A base-excision DNA-repair protein finds intrahelical lesion bases by fast sliding in contact with DNA
A base-excision DNA-repair protein finds intrahelical lesion bases by fast sliding in contact with DNA
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DOI：
10.1073/pnas.0509723103
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发表时间：
2006-04-11
影响因子：
11.1
通讯作者：
Xie, XS
中科院分区：
文献类型：
--
作者：
Blainey, PC;van Oijent, AM;Xie, XS
位点特异性DNA结合蛋白功能的一个中心谜团是快速定位和结合DNA中目标位点的详细机制。例如，人类氧鸟嘌呤DNA糖基酶1(HOgg1)必须寻找罕见的8-氧鸟嘌呤损伤，以防止氧化应激引起的颠倒突变。在这里，我们报告了单个hOgg1酶分子沿剪切流拉伸的DNA扩散的高速成像。依赖于盐浓度的测量表明，这种扩散发生在hOgg1与DNA持续接触的情况下。在接近生理的pH和盐浓度下，hOgg1与DNA的结合时间为亚秒，其扩散常数高达5×10(6)BP(2)/S，接近一维扩散的理论上限，表明滑动的活化势垒仅为0.5kcal/mol(1kcal=4.2W)。这种几乎无障碍的布朗滑动表明，DNA糖基酶通过大量冗余的搜索来定位损伤碱基，在这种搜索中，酶在动力学控制下选择性地结合8-氧鸟嘌呤。
A central mystery in the function of site-specific DNA-binding proteins is the detailed mechanism for rapid location and binding of target sites in DNA. Human oxoguanine DNA glycosylase 1 (hOgg1), for example, must search out rare 8-oxoguanine lesions to prevent transversion mutations arising from oxidative stress. Here we report high-speed imaging of single hOgg1 enzyme molecules diffusing along DNA stretched by shear flow. Salt-concentration-dependent measurements reveal that such diffusion occurs as hOgg1 slides in persistent contact with DNA. At near-physiologic pH and salt concentration, hOgg1 has a subsecond DNA-binding time and slides with a diffusion constant as high as 5 x 10(6) bp(2)/S. Such a value approaches the theoretical upper limit for one-dimensional diffusion and indicates an activation barrier for sliding of only 0.5 kcal/mol (1 kcal = 4.2 W). This nearly barrierless Brownian sliding indicates that DNA glycosylases locate lesion bases by a massively redundant search in which the enzyme selectively binds 8-oxoguanine under kinetic control.