Roles of Leu28 side chain intercalation in the interaction between Cren7 and DNA----中国科学院微生物研究所

科研成果

论文题目:	Roles of Leu28 side chain intercalation in the interaction between Cren7 and DNA
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:	http://www.biochemj.org/content/474/10/1727
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.