Structural investigation into physiological DNA phosphorothioate modification.
Structural investigation into physiological DNA phosphorothioate modification.
复制标题
生理 DNA 硫代磷酸酯修饰的结构研究
DOI：
10.1038/srep25737
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发表时间：
2016-05-12
影响因子：
4.6
通讯作者：
Cao C
中科院分区：
文献类型：
--
作者：
Lan W;Hu Z;Shen J;Wang C;Jiang F;Liu H;Long D;Liu M;Cao C
硫代磷酸(PT)修饰是细菌的一种新的生理变异，它以序列和立体的方式取代非桥磷氧。但PT修饰对DNA性质有何影响仍不清楚。为了解决这一问题，我们制备了三个双链双链DNA解聚体d(CGPXGCCGCCGA)及其互补链d(TCGGCGPXGCCG)(其中X = O或S，即不含PT的dsDNA，[Sp，Sp]-PT dsDNA或[Rp，Rp]-PT dsDNA)位于变青链霉菌基因中。熔化温度(Tm)测量表明，[Rp，Rp]-PT dsDNA最不稳定。它们的电子转移电位测定显示其抗氧化性能的大小顺序为：SP-PTDNA >；RP-PTDNA >； 不含PT的DNA。它们的核磁共振结构表明，PT修饰不会改变它们的B型构象。[Rp，Rp]-PT dsDNA中的硫位于主槽中，在修饰位置附近对糖中的质子产生空间位阻效应，导致其不稳定，有利于其与ScoMcrA的选择性相互作用。我们认为PT的修饰对细菌是辩证的。它通过作为过氧化氢的抗氧化剂来保护宿主细菌，并作为一个标志物，指导在其他宿主中观察到的限制性内切酶，如ScoMcrA，正确地切割PT修饰的DNA，使细菌无法传播和生存。
DNA phosphorothioate (PT) modification, with sulfur replacing a nonbridging phosphate oxygen in a sequence and stereo specific manner, is a novel physiological variation in bacteria. But what effects on DNA properties PT modification has is still unclear. To address this, we prepared three double-stranded (ds) DNA decamers, d(CGPXGCCGCCGA) with its complementary strand d(TCGGCGPXGCCG) (where X = O or S,i.e., PT-free dsDNA, [Sp,Sp]-PT dsDNA or [Rp,Rp]-PT dsDNA) located in gene ofStreptomyces lividans. Their melting temperature (Tm) measurement indicates that [Rp,Rp]-PT dsDNA is most unstable. Their electron transfer potential detection presents an order of anti-oxidation properties:Sp-PT DNA >Rp-PT DNA > PT-free DNA. Their NMR structures demonstrate that PT modification doesn’t change their B-form conformation. The sulfur in [Rp,Rp]-PT dsDNA locates in the major groove, with steric effects on protons in the sugar close to modification sites, resulting in its unstability and facilitating its selectively interactions with ScoMcrA. We thought that PT modification was dialectical to the bacteria. It protects the hosting bacteria by working as antioxidant against H2O2and acts as a marker, directing restriction enzyme observed in other hosts, like ScoMcrA, to correctly cleave the PT modified DNA, so that bacteria cannot spread and survive.