| 论文题目: | Roles of Leu28 side chain intercalation in the interaction between Cren7 and DNA |
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| 作者: | Zhang Zhenfeng, Zhao Mohan, Wang Li, Chen Yuanyuan, Dong Yuhui, Gong Yong, and Huang Li*. |
| 联系作者: | |
| 刊物名称: | Biochem J |
| 期: | |
| 卷: | 474 |
| 页: | 1727-1739 |
| 年份: | 2017 |
| 影响因子: | 4.116 |
| 论文下载: | 下载地址 |
| 摘要: | Crenarchaeal chromatin protein Cren7 binds double-stranded DNA in the minor groove, introducing a sharp single-step DNA kink. The side chain of Leu28, a residue conserved among all Cren7 homologs, intercalates into the kinked DNA step. In the present study, we replaced Leu28 with a residue containing a hydrophobic side chain of different sizes (i.e. L28A, L28V, L28I, L28M and L28F). Both the stability of the Cren7-DNA complex and the ability of Cren7 to constrain DNA supercoils correlated well with the size of the intercalated side chain. Structural analysis shows that L28A induces a kink ( approximately 43 degrees ), nearly as sharp as that produced by wild-type Cren7 ( approximately 48 degrees ), in the bound DNA fragment despite the lack of side chain intercalation. In another duplex DNA fragment, L28F inserts a large hydrophobic side chain deep into the DNA step, but introduces a smaller kink ( approximately 39 degrees ) than that formed by the wild-type protein ( approximately 50 degrees ). Mutation of Leu28 into methionine yields two protein conformers differing in loop beta3-beta4 orientation, DNA-binding surface and DNA geometry in the protein-DNA structure. Our results indicate that side chain intercalation is not directly responsible for DNA kinking or bending by Cren7, but plays a critical role in the stabilization of the Cren7-DNA complex. In addition, the flexibility of loop beta3-beta4 in Cren7, as revealed in the crystal structure of L28M-DNA, may serve a role in the modulation of chromosomal organization and function in the cell. |
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