BAX Activation: Mutations Near Its Proposed Non-canonical BH3 Binding Site Reveal Allosteric Changes Controlling Mitochondrial Association
BAX Activation: Mutations Near Its Proposed Non-canonical BH3 Binding Site Reveal Allosteric Changes Controlling Mitochondrial Association
复制标题
DOI：
10.1016/j.celrep.2019.03.040
复制
发表时间：
2019-04-09
期刊：
影响因子：
8.8
通讯作者：
Adams, Jerry M.
中科院分区：
文献类型：
--
作者：
Dengler, Michael A.;Robin, Adeline Y.;Adams, Jerry M.
为了引发细胞凋亡，BAX 从惰性胞浆单体转变为可透化线粒体外膜 (MOM) 的同源寡聚物。一个长期存在的谜团是，BH3 结构域显然不仅通过其规范凹槽激活 BAX，还通过涉及螺旋 α 1 和 α 6 的拟议位点激活 BAX。我们的诱变研究表明，寡聚化等后期步骤需要通过凹槽激活，但可能不需要 MOM 关联等早期步骤激活。相反，α1 或α6 阻塞和丙氨酸诱变扫描表明这些螺旋参与了 BAX 激活的早期阶段。 α1和α6突变降低了BH3结合，改变了BAX构象，并减少了其MOM易位和整合；他们暴露的 BAX α 1-α 2 环以变构方式将其 α 9 膜锚定在凹槽中。 α 6 突变体的晶体结构揭示了额外的变构效应。结果表明，α1 和 α6 区域驱动 MOM 缔合和整合，而凹槽结合有利于后续的寡聚化步骤。
To elicit apoptosis, BAX metamorphoses from an inert cytosolic monomer into homo-oligomers that permeabilize the mitochondrial outer membrane (MOM). A long-standing puzzle is that BH3 domains apparently activate BAX by not only its canonical groove but also a proposed site involving helices alpha 1 and alpha 6. Our mutagenesis studies reveal that late steps like oligomerization require activation through the groove but probably not earlier steps like MOM association. Conversely, alpha 1 or alpha 6 obstruction and alanine mutagenesis scanning implicate these helices early in BAX activation. The alpha 1 and alpha 6 mutations lowered BH3 binding, altered the BAX conformation, and reduced its MOM translocation and integration; their exposure of the BAX alpha 1-alpha 2 loop allosterically sequestered its alpha 9 membrane anchor in the groove. The crystal structure of an alpha 6 mutant revealed additional allosteric effects. The results suggest that the alpha 1 and alpha 6 region drives MOM association and integration, whereas groove binding favors subsequent steps toward oligomerization.