Department of Chemistry and Biochemistry, Southern Illinois University Carbondale, Carbondale, Illinois, USA.
Protein Sci. 2021 May;30(5):1072-1080. doi: 10.1002/pro.4053. Epub 2021 Mar 12.
Mitochondrial outer membrane permeabilization, which is a critical step in apoptosis, is initiated upon transmembrane insertion of the C-terminal α-helix (α9) of the proapoptotic Bcl-2 family protein BAX. The isolated α9 fragment (residues 173-192) is also competent to disrupt model membranes, and the structures of its membrane-associated oligomers are of interest in understanding the potential roles of this sequence in apoptosis. Here, we used ultrafast two-dimensional infrared (2D IR) spectroscopy, thioflavin T binding, and transmission electron microscopy to show that the synthetic BAX α9 peptide (α9p) forms amyloid aggregates in aqueous environments and on the surfaces of anionic small unilamellar vesicles. Its inherent amyloidogenicity was predicted by sequence analysis, and 2D IR spectra reveal that vesicles modulate the β-sheet structures of insoluble aggregates, motivating further examination of the formation or suppression of BAX amyloids in apoptosis.
线粒体外膜通透性的开启是细胞凋亡的关键步骤，这一过程起始于促凋亡 Bcl-2 家族蛋白 Bax 的 C 端 α-螺旋（α9）跨膜插入。分离的 α9 片段（残基 173-192）也有能力破坏模型膜，而其膜相关寡聚物的结构对于理解该序列在凋亡中的潜在作用很有意义。在这里，我们使用超快二维红外（2D IR）光谱、硫黄素 T 结合和透射电子显微镜表明，合成的 Bax α9 肽（α9p）在水相环境中和阴离子小单层囊泡的表面形成淀粉样聚集物。序列分析预测了其固有的淀粉样特性，二维红外光谱揭示了囊泡调节不溶性聚集物的β-折叠结构，这促使我们进一步研究凋亡中 Bax 淀粉样纤维的形成或抑制。
