NMR Spectroscopic Elucidation of the B−Z Transition of a DNA Double Helix Induced by the Zα Domain of Human ADAR1
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- 作者：Young-Min Kang ; Jongchul Bang ; Eun-Hae Lee ; Hee-Chul Ahn ; Yeo-Jin Seo ; Kyeong Kyu Kim ; Yang-Gyun Kim ; Byong-Seok Choi ; Joon-Hwa Lee
- 刊名：Journal of the American Chemical Society
- 出版年：2009
- 出版时间：August 19, 2009
- 年：2009
- 卷：131
- 期：32
- 页码：11485-11491
- 全文大小：465K
- 年卷期：v.131,no.32(August 19, 2009)
- ISSN：1520-5126
文摘
The human RNA editing enzyme ADAR1 (double-stranded RNA deaminase I) deaminates adenine in pre-mRNA to yield inosine, which codes as guanine. ADAR1 has two left-handed Z-DNA binding domains, Zα and Zβ, at its NH2-terminus and preferentially binds Z-DNA, rather than B-DNA, with high binding affinity. The cocrystal structure of ZαADAR1 complexed to Z-DNA showed that one monomeric ZαADAR1 domain binds to one strand of double-stranded DNA and a second ZαADAR1 monomer binds to the opposite strand with 2-fold symmetry with respect to DNA helical axis. It remains unclear how ZαADAR1 protein specifically recognizes Z-DNA sequence in a sea of B-DNA to produce the stable ZαADAR1−Z-DNA complex during the B−Z transition induced by ZαADAR1. In order to characterize the molecular recognition of Z-DNA by ZαADAR1, we performed circular dichroism (CD) and NMR experiments with complexes of ZαADAR1 bound to d(CGCGCG)2 (referred to as CG6) produced at a variety of protein-to-DNA molar ratios. From this study, we identified the intermediate states of the CG6−ZαADAR1 complex and calculated their relative populations as a function of the ZαADAR1 concentration. These findings support an active B−Z transition mechanism in which the ZαADAR1 protein first binds to B-DNA and then converts it to left-handed Z-DNA, a conformation that is then stabilized by the additional binding of a second ZαADAR1 molecule.