Petros A M, Medek A, Nettesheim D G, Kim D H, Yoon H S, Swift K, Matayoshi E D, Oltersdorf T, Fesik S W
Pharmaceutical Discovery Division, Abbott Laboratories, Abbott Park, IL 60064, USA.
Proc Natl Acad Sci U S A. 2001 Mar 13;98(6):3012-7. doi: 10.1073/pnas.041619798. Epub 2001 Feb 27.
The structures of two isoforms of Bcl-2 that differ by two amino acids have been determined by NMR spectroscopy. Because wild-type Bcl-2 behaved poorly in solution, the structures were determined by using Bcl-2/Bcl-x(L) chimeras in which part of the putative unstructured loop of Bcl-2 was replaced with a shortened loop from Bcl-x(L). These chimeric proteins have a low pI compared with the wild-type protein and are soluble. The structures of the two Bcl-2 isoforms consist of 6 alpha-helices with a hydrophobic groove on the surface similar to that observed for the homologous protein, Bcl-x(L). Comparison of the Bcl-2 structures to that of Bcl-x(L) shows that although the overall fold is the same, there are differences in the structural topology and electrostatic potential of the binding groove. Although the structures of the two isoforms of Bcl-2 are virtually identical, differences were observed in the ability of the proteins to bind to a 25-residue peptide from the proapoptotic Bad protein and a 16-residue peptide from the proapoptotic Bak protein. These results suggest that there are subtle differences in the hydrophobic binding groove in Bcl-2 that may translate into differences in antiapoptotic activity for the two isoforms.
已通过核磁共振光谱法确定了两种相差两个氨基酸的Bcl-2亚型的结构。由于野生型Bcl-2在溶液中的表现不佳，因此通过使用Bcl-2/Bcl-x(L)嵌合体来确定结构，其中Bcl-2假定的无结构环的一部分被Bcl-x(L)的缩短环所取代。与野生型蛋白质相比，这些嵌合蛋白的等电点较低且可溶。两种Bcl-2亚型的结构由6个α螺旋组成，表面有一个疏水凹槽，类似于同源蛋白Bcl-x(L)的凹槽。将Bcl-2的结构与Bcl-x(L)的结构进行比较表明，尽管整体折叠相同，但结合凹槽的结构拓扑和静电势存在差异。尽管Bcl-2的两种亚型的结构几乎相同，但观察到这些蛋白质与促凋亡Bad蛋白的25个残基肽和促凋亡Bak蛋白的16个残基肽结合能力存在差异。这些结果表明，Bcl-2的疏水结合凹槽存在细微差异，这可能转化为两种亚型在抗凋亡活性上的差异。
