Antonsson B, Montessuit S, Lauper S, Eskes R, Martinou J C
Serono Pharmaceutical Research Institute, Ares-Serono International S.A., 14, chemin des Aulx, CH-1228 Plan-les Ouates, Geneva, Switzerland.
Biochem J. 2000 Jan 15;345 Pt 2(Pt 2):271-8.
Bax is a Bcl-2-family protein with pro-apoptotic activity that can form channels in lipid membranes. The protein has been shown to trigger cytochrome c release from mitochondria both in vitro and in vivo. Recombinant human Bax isolated in the presence of detergent was found to be present as an oligomer with an apparent molecular mass of approx. 160000 Da on gel filtration. When Bax was isolated in the absence of detergent the purified protein was monomeric with an apparent molecular mass of 22000 Da. Bax oligomers formed channels in liposomes and triggered cytochrome c release from isolated mitochondria, whereas monomeric Bax was inactive in both respects. Incubation of the monomeric Bax with 2% octyl glucoside induced formation of oligomers that displayed channel-forming activity in liposomes and triggered cytochrome c release from mitochondria. Triton X-100, Nonidet P-40 and n-dedecyl maltoside also activated monomeric Bax, whereas CHAPS had no activating effect. In cytosolic extracts from mouse liver, Bax migrated at a molecular mass of 24000 Da on gel filtration, whereas after incubation of the cytosol with 2% octyl glucoside Bax migrated at approximately 140000 Da. These results show that oligomeric Bax possesses channel-forming activity whereas monomeric Bax has no such activity.
Bax是一种具有促凋亡活性的Bcl-2家族蛋白，能够在脂质膜上形成通道。该蛋白已被证明在体外和体内均可触发细胞色素c从线粒体释放。在去污剂存在下分离得到的重组人Bax以一种表观分子量约为160000 Da的寡聚体形式存在于凝胶过滤中。当在没有去污剂的情况下分离Bax时，纯化后的蛋白为单体，表观分子量为22000 Da。Bax寡聚体在脂质体中形成通道，并触发细胞色素c从分离的线粒体中释放，而单体Bax在这两方面均无活性。将单体Bax与2%辛基葡糖苷一起孵育可诱导形成在脂质体中具有通道形成活性并能触发细胞色素c从线粒体释放的寡聚体。Triton X-100、Nonidet P-40和正十二烷基麦芽糖苷也能激活单体Bax，而CHAPS则没有激活作用。在小鼠肝脏的胞质提取物中，Bax在凝胶过滤中的分子量为24000 Da，而在用2%辛基葡糖苷孵育胞质后，Bax的迁移分子量约为140000 Da。这些结果表明，寡聚体Bax具有通道形成活性，而单体Bax则没有这种活性。
