After Embedding in Membranes Antiapoptotic Bcl-XL Protein Binds Both Bcl-2 Homology Region 3 and Helix 1 of Proapoptotic Bax Protein to Inhibit Apoptotic Mitochondrial Permeabilization
After Embedding in Membranes Antiapoptotic Bcl-XL Protein Binds Both Bcl-2 Homology Region 3 and Helix 1 of Proapoptotic Bax Protein to Inhibit Apoptotic Mitochondrial Permeabilization
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DOI：
10.1074/jbc.m114.552562
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发表时间：
2014-04-25
影响因子：
4.8
通讯作者：
Lin, Jialing
中科院分区：
文献类型：
--
作者：
Ding, Jingzhen;Mooers, Blaine H. M.;Lin, Jialing
背景：Bcl-XL在线粒体结合Bax，抑制Bax寡聚化和凋亡。结果：Bcl-XLBax异源二聚体锚定在细胞膜上，由刚性的螺旋槽界面和柔性的螺旋二聚体界面形成。结论：两个接口同样有助于抑制Bax所需的异二聚体稳定性。重要性：这种新型的蛋白质-蛋白质相互作用稳定了膜结合的异源二聚体，这是凋亡调控的关键。Bcl-XL与Bax结合，抑制凋亡过程中线粒体外膜透化（MOMP）所需的Bax寡聚化。Bcl-XL如何在膜中与Bax结合尚不清楚。在这里，我们研究了Bcl-XLBax复合物中形成的Bcl-XLBax复合物的结构组织，包括结合界面和膜拓扑结构，使用位点特异性交联，隔室特异性标记和计算建模。我们发现，一个异二聚体界面是由Bcl-XL的Bcl-2同源1-3（BH 1 -3）沟和Bax的BH 3螺旋之间的特异性相互作用形成的，如先前通过截短的Bcl-XL蛋白和Bax BH 3肽的晶体结构所定义的（蛋白质数据库条目3 PL 7）。我们还发现了一个新的界面中的异源二聚体形成的螺旋1区域的Bcl-XL和Bax之间的等效相互作用时，他们的螺旋轴是平行或反平行的取向。这两个接口位于胞浆侧的Bcl-XL，而螺旋9是嵌入在膜连同螺旋5，6和9的Bax。螺旋1螺旋1界面的形成部分取决于grooveBH 3界面的形成，因为后者界面中的点突变和添加ABT-737（一种结合grooveBH 3的模拟物）阻断了两个界面的形成。突变和ABT-737也阻止了Bcl-XL抑制Bax寡聚化和随后的MOMP，这表明在两个界面的相互作用有助于复合物的整体稳定性和功能性的结构组织代表了Bcl-XLBax复合物中的抗凋亡。
Background: Bcl-XL binds Bax at mitochondria, inhibiting Bax oligomerization and apoptosis. Results: Anchored in membranes, Bcl-XLBax heterodimer is formed from a rigid helix-in-groove interface plus a flexible helical dimer interface. Conclusion: Two interfaces contribute equally to the heterodimer stability required to inhibit Bax. Significance: This novel kind of protein-protein interaction stabilizes the membrane-bound heterodimer that is pivotal to apoptosis regulation.Bcl-XL binds to Bax, inhibiting Bax oligomerization required for mitochondrial outer membrane permeabilization (MOMP) during apoptosis. How Bcl-XL binds to Bax in the membrane is not known. Here, we investigated the structural organization of Bcl-XLBax complexes formed in the MOM, including the binding interface and membrane topology, using site-specific cross-linking, compartment-specific labeling, and computational modeling. We found that one heterodimer interface is formed by a specific interaction between the Bcl-2 homology 1-3 (BH1-3) groove of Bcl-XL and the BH3 helix of Bax, as defined previously by the crystal structure of a truncated Bcl-XL protein and a Bax BH3 peptide (Protein Data Bank entry 3PL7). We also discovered a novel interface in the heterodimer formed by equivalent interactions between the helix 1 regions of Bcl-XL and Bax when their helical axes are oriented either in parallel or antiparallel. The two interfaces are located on the cytosolic side of the MOM, whereas helix 9 of Bcl-XL is embedded in the membrane together with helices 5, 6, and 9 of Bax. Formation of the helix 1helix 1 interface partially depends on the formation of the grooveBH3 interface because point mutations in the latter interface and the addition of ABT-737, a groove-binding BH3 mimetic, blocked the formation of both interfaces. The mutations and ABT-737 also prevented Bcl-XL from inhibiting Bax oligomerization and subsequent MOMP, suggesting that the structural organization in which interactions at both interfaces contribute to the overall stability and functionality of the complex represents antiapoptotic Bcl-XLBax complexes in the MOM.