Dewson Grant, Kratina Tobias, Sim Huiyan W, Puthalakath Hamsa, Adams Jerry M, Colman Peter M, Kluck Ruth M
Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, Victoria 3050, Australia.
Mol Cell. 2008 May 9;30(3):369-80. doi: 10.1016/j.molcel.2008.04.005.
The Bcl-2 relative Bak is thought to drive apoptosis by forming homo-oligomers that permeabilize mitochondria, but how it is activated and oligomerizes is unclear. To clarify these pivotal steps toward apoptosis, we have characterized multiple random loss-of-function Bak mutants and explored the mechanism of Bak conformation change during apoptosis. Single missense mutations located to the alpha helix 2-5 region of Bak, with most altering the BH3 domain or hydrophobic groove (BH1 domain). Loss of function invariably corresponded to impaired ability to oligomerize. An essential early step in Bak activation was shown to be exposure of the BH3 domain, which became reburied in dimers. We demonstrate that oligomerization involves insertion of the BH3 domain of one Bak molecule into the groove of another and may produce symmetric Bak dimers. We conclude that this BH3:groove interaction is essential to nucleate Bak oligomerization, which in turn is required for its proapoptotic function.
Bcl-2相关蛋白Bak被认为通过形成使线粒体通透性增加的同型寡聚体来驱动细胞凋亡，但其激活和寡聚化的机制尚不清楚。为了阐明这些通向细胞凋亡的关键步骤，我们对多个随机功能丧失的Bak突变体进行了表征，并探索了细胞凋亡过程中Bak构象变化的机制。单个错义突变位于Bak的α螺旋2-5区域，大多数突变改变了BH3结构域或疏水凹槽（BH1结构域）。功能丧失总是与寡聚化能力受损相对应。Bak激活的一个关键早期步骤被证明是BH3结构域的暴露，该结构域在二聚体中重新被掩埋。我们证明寡聚化涉及一个Bak分子的BH3结构域插入另一个分子的凹槽中，并可能产生对称的Bak二聚体。我们得出结论，这种BH3：凹槽相互作用对于启动Bak寡聚化至关重要，而Bak寡聚化反过来又是其促凋亡功能所必需的。
