The LEF-1 high-mobility group domain undergoes a disorder-to-order transition upon formation of a complex with cognate DNA
The LEF-1 high-mobility group domain undergoes a disorder-to-order transition upon formation of a complex with cognate DNA
复制标题
DOI：
10.1021/bi049591m
复制
发表时间：
2004-07-13
期刊：
影响因子：
2.9
通讯作者：
Wright, PE
中科院分区：
文献类型：
--
作者：
Love, JJ;Li, X;Wright, PE
淋巴增强因子-1(Lef-1)是高迁移率族(HMG)蛋白家族中的一员，是一种结构转录因子。在与其同源DNA的复合体中，Lef-1结构域是高度有序的，其核磁共振谱具有折叠的球状蛋白的特征。相反，未复合的蛋白质表现出实质性的构象异质性的核磁共振证据，尽管圆二色谱表明DNA结合态的大部分α螺旋二级结构被保留在游离蛋白质中。对游离的Lef-1结构域进行的异核核磁共振实验表明，HMG结构域的螺旋II和螺旋III是折叠的，尽管螺旋III相对于DNA结合的蛋白质在其C末端被截断。螺旋II和螺旋III之间的主要疏水核心似乎已经形成，但靠近螺旋III C末端的次要核心在游离蛋白中是非结构化的。螺旋I的主干共振是检测不到的，可能是由于微秒到毫秒时间尺度上两个或更多构象之间的波动导致交换展宽的结果。在圆二色谱的基础上，多肽的这一区域似乎采用螺旋结构，但在没有DNA的情况下螺旋并不完全稳定。这些发现认为，在结合、弯曲和扭曲DNA之前，Lef-1的HMG结构域以分段无序或部分折叠的状态存在。在复合体形成后，蛋白质结构域经历与DNA的协同折叠转变为高度有序和良好折叠的状态。
Lymphoid enhancer-binding factor-1 (LEF-1), a member of the high-mobility group (HMG) family of proteins, functions as an architectural transcription factor. In complex with its cognate DNA, the LEF-1 domain is highly ordered, and its NMR spectra are characteristic of a folded globular protein. In contrast, the uncomplexed protein exhibits NMR evidence of substantial conformational heterogeneity, although circular dichroism spectra indicate that much of the alpha-helical secondary structure of the DNA-bound state is retained in the free protein. Heteronuclear NMR experiments performed on the free LEF-1 domain reveal that helix II and helix III of the HMG domain are folded, although helix III is truncated at its C-terminal end relative to the DNA-bound protein. The major hydrophobic core between helices II and III appears to be formed, but the minor core near the C-terminus of helix III is unstructured in the free protein. Backbone resonances of helix I are undetectable, probably as a result of exchange broadening due to fluctuations between two or more conformations on a microsecond-to-millisecond time scale. On the basis of the circular dichroism spectrum, this region of the polypeptide appears to adopt helical structure but the helix is not fully stabilized in the absence of DNA. These findings argue that, prior to binding, bending, and distorting DNA, the HMG domain of LEF-1 exists in a segmentally disordered or partially folded state. Upon complex formation, the protein domain undergoes a cooperative folding transition with DNA to a highly ordered and well-folded state.