Structural characterization of the redefined DNA-binding domain of human XPA
Structural characterization of the redefined DNA-binding domain of human XPA
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重新定义的人类 XPA DNA 结合域的结构表征
DOI：
10.1016/j.bbrc.2019.05.050
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发表时间：
2019
影响因子：
3.1
通讯作者：
Qian Chengmin
中科院分区：
文献类型：
--
作者：
Lian Fu-Ming;Yang Xiangwei;Yang Wancai;Jiang Yong-Liang;Qian Chengmin
着色性干皮病互补组蛋白（xeroderma pigmentosum complementation group A，XPA）是核苷酸切除修复（nucleotide execution repair，NER）途径中的一个关键支架蛋白，在DNA损伤的确认和修复蛋白的募集中起着重要作用。早期的研究已经将XPA的最小DNA结合结构域（MBD）映射到对应于残基98-219的区域。然而，最近的研究表明，涉及残基98-239的区域是重新定义的DNA结合结构域（DBD），其以比MBD高得多的结合亲和力结合DNA底物，并且对全长XPA蛋白具有几乎相同的结合亲和力。然而，XPA的重新定义的DBD结构域（XPA-DBD）的结构仍有待研究。在这里，我们提出了XPA-DBD的晶体结构在2.06纳米分辨率。与先前报道的MBD结构相比，XPA的C-末端区域的结构已经延长了21个残基（Arg 211-Arg 231）。其结构显示C-末端延伸（Arg 211-Arg 231）折叠为具有多个碱性残基的α-螺旋。在最后一个C-末端螺旋中形成的带正电荷的表面表明其在DNA结合中的关键作用。进一步的结构分析表明，XPA-DBD的最后一个C-末端区域（Asp 217-Thr 239）可能发生构象变化，以直接结合DNA底物。本研究为深入了解XPA-DBD增强DNA结合力的可能机制提供了结构基础。
XPA (xeroderma pigmentosum complementation group A), a key scaffold protein in nucleotide excision repair (NER) pathway, is important in DNA damage verification and repair proteins recruitment. Earlier studies had mapped the minimal DNA-binding domain (MBD) of XPA to a region corresponding to residues 98–219. However, recent studies indicated that the region involving residues 98–239 is the redefined DNA-binding domain (DBD), which binds to DNA substrates with a much higher binding affinity than MBD and possesses a nearly identical binding affinity to the full-length XPA protein. However, the structure of the redefined DBD domain of XPA (XPA-DBD) remains to be investigated. Here, we present the crystal structure of XPA-DBD at 2.06 Å resolution. Structure of the C-terminal region of XPA has been extended by 21 residues (Arg211–Arg231) as compared with previously reported MBD structures. The structure reveals that the C-terminal extension (Arg211–Arg231) is folded as an α-helix with multiple basic residues. The positively charged surface formed in the last C-terminal helix suggests its critical role in DNA binding. Further structural analysis demonstrates that the last C-terminal region (Asp217–Thr239) of XPA-DBD might undergo a conformational change to directly bind to the DNA substrates. This study provides a structural basis for understanding the possible mechanism of enhanced DNA-binding affinity of XPA-DBD.