NMR Spectroscopic Elucidation of the B-Z Transition of a DNA Double Helix Induced by the Zα Domain of Human ADAR1
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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DOI：
10.1021/ja902654u
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发表时间：
2009-08-19
影响因子：
15
通讯作者：
Lee, Joon-Hwa
中科院分区：
文献类型：
--
作者：
Kang, Young-Min;Bang, Jongchul;Lee, Joon-Hwa
人类RNA编辑酶ADAR1(双链RNA脱氨酶1)将前信使核糖核酸中的腺嘌呤脱氨基，生成肌苷，其编码为鸟嘌呤。ADAR1在其NH2末端有两个左旋Z-DNA结合域，Zα和Zβ，并且优先结合Z-DNA，而不是B-DNA，具有高结合亲和力。Z(αADAR1)与Z-DNA络合的共晶结构表明，一个单体Z(αADAR1)结构域结合到双链DNA的一条链上，第二个Z(αADAR1)单体以相对于DNA螺旋轴的2倍对称性结合到相反的链上。目前尚不清楚Z(αADAR1)蛋白如何在由Z(αADAR1)诱导的B-Z转变过程中特异性识别B-DNA海洋中的Z-DNA序列，从而产生稳定的Z(αADAR1)-Z-DNA复合体。为了表征Z(α-ADAR1)对Z-DNA的分子识别作用，我们对不同蛋白质与DNA摩尔比的Z(α-ADAR1)与d(CGCGCG)(2)的络合物(简称CG6)进行了圆二色谱(CD)和核磁共振实验。从这项研究中，我们确定了CG6-Z(αADAR1)络合物的中间态，并计算了它们的相对布居数作为Z(αADAR1)浓度的函数。这些发现支持一种活性的B-Z转换机制，在该机制中，Z(αADAR1)蛋白首先与B-DNA结合，然后将其转换为左手Z-DNA，然后通过第二个Z(αADAR1)分子的额外结合来稳定这一构象。
The human RNA editing enzyme ADAR1 (double-stranded RNA deaminase 1) deaminates adenine in pre-mRNA to yield inosine, which codes as guanine. ADAR1 has two left-handed Z-DNA binding domains, Z alpha and Z beta, at its NH2-terminus and preferentially binds Z-DNA, rather than B-DNA, with high binding affinity. The cocrystal structure Of Z(alpha ADAR1) complexed to Z-DNA showed that one monomeric Z(alpha ADAR1) domain binds to one strand of double-stranded DNA and a second Z(alpha ADAR1) monomer binds to the opposite strand with 2-fold symmetry with respect to DNA helical axis. It remains unclear how Z(alpha ADAR1) protein specifically recognizes Z-DNA sequence in a sea of B-DNA to produce the stable Z(alpha ADAR1)-Z-DNA complex during the B-Z transition induced by Z(alpha ADAR1). In order to characterize the molecular recognition of Z-DNA by Z(alpha ADAR1), we performed circular dichroism (CD) and NMR experiments with complexes Of Z(alpha ADAR1) 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-Z(alpha ADAR1) complex and calculated their relative populations as a function of the Z(alpha ADAR1) concentration. These findings support an active B-Z transition mechanism in which the Z(alpha ADAR1) 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 Z(alpha ADAR1) molecule.