Structural Model for Deoxycytidine Deamination Mechanisms of the HIV-1 Inactivation Enzyme APOBEC3G
Structural Model for Deoxycytidine Deamination Mechanisms of the HIV-1 Inactivation Enzyme APOBEC3G
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DOI：
10.1074/jbc.m110.107987
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发表时间：
2010-05-21
影响因子：
4.8
通讯作者：
Goodman, Myron F.
中科院分区：
文献类型：
--
作者：
Chelico, Linda;Prochnow, Courtney;Goodman, Myron F.
APOBEC 3G（Apo 3G）是一种单链DNA依赖性脱氧胞苷脱氨酶，在不存在人类免疫缺陷病毒（HIV）病毒感染因子的情况下，其被包裹在HIV病毒粒子中。随后，Apo 3G通过在新生负链cDNA上以3 '-> 5'极性的C -> U进行前脱氨来触发病毒失活。Apo 3G具有无催化活性的N-末端CD 1结构域和活性的C-末端CD 2结构域。Apo 3G以单体、二聚体、四聚体和高阶寡聚体的形式存在，其分布取决于DNA底物和盐。在这里，我们使用多角度光散射和原子力显微镜，以确定低聚状态的Apo 3G。设计用于破坏预测的CD 1-CD 1二聚体界面处的二聚化的双突变体（F126 A/W127 A）主要将Apo 3G转化为结合单链DNA的单体，Alu RNA，并催化具有3 '-> 5'脱氨基极性的进行性C -> U脱氨基，类似于天然Apo 3G。CD 1结构域对于持续合成能力和极性都是必不可少的。我们提出了一个基于结构的模型来解释Apo 3G的扫描和催化行为。
APOBEC3G (Apo3G) is a single-stranded DNA-dependent deoxycytidine deaminase, which, in the absence of the human immunodeficiency virus (HIV) viral infectivity factor, is encapsulated into HIV virions. Subsequently, Apo3G triggers viral inactivation by processively deaminating C -> U, with 3'-> 5' polarity, on nascent minus-strand cDNA. Apo3G has a catalytically inactive N-terminal CD1 domain and an active C-terminal CD2 domain. Apo3G exists as monomers, dimers, tetramers, and higher order oligomers whose distributions depend on DNA substrate and salt. Here we use multiangle light scattering and atomic force microscopy to identify oligomerization states of Apo3G. A double mutant (F126A/W127A), designed to disrupt dimerization at the predicted CD1-CD1 dimer interface, predominantly converts Apo3G to a monomer that binds single-stranded DNA, Alu RNA, and catalyzes processive C -> U deaminations with 3'-> 5' deamination polarity, similar to native Apo3G. The CD1 domain is essential for both processivity and polarity. We propose a structure-based model to explain the scanning and catalytic behavior of Apo3G.