Crystal Structure of DNA Cytidine Deaminase ABOBEC3G Catalytic Deamination Domain Suggests a Binding Mode of Full-length Enzyme to Single-stranded DNA
Crystal Structure of DNA Cytidine Deaminase ABOBEC3G Catalytic Deamination Domain Suggests a Binding Mode of Full-length Enzyme to Single-stranded DNA
复制标题
DNA胞苷脱氨酶ABOBEC3G催化脱氨结构域的晶体结构表明全长酶与单链DNA的结合模式
DOI：
10.1074/jbc.m114.624262
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发表时间：
2015-02-13
影响因子：
4.8
通讯作者：
Cao, Chunyang
中科院分区：
文献类型：
--
作者：
Lu, Xiuxiu;Zhang, Tianlong;Cao, Chunyang
APOBEC 3G（A3 G）是一种DNA胞苷脱氨酶（CD），对人类免疫缺陷病毒1（HIV-1）和其他病原性病毒具有抗病毒活性。它有一个无活性的N-末端CD 1病毒感染因子（Vif）蛋白结合结构域（A3 G-CD 1）和一个活性催化的C-末端CD 2脱氨结构域（A3 G-CD 2）。虽然A3 G-CD 2的结构和全长A3 G的酶学性质已经有了很多研究报道，但A3 G如何与HIV-1单链DNA（ssDNA）相互作用的机制仍然没有得到很好的表征。在这里，我们报道了一种新的A3 G-CD 2头-尾二聚体的晶体结构（其中单体H（头部）的N末端与单体T（尾部）的C末端相互作用），其中观察到连续的DNA结合沟。通过构建A3 G-CD 1的结构模型，我们发现它的整体折叠几乎与A3 G-CD 2相同。我们突变了位于单体H中的沟中或沿着沟的残基和A3 G-CD 1中对应于位于单体T中的沟中或沿着沟的残基。然后，通过进行酶促测定，我们证实了报道的关键元件和A3 G中催化脱氨所必需的残基。此外，我们还鉴定了A3 G中10多个与DNA结合和脱氨反应有关的残基。因此，这种二聚体结构可能代表全长A3 G的结构模型，这表明A3 G与HIV-1 ssDNA的可能结合模式。
APOBEC3G (A3G) is a DNA cytidine deaminase (CD) that demonstrates antiviral activity against human immunodeficiency virus 1 (HIV-1) and other pathogenic virus. It has an inactive N-terminal CD1 virus infectivity factor (Vif) protein binding domain (A3G-CD1) and an actively catalytic C-terminal CD2 deamination domain (A3G-CD2). Although many studies on the structure of A3G-CD2 and enzymatic properties of full-length A3G have been reported, the mechanism of how A3G interacts with HIV-1 single-stranded DNA (ssDNA) is still not well characterized. Here, we reported a crystal structure of a novel A3G-CD2 head-to-tail dimer (in which the N terminus of the monomer H (head) interacts with the C terminus of monomer T (tail)), where a continuous DNA binding groove was observed. By constructing the A3G-CD1 structural model, we found that its overall fold was almost identical to that of A3G-CD2. We mutated the residues located in or along the groove in monomer H and the residues in A3G-CD1 that correspond to those seated in or along the groove in monomer T. Then, by performing enzymatic assays, we confirmed the reported key elements and the residues in A3G necessary to the catalytic deamination. Moreover, we identified more than 10 residues in A3G essential to DNA binding and deamination reaction. Therefore, this dimer structure may represent a structural model of full-length A3G, which indicates a possible binding mode of A3G to HIV-1 ssDNA.