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首页> 外文期刊>Journal of Molecular Biology >Conformation of the RNA polymerase II C-terminal domain: circular dichroism of long and short fragments.
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Conformation of the RNA polymerase II C-terminal domain: circular dichroism of long and short fragments.

机译：RNA聚合酶II C末端结构域的构象：长短片段的圆二色性。

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摘要

The C-terminal domain (CTD) of the largest subunit of RNA polymerase II consists of tandemly repeated copies of a heptapeptide with the Y(1)S(2)P(3)T(4)S(5)P(6)S(7) consensus sequence. This repeat contains two overlapping SPXX motifs that can adopt a beta-turn conformation. In addition, each CTD repeat contains the PXXP sequence characteristic of the left-handed helix of polyproline II (P(II)) found in SH3 domain ligands and the PXY sequence that is the target for WW domains. We have studied CTD fragments using circular dichroism (CD) to characterize the conformation of the CTD in water and in the hydrogen bond-promoting solvent trifluoroethanol (TFE). In water, an eight-repeat fragment is predominantly unordered, but at 32 degrees C has P(II) and beta-turn contents estimated to be about 15 % and less than 10 %, respectively. In 90 % TFE, the beta-turn fraction is estimated to be about 75 %, the remainder being unordered and P(II) conformations. The Tyr side-chains are ordered to a significant extent in 90 % TFE. Replacement of the fully conserved Pro residues by alpha-aminoisobutyric acid leads to a large increase in beta-turn. Replacement of Ser2 by Ala does not substantially alter the CTD conformation in water or TFE. Ser5 replacement by Ala increases the P(II) content in water and affects the conformation in TFE-rich solutions. Phosphorylation of Ser2 and Ser5 has little effect in water, but Ser2 affects the conformation in TFE-rich solution in much the same way as Ser5-->Ala substitution. The CD of the full-length murine CTD in water is similar to that of the eight-repeat fragment, indicating little difference in conformation with increasing chain length beyond eight repeats. The roles of P(II) and beta-turn in the interaction of CTD with its target proteins (mediator and RNA-processing components) are discussed. The most likely interactions are between P(II) and WW or SH3 domains, or with some unknown P(II)-binding motif. Copyright 2000 Academic Press.
机译：RNA聚合酶II最大亚基的C末端结构域（CTD）由具有Y（1）S（2）P（3）T（4）S（5）P（6）的七肽的串联重复副本组成S（7）共有序列。此重复序列包含两个重叠的SPXX图案，可以采用β-转角构象。此外，每个CTD重复序列均包含在SH3结构域配体中发现的聚脯氨酸II（P（II））左旋螺旋的PXXP序列特征，以及作为WW结构域靶标的PXY序列。我们已经使用圆二色性（CD）研究了CTD片段，以表征CTD在水和氢键促进溶剂三氟乙醇（TFE）中的构象。在水中，一个八重复片段主要是无序的，但是在32摄氏度时，P（II）和β-转角含量分别约为15％和小于10％。在90％的TFE中，β转角分数估计约为75％，其余为无序和P（II）构象。 Tyr侧链在90％TFE中有序排列。用α-氨基异丁酸替换完全保守的Pro残基会导致β转换大大增加。用Ala取代Ser2不会在水中或TFE中显着改变CTD构象。用Ala替代Ser5会增加水中的P（II）含量，并影响富含TFE的溶液中的构象。 Ser2和Ser5的磷酸化在水中几乎没有影响，但是Ser2对富含TFE的溶液中的构象的影响与Ser5-> Ala取代的影响几乎相同。全长鼠类CTD在水中的CD与八重复片段的CD相近，表明构象差异几乎没有，随着链长超过八个重复而增加。讨论了P（II）和β-turn在CTD与靶蛋白（介体和RNA加工成分）相互作用中的作用。最可能的相互作用是在P（II）与WW或SH3域之间，或具有某些未知的P（II）结合基序。版权所有2000学术出版社。

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