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首页> 外文期刊>Biochemistry >Conformational Changes in the Nucleosome Followed by the Selective Accessibility of Histone Glutamines in the Transglutaminase Reactoin: Effects of Ionic Strength
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Conformational Changes in the Nucleosome Followed by the Selective Accessibility of Histone Glutamines in the Transglutaminase Reactoin: Effects of Ionic Strength

机译：核糖体的构象变化，然后在转谷氨酰胺反应蛋白中组蛋白谷氨酰胺的选择性可及性：离子强度的影响

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Transglutaminases, the enzymes that catalyze the acyl-transfer reaction between glutamine and primary amines, have been used to introduce probes into proteins in order to perform structural studies using physical techniques. Here we use an original approach in which the increasing accessibility of the glutamines of core histones to TGase is used to monitor the salt-induced conformational changes of the nucleosome. The rationale of this strategy is that the accessibility of a glutamine to trans glutaminase depends on the blockage due to the presence of either other histones or DNA. At low ionic strength, only glutamines on the N-terminal tails of H2B and H3 are labeled with monodansylcadaverine when core particles are incubated with trans glutaminase. The partial unfolding that occurs when going to higher ionic strength values results in an increase in the number of reactive glutamines up to a maximum value of 16 per nucleosome. Labeling of some residues (e.g., Glnl04 and Glnl12 of H2A) requires the unwinding of DNA and the dissociation of the H2A-H2B dimmers. Gln76 of H3 is labeled in the H3-H4 tetramer only when the H2A -H2B dimmers are dissociated. Interestingly, the labeling of Gln95 of H2B exclusively _depends on the unwinding of DNA. The accurate analysis of these results indicates that the ionic-dependent unwinding of the DNA may occur following a two-state model.
机译：转谷氨酰胺酶（一种催化谷氨酰胺和伯胺之间的酰基转移反应的酶）已用于将探针引入蛋白质中，以便使用物理技术进行结构研究。在这里，我们使用一种原始方法，其中核心组蛋白的谷氨酰胺对TGase的增加可及性被用来监测盐诱导的核小体构象变化。该策略的基本原理是，由于存在其他组蛋白或DNA，谷氨酰胺转谷氨酰胺酶的可及性取决于阻断作用。在低离子强度下，当核心颗粒与反式谷氨酰胺酶一起孵育时，只有H2B和H3的N末端尾巴上的谷氨酰胺被单丹磺酰尸胺标记。当达到更高的离子强度值时发生的部分展开会导致反应性谷氨酰胺的数量增加，最多达到每个核小体16的最大值。标记一些残基（例如H2A的Gln104和Gln12）需要解开DNA并解离H2A-H2B二聚体。仅当H2A -H2B二聚体解离时，H3的Gln76才在H3-H4四聚体中标记。有趣的是，H2B的Gln95标记完全取决于DNA的解链。对这些结果的准确分析表明，遵循两态模型可能会发生DNA的离子依赖性解旋。

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