ELECTRON-MICROSCOPIC STUDY OF (A)BC EXCINUCLEASE - DNA IS SHARPLY BENT IN THE UVRB DNA COMPLEX
ELECTRON-MICROSCOPIC STUDY OF (A)BC EXCINUCLEASE - DNA IS SHARPLY BENT IN THE UVRB DNA COMPLEX
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DOI：
10.1016/0022-2836(92)90957-l
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发表时间：
1992-07-20
影响因子：
5.6
通讯作者：
GRIFFITH, J
中科院分区：
文献类型：
--
作者：
SHI, Q;THRESHER, R;GRIFFITH, J
大肠杆菌中由UvrA、UvrB和UvrC蛋白启动的核苷酸切除修复UvrA是损伤识别亚基，与靶向亚基UvrB形成A2 B1复合物，该复合物与病变部位结合; UvrA解离后留下非常稳定的UvrB-DNA复合物，该复合物被触发亚基UvrC识别，随后UvrB-UvrC异二聚体形成两个切口，病变两侧各一个。利用电子显微镜，我们研究了这些早期的A，A-B中间体的DNA含有紫外光的光产物的结构。已知UvrA作为二聚体与DNA结合并产生33个碱基对的DNA酶I足迹，但它不会明显改变DNA的轨迹。A2 B1复合物清楚地显示了一种二分结构，它对DNA轨迹的影响并不总是直的或扭结的。相比之下，切割前UvrB-DNA复合物中的DNA似乎严重扭结; 43%的分子弯曲80 °或更多，平均弯曲角度为127 °。看来蛋白质诱导的弯曲是导致通过（A）BC切核酸酶切除受损核苷酸的途径上的重要步骤。
Nucleotide excision repair inEscherichia coliis initiated by the UvrA, UvrB and UvrC proteins. UvrA is the damage recognition subunit, makes an A2B1complex with the targeting subunit UvrB, and the complex binds to the lesion site; UvrA dissociates leaving behind a very stable UvrB-DNA complex that is recognized by the trigger subunit, UvrC, and the ensuing UvrB-UvrC heterodimer makes two incisions, one on either side of the lesion. Using electron microscopy, we investigated the structures of these early A, A-B intermediates on DNA containing ultraviolet light photoproducts. UvrA, which is known to bind to DNA as a dimer and produce a DNase I footprint of 33 base-pairs does not change the trajectory of DNA appreciably. The A2B1complex clearly shows a bipartite structure and its effect on the trajectory of the DNA was not consistently straight or kinked. In contrast, the DNA in the preincision UvrB-DNA complex appears to be severely kinked; 43% of the molecules are bent by 80 ° or more, with an average bending angle of 127 °. It appears that protein-induced bending is an important step on the pathway leading to excision of the damaged nucleotide by (A)BC excinuclease.