DNA structural deformations in the interaction of the controller protein C. AhdI with its operator sequence
DNA structural deformations in the interaction of the controller protein C. AhdI with its operator sequence
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DOI：
10.1093/nar/gkm129
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发表时间：
2007-04-01
影响因子：
14.9
通讯作者：
Kneale, G. G.
中科院分区：
文献类型：
--
作者：
Papapanagiotou, I.;Streeter, S. D.;Kneale, G. G.
控制蛋白，如C.AhdI，调节细菌限制性内切酶基因的表达，并通过延迟内切酶的转录，确保宿主DNA的甲基化先于限制。与C.AhdI结合的操纵子DNA序列由两个相邻的结合位点OL和O-R组成。用圆排列弯曲分析和圆二色谱研究了C.AhdI与O-L和O-L+O-R的结合。Cd表明，当与C.AhdI结合时，DNA发生了相当大的扭曲。结合到一个或两个位置形成二聚体和四聚体络合物使278 nm处的CD信号分别增加40%和80%，在这两个位置表现出相同的局部失真。相比之下，DNA弯曲分析给出了二聚体和四聚体配合物相似的弯曲角(分别为47和388)。讨论了C.AhdI二聚体在四聚体复合体中的相对取向以及位于C蛋白结合位点中心的保守序列Py-A-T的结构作用。
Controller proteins such as C.AhdI regulate the expression of bacterial restriction-modification genes, and ensure that methylation of the host DNA precedes restriction by delaying transcription of the endonuclease. The operator DNA sequence to which C.AhdI binds consists of two adjacent binding sites, OL and O-R. Binding of C.AhdI to O-L and to O-L + O-R has been investigated by circular permutation DNA-bending assays and by circular dichroism (CD) spectroscopy. CD indicates considerable distortion to the DNA when bound by C. AhdI. Binding to one or two sites to form dimeric and tetrameric complexes increases the CD signal at 278 nm by 40 and 80% respectively, showing identical local distortion at both sites. In contrast, DNA-bending assays gave similar bend angles for both dimeric and tetrameric complexes (47 and 388, respectively). The relative orientation of C. AhdI dimers in the tetrameric complex and the structural role of the conserved Py-A-T sequences found at the centre of C-protein-binding sites are discussed.