STRUCTURE/FUNCTION STUDIES OF GLUCOCORTICOID RECEPTOR

缺乏对其主要反活化结构域（AF1）结构的了解阻碍了对糖皮质激素受体功能机制的充分理解。据推测，AF1直接或通过中间蛋白与蛋白质的“转录机制”复合物相互作用。这需要蛋白质和产生它们的结构之间的表面对表面的相互作用。然而，当作为重组蛋白单独表达时，AR显示很少或没有结构，并且与少数此类蛋白结合较弱。我们已经进行了两项令人兴奋的观察，为了解AF1如何获得其假定功能所需的结构以及发现其天然结合伙伴提供了令人兴奋的希望。首先，我们发现在渗透物氧化三甲胺（TMAO）存在的情况下，人类GR的AF1获得了类似天然的结构，并显示出与某些其他蛋白质的结合大大增强。我们将使用TMAO和其他渗透物来研究AF1的结构并寻找其结合伙伴。其次，我们已经证明，当含有AF1和DNA结合结构域的GR双结构域片段与其同源DNA结合位点结合时，AR似乎获得了结构并能够结合某些其他蛋白质。在这个项目中，我们将确定控制这一事件的蛋白质和DNA参数。我们将比较两种技术发现的AF1结构和蛋白质结合伙伴。在我们所采用的条件下，其中一种核蛋白与AF1结合，似乎是核受体辅助激活因子蛋白家族的成员。使用的方法将包括圆二色性、本征荧光发射光谱、肽图谱、蛋白质的热力学严格研究：DNA结合核磁共振和如果获得晶体，x射线衍射。

Lack of knowledge of the structure of its major transactivation domain (AF1) has hampered full understanding of the mechanism by which the glucocorticoid receptor functions. It is presumed that AF1 interacts directly, or through intermediary proteins, with the "transcription machinery" complex of proteins. This requires surface-to-surface interactions between proteins and the structure to produce them. When expressed separately as a recombinant protein, however, AR displays little or no structure and binds weakly at best with a few such proteins. We have made two observations that offer exciting promise for understanding how AF1 obtains the structure necessary for its presumed function and for discovering its natural binding partners. First, we found that in the presence of an osmolyte, trimethylamine oxide (TMAO), the AF1 of the human GR acquires native-like structure and shows greatly enhanced binding to certain other proteins. We will use TMAO and other osmolytes to study the structure of AF1 and to find its binding partners. Second, we have shown that when a two-domain fragment of the GR containing AF1 and the DNA-binding domain is bound to its cognate DNA binding site, AR seems to acquire structure and be able to bind certain other proteins. In this project, we will determine the protein and DNA parameters that control this event. We will compare the AF1 structure and the protein binding partners uncovered by the two techniques. One of the nuclear proteins shown to bind AF1 under the conditions we employ appears to be a member of the nuclear receptor co- activator family of proteins. Methods used will include circular dichroism, intrinsic fluorescence emission spectroscopy, peptide mapping, thermodynamically rigorous studies of protein:DNA binding NMR and if crystals are obtained, X-ray diffraction.