Wang Youli, Cao Rong, Liu Dongxiang, Chervin Adam, Yuan Jian, An Jing, Huang Ziwei
Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Biochem Biophys Res Commun. 2007 Oct 5;361(4):1006-11. doi: 10.1016/j.bbrc.2007.07.122. Epub 2007 Jul 31.
BH4 domain is critical for the anti-apoptotic functions of Bcl-2 and Bcl-x(L) and their binding abilities with other members of the Bcl-2 family. The cleavage of the BH4 domain in Bcl-x(L) and Bcl-2 by caspase 1 or 3 converts the anti-apoptotic Bcl-x(L) and Bcl-2 into pro-apoptotic proteins that potently induce apoptosis. Herein, we report that recombinant Bcl-x(L) proteins without N-terminal 61 residues, His(6)-NDelta61-Bcl-x(L)-CDelta21 and NDelta61-Bcl-x(L)-CDelta21, form oligomers in solution, whereas Bcl-x(L)-CDelta21 exists as a monomer. The oligomerization of the truncated proteins is independent of protein-lipid interaction, protein concentration or the ion strength of the solution. Circular dichroism spectrum shows a significant decrease in the content of alpha-helices upon deletion of N-terminal residues. NDelta61-Bcl-x(L)-CDelta21 also loses its heterodimerization capability with the BH3 peptide derived from Bak. This newly acquired property might be linked to its ability to induce apoptosis in cells.
BH4结构域对于Bcl-2和Bcl-x(L)的抗凋亡功能及其与Bcl-2家族其他成员的结合能力至关重要。半胱天冬酶1或3对Bcl-x(L)和Bcl-2中BH4结构域的切割将抗凋亡的Bcl-x(L)和Bcl-2转化为能有效诱导凋亡的促凋亡蛋白。在此，我们报道，缺失N端61个残基的重组Bcl-x(L)蛋白，即His(6)-NΔ61-Bcl-x(L)-CΔ21和NΔ61-Bcl-x(L)-CΔ21，在溶液中形成寡聚体，而Bcl-x(L)-CΔ21以单体形式存在。截短蛋白的寡聚化与蛋白质-脂质相互作用、蛋白质浓度或溶液的离子强度无关。圆二色光谱显示，缺失N端残基后α螺旋含量显著降低。NΔ61-Bcl-x(L)-CΔ21也失去了与源自Bak的BH3肽形成异源二聚体的能力。这种新获得的特性可能与其在细胞中诱导凋亡的能力有关。
