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首页> 外文期刊>Biochemistry >Solution Structure of the Transcriptional Activation Domain of the Bacteriophage T4 Protein, MotA
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Solution Structure of the Transcriptional Activation Domain of the Bacteriophage T4 Protein, MotA

机译：噬菌体T4蛋白，MotA转录激活域的溶液结构。

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Bacteriophage T4 encodes a transcription factor, MotA, that binds to the —30 region of middle-mode promoters and activates transcription by host RNA polymerase. The crystal structure of the N-terminal domain of MotA (MotNF) revealed a six-helix domain in which the two C-terminal ct-helices mediate the formation of a dimer via a coiled-coil motif and hydrophobic interactions. This structure suggested that full-length MotA binds DNA as a dimer, but subsequent biochemical results have shown that a monomeric form of MotA binds DNA. In this study, gel filtration chromatography, dynamic light scattering, and NMR-based diffusion measurements show conclusively that MotNF is a monomer, and not a dimer, in solution. In addition, we have determined the monomeric solution structure of MotNF using NMR spectroscopy, and have compared this with the dimer structure observed in crystals. The core of the protein assumes the same helical conformation in solution and in crystals, but important differences are observed at the extreme C-terminus. In solution, helix c6 is followed by five disordered residues that probably link the N-terminal and C-terminal domains of MotA. In crystals, helix o.5 forms the dimer interface and is followed by a short sixth helix that further stabilizes the dimer configuration. The solution structure of MotNF supports the conclusion that MotA functions as a monomer, and suggests that the existence of the sixth helix in crystals is a consequence of crystal packing. Our work highlights the importance of investigating protein structures in both crystals and solution to fully understand biomolecular structure and to accurately deduce relationships between structure and function.
机译：噬菌体T4编码一个转录因子MotA，它与中型启动子的-30区结合并通过宿主RNA聚合酶激活转录。 MotA（MotNF）N末端域的晶体结构揭示了一个六螺旋域，其中两个C末端ct螺旋通过卷曲螺旋基序和疏水相互作用介导了二聚体的形成。这种结构表明全长MotA以二聚体的形式结合DNA，但随后的生化结果表明MotA的单体形式与DNA结合。在这项研究中，凝胶过滤色谱，动态光散射和基于NMR的扩散测量最终表明，MotNF是溶液中的单体，而不是二聚体。此外，我们使用NMR光谱法确定了MotNF的单体溶液结构，并将其与晶体中观察到的二聚体结构进行了比较。蛋白质的核心在溶液和晶体中均具有相同的螺旋构象，但在极端C端观察到重要的差异。在溶液中，螺旋c6之后是五个可能连接MotA的N端和C端结构域的残基。在晶体中，螺旋o.5形成二聚体界面，然后是短的第六螺旋，进一步稳定了二聚体构型。 MotNF的溶液结构支持MotA作为单体起作用的结论，并暗示晶体中第六螺旋的存在是晶体堆积的结果。我们的工作强调了研究晶体和溶液中蛋白质结构的重要性，以充分理解生物分子结构并准确推断结构与功能之间的关系。

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