Peptides derived from apoptotic bax and bid reproduce the poration activity of the parent full-length proteins
Peptides derived from apoptotic bax and bid reproduce the poration activity of the parent full-length proteins
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DOI：
10.1529/biophysj.104.058008
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发表时间：
2005-06-01
影响因子：
3.4
通讯作者：
Salgado, J
中科院分区：
文献类型：
--
作者：
García-Sáez, AJ;Coraiola, M;Salgado, J
Bax和Bid是Bcl-2家族的促凋亡蛋白，其调节促凋亡因子从线粒体的释放。虽然它们组成性地定位于细胞质中，但它们的凋亡功能在线粒体外膜处发挥，并且与它们形成跨双层孔的能力有关。在这里，我们报告的穿孔活性的片段，从这两种蛋白质，含有第一个α-螺旋的大肠杆菌素样疏水发夹（α-螺旋5的Bax和α-螺旋6的投标）。这两种肽容易结合到合成的脂质囊泡，其中它们主要采用α-螺旋结构并诱导释放捕获的钙黄绿素。在平面脂质膜中，它们形成离子传导通道，在α-衍生肽的情况下，其特征在于两阶段模式、大电导率和脂质电荷依赖性离子选择性。这些功能，连同内在的脂质曲率的影响上的穿孔活性和存在的两个螺旋伸展的不同方向的膜结合肽，表明它形成混合的环状结构的peptidic/peptidic孔。相比之下，测定的Bid片段显示出明显不同的行为，其特征在于在平面脂质双层中形成离散的阶梯状通道，正如预期的由一束螺旋内衬的肽孔。
Bax and Bid are proapoptotic proteins of the Bcl-2 family that regulate the release of apoptogenic factors from mitochondria. Although they localize constitutively in the cytoplasm, their apoptotic function is exerted at the mitochondrial outer membrane, and is related to their ability to form transbilayer pores. Here we report the poration activity of fragments from these two proteins, containing the first alpha-helix of a colicinlike hydrophobic hairpin (alpha-helix 5 of Bax and alpha-helix 6 of Bid). Both peptides readily bind to synthetic lipid vesicles, where they adopt predominantly alpha-helical structures and induce the release of entrapped calcein. In planar lipid membranes they form ion conducting channels, which in the case of the Bax-derived peptide are characterized by a two-stage pattern, a large conductivity and lipid-charge-dependent ionic selectivity. These features, together with the influence of intrinsic lipid curvature on the poration activity and the existence of two helical stretches of different orientations for the membrane-bound peptide, suggest that it forms mixed lipidic/peptidic pores of toroidal structure. In contrast, the assayed Bid fragment shows a markedly different behavior, characterized by the formation of discrete, steplike channels in planar lipid bilayers, as expected for a peptidic pore lined by a bundle of helices.