High precision solution structure of the C-terminal KH domain of heterogeneous nuclear ribonucleoprotein K, a c-myc transcription factor
High precision solution structure of the C-terminal KH domain of heterogeneous nuclear ribonucleoprotein K, a c-myc transcription factor
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DOI：
10.1006/jmbi.1999.2818
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发表时间：
1999-06-18
影响因子：
5.6
通讯作者：
Tjandra, N
中科院分区：
文献类型：
--
作者：
Baber, JL;Libutti, D;Tjandra, N
在其许多已报道的功能中，异质核核糖核蛋白（hnRNP）K是c-myc基因的转录因子，c-myc基因是调节细胞生长和分化的关键原癌基因。我们已经通过NMR光谱确定了hnRNP K的C-末端K-同源（KH）结构域的Gly 26-> Arg突变体的溶液结构。这是首次对hnRNP K的结构进行研究。主干剩余偶极耦合提供的信息与标准NOE衍生的距离约束有根本不同，用于提高结构质量。通过比较主链N-15 T-1/T-2比值与计算结构，实现了结构质量的独立评估。hnRNP K（KH 3）的C-末端KH模块被揭示为相对于三个α-螺旋堆叠的三链β-折叠，其中两个α-螺旋几乎平行于β-折叠的链。Gly 26--> Arg突变消除了单链DNA结合，而不改变蛋白质的整体折叠。这为KH 3可能的核苷酸结合位点提供了线索。β折叠的溶剂暴露侧似乎不太可能是蛋白质-核酸复合物形成的位点。这与早期的蛋白质-RNA复合物的主题相反，该复合物包含结构上类似于KH 3的蛋白质。我们建议，与核酸相互作用的KH 3的表面与牛乳头瘤病毒1 E2的双链DNA结合结构域的DNA相互作用的区域相当，其具有与KH 3类似的三维折叠。
Among it's many reported functions, heterogeneous nuclear ribonucleoprotein (hnRNP) K is a transcription factor for the c-myc gene, a proto-oncogene critical for the regulation of cell growth and differentiation. We have determined the solution structure of the Gly26 --> Arg mutant of the C-terminal K-homology (KH) domain of hnRNP K by NMR spectroscopy. This is the first structure investigation of hnRNP K. Backbone residual dipolar couplings, which provide information that is fundamentally different from the standard NOE-derived distance restraints, were employed to improve structure quality. An independent assessment of structure quality was achieved by comparing the backbone N-15 T-1/T-2 ratios to the calculated structures. The C-terminal KH module of hnRNP K (KH3) is revealed to be a three-stranded beta-sheet stacked against three alpha-helices, two of which are nearly parallel to the strands of the beta-sheet. The Gly26 --> Arg mutation abolishes single-stranded DNA binding without altering the overall fold of the protein. This provides a clue to possible nucleotide binding sites of KH3. It appears unlikely that the solvent-exposed side of the beta-sheet will be the site of protein-nucleic acid complex formation. This is in contrast to the earlier theme for protein-RNA complexes incorporating proteins structurally similar to KH3. We propose that the surface of KH3 that interacts with nucleic acid is comparable to the region of DNA interaction for the double-stranded DNA-binding domain of bovine papillomavirus-1 E2 that has a three-dimensional fold similar to that of KH3.