The structure of an authentic spore photoproduct lesion in DNA suggests a basis for recognition.
The structure of an authentic spore photoproduct lesion in DNA suggests a basis for recognition.
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DOI：
10.1107/s1399004713032987
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发表时间：
2014-03
期刊：
影响因子：
--
通讯作者：
Georgiadis MM
中科院分区：
文献类型：
--
作者：
Singh I;Jian Y;Li L;Georgiadis MM
描述了双链DNA中一个孢子光生产物损伤的结构。孢子光产物损伤(SP；5-胸腺嘧啶-5，6-二氢胸腺嘧啶)是一些细菌(如枯草芽孢杆菌)经紫外线照射后的主要光产物。在孢子萌发时，这种损伤由一种特殊的修复酶--孢子光产物裂解酶(SP裂解酶)以一种不依赖于光的方式修复。本工作采用以小鼠白血病病毒逆转录酶N端片段为宿主，以脱氧核糖核酸为客体的主-客体方法，分别以2.14和1.72 的分辨率测定了含16 碱基寡核苷酸的含SP损伤和不含SP损伤的复合体的晶体结构。与其他类型的胸腺嘧啶-胸腺嘧啶损伤不同，SP损伤保留了正常的Watson-Crick氢键与互补链的腺嘌呤碱基，氢键比未损伤的DNA结构中的氢键短。然而，病变会导致B型DNA的局部构象发生结构变化。损伤周围的区域在螺旋形态上与B-DNA明显不同，与未损伤的DNA相比，小沟加宽了近3 ä。因此，这些与SP损伤相关的特殊结构特征可能为SP裂解酶的识别提供了基础。
The structure of a spore photoproduct lesion in duplex DNA is described. The spore photoproduct lesion (SP; 5-thymine-5,6-dihydrothymine) is the dominant photoproduct found in UV-irradiated spores of some bacteria such as Bacillus subtilis. Upon spore germination, this lesion is repaired in a light-independent manner by a specific repair enzyme: the spore photoproduct lyase (SP lyase). In this work, a host–guest approach in which the N-terminal fragment of Moloney murine leukemia virus reverse transcriptase (MMLV RT) serves as the host and DNA as the guest was used to determine the crystal structures of complexes including 16 bp oligonucleotides with and without the SP lesion at 2.14 and 1.72 Å resolution, respectively. In contrast to other types of thymine–thymine lesions, the SP lesion retains normal Watson–Crick hydrogen bonding to the adenine bases of the complementary strand, with shorter hydrogen bonds than found in the structure of the undamaged DNA. However, the lesion induces structural changes in the local conformation of what is otherwise B-form DNA. The region surrounding the lesion differs significantly in helical form from B-DNA, and the minor groove is widened by almost 3 Å compared with that of the undamaged DNA. Thus, these unusual structural features associated with SP lesions may provide a basis for recognition by the SP lyase.