Summary information and primary citation

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DNA binding protein-DNA
X-ray (1.8 Å)
The crystal structure of cren7 mutant l28a in complex with dsDNA
Zhang Z, Zhao M, Wang L, Chen Y, Dong Y, Gong Y, Huang L (2017): "Roles of Leu28 side chain intercalation in the interaction between Cren7 and DNA." Biochem. J., 474, 1727-1739. doi: 10.1042/BCJ20170036.
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 homologues, intercalates into the kink DNA step. In this 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 (~43(o)), nearly as sharp as that produced by wild-type Cren7 (~48(o)), in the bound DNA despite the lack of side chain intercalation. L28F inserts a large hydrophobic side chain deep into the DNA step, but introduces a smaller kink (~39(o)) than that formed by the wild-type protein (~50(o)). Mutation of Leu28 into methionine yields two protein conformers differing in loop β3-β4 orientation as well as 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 β3-β4 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.

Cartoon-block schematics in six views (download the tarball)

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