Heimlich Gerd, McKinnon Alastair D, Bernardo Katussevani, Brdiczka Dieter, Reed John C, Kain Renate, Krönke Martin, Jürgensmeier Juliane M
Institute for Medical Microbiology, Immunology and Hygiene, University of Köln, 50935 Köln, Germany.
Biochem J. 2004 Feb 15;378(Pt 1):247-55. doi: 10.1042/BJ20031152.
The pro-apoptotic protein Bax plays a key role in the mitochondrial signalling pathway. Upon induction of apoptosis, Bax undergoes a conformational change and translocates to mitochondrial membranes, where it inserts and mediates the release of cytochrome c from the intermembrane space into the cytosol. However, the domains of Bax that are essential for the induction of cytochrome c release are still elusive. Therefore various Bax deletion mutants were generated and expressed in Escherichia coli. The proteins were then purified in order to delineate the function of the transmembrane domain, the BH3 (Bcl-2 homology 3) domain and the putative pore-forming alpha-helices-5 and -6. These proteins were used to analyse the mechanism of Bax-induced cytochrome c release from mitochondria. None of the Bax proteins caused cytochrome c release merely through physical perturbation of the mitochondrial outer membrane. The alpha-helices-5 and -6 of Bax were shown to mediate the insertion of the protein into mitochondrial membranes and to be essential for the cytochrome c -releasing activity of Bax. In contrast, neither the transmembrane domain nor a functional BH3 domain is required for the Bax-mediated release of cytochrome c from mitochondria.
促凋亡蛋白Bax在线粒体信号通路中起关键作用。在凋亡诱导时，Bax发生构象变化并转位至线粒体膜，在那里它插入并介导细胞色素c从膜间隙释放到细胞质中。然而，对于诱导细胞色素c释放至关重要的Bax结构域仍不清楚。因此，构建了各种Bax缺失突变体并在大肠杆菌中表达。然后纯化这些蛋白质，以阐明跨膜结构域、BH3（Bcl-2同源结构域3）结构域以及假定的形成孔道的α-螺旋5和α-螺旋6的功能。这些蛋白质用于分析Bax诱导细胞色素c从线粒体释放的机制。没有一种Bax蛋白仅通过线粒体外膜的物理扰动导致细胞色素c释放。已证明Bax的α-螺旋5和α-螺旋6介导该蛋白插入线粒体膜，并且对于Bax的细胞色素c释放活性至关重要。相反，Bax介导的细胞色素c从线粒体释放既不需要跨膜结构域也不需要功能性BH3结构域。
