Van Hoy M, Leuther K K, Kodadek T, Johnston S A
Department of Chemistry and Biochemistry, University of Texas, Austin 78712.
Cell. 1993 Feb 26;72(4):587-94. doi: 10.1016/0092-8674(93)90077-4.
The most common class of activation domains, the so-called acidic activators, has been proposed either to adopt an amphipathic alpha-helical structure or to exist as unstructured "acid blobs." However, genetic analysis of an acidic activation domain in the yeast GAL4 protein has suggested that the structure of the activation region is a beta sheet. To distinguish between these models, we conducted a biophysical analysis of peptides corresponding to the yeast GAL4 and GCN4 acidic activation domains. Circular dichroism spectroscopy shows that the peptides are not alpha helical, but that they can undergo a transition to a structure that is almost 100% beta sheet in character in slightly acidic solution. We also show that the artificial acidic activator AH has structural properties that are markedly different from the natural GAL4 and GCN4 domains and does not adopt a beta-rich structure at reduced pH.
最常见的一类激活结构域，即所谓的酸性激活剂，有人提出其要么采用两亲性α螺旋结构，要么以无结构的“酸性团块”形式存在。然而，对酵母GAL4蛋白中一个酸性激活结构域的基因分析表明，激活区域的结构是β折叠。为了区分这些模型，我们对与酵母GAL4和GCN4酸性激活结构域相对应的肽段进行了生物物理分析。圆二色光谱表明，这些肽段不是α螺旋，但在微酸性溶液中它们可以转变为一种几乎100%为β折叠性质的结构。我们还表明，人工酸性激活剂AH具有与天然GAL4和GCN4结构域明显不同的结构特性，并且在pH降低时不会形成富含β折叠的结构。
