order oligomers. α9 insertion and dimerization facilitate pore enlargement required to release large mitochondrial intermembrane space proteins. Apoptotic Bax oligomers permeabilize the mitochondrial outer membrane. Structural analyses and modeling of Bax interactions at mitochondria show that BH3-in-groove dimerization on membranes initiates the pore assembly, which is followed by helix 9 dimerization-mediated expansion.
AB - Pro-apoptotic Bax induces mitochondrial outer membrane permeabilization (MOMP) by forming oligomers through a largely undefined process. Using site-specific disulfide crosslinking, compartment-specific chemical labeling, and mutational analysis, we found that activated integral membrane Bax proteins form a BH3-in-groove dimer interface on the MOM surface similar to that observed in crystals. However, after the α5 helix was released into the MOM, the remaining interface with α2, α3, and α4 helices was rearranged. Another dimer interface was formed inside the MOM by two intersected or parallel α9 helices. Combinations of these interfaces generated oligomers in the MOM. Oligomerization was initiated by BH3-in-groove dimerization, without which neither the other dimerizations nor MOMP occurred. In contrast, α9 dimerization occurred downstream and was required for release of large but not small proteins from mitochondria. Moreover, the release of large proteins was facilitated by α9 insertion into the MOM and localization to the pore rim. Therefore, the BH3-in-groove dimerization on the MOM nucleates the assembly of an oligomeric Bax pore that is enlarged by α9 dimerization at the rim. Synopsis Apoptotic Bax oligomers permeabilize the mitochondrial outer membrane. Structural analyses and modeling of Bax interactions at mitochondria show that BH3-in-groove dimerization on membranes initiates the pore assembly, which is followed by helix 9 dimerization-mediated expansion. Bax protein oligomerization initiates with helices α2-α5 forming a BH3-in-groove dimer interface on the membrane surface. The BH3-in-groove dimer interface is rearranged after α5 insertion into the membrane. α9 helices from neighboring Bax molecules form another dimer interface inside the membrane linking the BH3-in-groove dimers to higher order oligomers. α9 insertion and dimerization facilitate pore enlargement required to release large mitochondrial intermembrane space proteins. Apoptotic Bax oligomers permeabilize the mitochondrial outer membrane. Structural analyses and modeling of Bax interactions at mitochondria show that BH3-in-groove dimerization on membranes initiates the pore assembly, which is followed by helix 9 dimerization-mediated expansion.
KW - Apoptosis/Bcl-2 proteins
KW - membrane permeabilization
KW - mitochondrial membranes
KW - oligomerization
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U2 - 10.15252/embj.201591552
DO - 10.15252/embj.201591552
M3 - Article
C2 - 26702098
AN - SCOPUS:84955390719
SN - 0261-4189
VL - 35
SP - 208
EP - 236
JO - EMBO Journal
JF - EMBO Journal
IS - 2
ER -