Insights into the interaction between Cren7 and DNA: the role of loop β3-β4
Insights into the interaction between Cren7 and DNA: the role of loop β3-β4
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DOI：
10.1007/s00792-014-0725-y
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发表时间：
2015-03-01
期刊：
影响因子：
2.9
通讯作者：
Huang, Li
中科院分区：
文献类型：
--
作者：
Zhang, Zhenfeng;Gong, Yong;Huang, Li
硫化叶菌合成大量的小染色质蛋白Cren 7和Sul 7 d。这两种蛋白质具有整体结构相似性，但在β 3链和β 4链之间的DNA结合区域明显不同。虽然Sul 7 d具有两个氨基酸残基的铰链，但Cren 7在该区域中含有灵活的七个残基环（环β 3-β 4）。在这里，我们报告了环β 3-β 4在Cren 7与双链DNA相互作用中的作用。我们表明，所有残基与一个大的侧链上的环，即，Pro30、Lys 31、Arg 33和Lys 34对Cren 7与DNA的结合有显著贡献。这三种碱性氨基酸以残基数目依赖的方式影响Cren 7限制负DNA超螺旋的能力。已确定突变Cren 7蛋白（GR）与8-bp dsDNA之间的复合物的晶体结构，其中环β 3-β 4被两个残基（Gly和Arg）取代以模拟Sul 7 d中相应位置处的铰链。GR-DNA和Cren 7-DNA复合物之间的结构比较表明，GR在DNA结合大小、对DNA大沟宽度的影响和DNA弯曲模式方面更类似于Sul 7 d而不是Cren 7。然而，GR诱导的DNA曲率小于Sul 7 d。我们的研究结果表明，Cren 7和Sul 7 d包装染色体DNA在一个略有不同的方式，大概允许不同的染色体可及性蛋白质在DNA交易中发挥作用。
Sulfolobus synthesizes large amounts of small chromatin proteins Cren7 and Sul7d. The two proteins share overall structural similarity, but differ distinctly in the DNA-binding region between beta 3- and beta 4-strands. While Sul7d possesses a hinge of two amino acid residues, Cren7 contains a flexible seven-residue loop (loop beta 3-beta 4) in the region. Here, we report the role of loop beta 3-beta 4 in the interaction of Cren7 with duplex DNA. We show that all residues with a large side chain on the loop, i.e., Pro30, Lys31, Arg33 and Lys34, contributed significantly to the binding of Cren7 to DNA. The three basic amino acids affected the ability of Cren7 to constrain negative DNA supercoils in a residue number-dependent manner. The crystal structure of a complex between a mutant Cren7 protein (GR) with loop beta 3-beta 4 replaced by two residues (Gly and Arg) to mimic the hinge at the corresponding position in Sul7d and an 8-bp dsDNA has been determined. Structural comparison between the GR-DNA and Cren7-DNA complexes shows that GR resembles Sul7d more than Cren7 in DNA-binding size and in the effect on the width of the major groove of DNA and the pattern of DNA bending. However, GR induces smaller DNA curvature than Sul7d. Our results suggest that Cren7 and Sul7d package chromosomal DNA in a slightly different fashion, presumably permitting different chromosomal accessibility by proteins functioning in DNA transactions.