NMR study of the Z-DNA binding mode and B-Z transition activity of the Z? domain of human ADAR1 when perturbed by mutation on the ?3 helix and ?-hairpin.
 

NMR study of the Z-DNA binding mode and B-Z transition activity of the Z? domain of human ADAR1 when perturbed by mutation on the ?3 helix and ?-hairpin.

Related Articles NMR study of the Z-DNA binding mode and B-Z transition activity of the Z? domain of human ADAR1 when perturbed by mutation on the ?3 helix and ?-hairpin.

Arch Biochem Biophys. 2014 Jul 7;

Authors: Jeong M, Lee AR, Kim HE, Choi YG, Choi BS, Lee JH

Abstract
The Z? domains of human ADAR1 (Z?ADAR1) bind to Z-DNA via interaction mediated by the ?3-core and ?-hairpin. Five residues in the ?3 helix and four residues in the ?-hairpin play important roles in Z? function, forming direct or water-mediated hydrogen bonds with DNA backbone phosphates or interacting hydrophobically with DNA bases. To understand the roles of these residues during BZ transition of duplex DNA, we performed NMR experiments on complexes of various Z?ADAR1 mutants with a 6-bp DNA duplex at various protein-to-DNA molar ratios. Our study suggests that single mutations at residues K169, N173, or Y177 cause unusual conformational changes in the hydrophobic faces of helices ?1, ?2, and ?3, which dramatically decrease the Z-DNA binding affinity. 1D imino proton spectra and chemical shift perturbation showed that single mutations at residues K170, R174, T191, P192, P193, or W195 slightly affected the Z-DNA binding affinity. A hydrogen exchange study proved that the K170A- and R174A-Z?ADAR1 proteins could efficiently change B-DNA to left-handed Z-DNA via an active BZ transition pathway, whereas the G2·C5 base pair was significantly destabilized compared to wild-type Z?ADAR1.


PMID: 25010446 [PubMed - as supplied by publisher]



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