Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Stafford Hall, 95 Carrigan Drive, Burlington, VT 05405-0068, USA.
Structure. 2013 Feb 5;21(2):247-56. doi: 10.1016/j.str.2012.12.008. Epub 2013 Jan 9.
Endonuclease VIII-like 3 (Neil3) is a DNA glycosylase of the base excision repair pathway that protects cells from oxidative DNA damage by excising a broad spectrum of cytotoxic and mutagenic base lesions. Interestingly, Neil3 exhibits an unusual preference for DNA with single-stranded regions. Here, we report the 2.0 Å crystal structure of a Neil3 enzyme. Although the glycosylase region of mouse Neil3 (MmuNeil3Δ324) exhibits the same overall fold as that of other Fpg/Nei proteins, it presents distinct structural features. First, MmuNeil3Δ324 lacks the αF-β9/10 loop that caps the flipped-out 8-oxoG in bacterial Fpg, which is consistent with its inability to cleave 8-oxoguanine. Second, Neil3 not only lacks two of the three void-filling residues that stabilize the opposite strand, but it also harbors negatively charged residues that create an unfavorable electrostatic environment for the phosphate backbone of that strand. These structural features provide insight into the substrate specificity and marked preference of Neil3 for ssDNA.
内切核酸酶 VIII 样蛋白 3（Neil3）是碱基切除修复途径中的一种 DNA 糖苷酶，可通过切除广泛的细胞毒性和致突变碱基损伤来保护细胞免受氧化 DNA 损伤。有趣的是，Neil3 对具有单链区域的 DNA 表现出异常的偏好。在这里，我们报告了 Neil3 酶的 2.0Å 晶体结构。尽管小鼠 Neil3（MmuNeil3Δ324）的糖苷酶区域与其他 Fpg/Nei 蛋白具有相同的整体折叠，但它呈现出独特的结构特征。首先，MmuNeil3Δ324 缺乏覆盖细菌 Fpg 中翻转的 8-氧鸟嘌呤的αF-β9/10 环，这与其不能切割 8-氧鸟嘌呤一致。其次，Neil3 不仅缺乏稳定相反链的三个空洞填充残基中的两个，而且还含有带负电荷的残基，为该链的磷酸骨架创造了不利的静电环境。这些结构特征提供了对 Neil3 对 ssDNA 的底物特异性和明显偏好的深入了解。
