The nuclease A inhibitor represents a new variation of the rare PR-1 fold
The nuclease A inhibitor represents a new variation of the rare PR-1 fold
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DOI：
10.1016/s0022-2836(02)00460-6
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发表时间：
2002-07-19
影响因子：
5.6
通讯作者：
London, RE
中科院分区：
文献类型：
--
作者：
Kirby, TW;Mueller, GA;London, RE
核酸酶A （NucA）是一种非特异性核酸内切酶，能够降解单链和双链DNA和RNA。核酸酶A抑制剂（NuiA）以1:1的化学计量和皮摩尔亲和力与NucA结合，抑制了核内溶活性。为了更好地了解NuiA的抑制机理，采用NMR方法测定了NuiA的溶液结构。NuiA的折叠是一个α - β - α三明治，但DALI和TOP的标准数据库搜索显示没有结构同源性。CATH数据库中α - β - α折叠的目视检查显示与pr -1样折叠（SCOP命名法）相似。相似之处包括二级结构元素的排序,脸上有一个螺旋的alpha-beta-alpha三明治,和三螺旋的脸。然而，一个主要的区别是在IV螺旋上，它在PR-1折叠中很短，垂直于I和III螺旋，而在NuiA折叠中很长，平行于I和III螺旋。此外，在β -sheet中插入一条链使得NuiA β -sheet在组织上完全反平行。NuiA的快速时标运动，其特征是螺旋III和螺旋IV之间扩展环的柔韧性增强，也与P14a相似，后者是PR-1折叠。我们提出，PR-1折叠的目的是形成一个稳定的支架，以呈现这种扩展结构与其他蛋白质的生物相互作用。这一假设得到了数据的支持，这些数据表明，当NuiA与NucA结合时，在螺旋III和IV之间的扩展环中发生了显著的化学位移变化。(C) 2002 Elsevier Science Ltd.。版权所有。
Nuclease A (NucA) from Anabaena sp. is a non-specific endonuclease able to degrade single and double-stranded DNA and RNA. The endonucleolytic activity is inhibited by the nuclease A inhibitor (NuiA), which binds to NucA with 1:1 stoichiometry and picomolar affinity. In order to better understand the mechanism of inhibition, the solution structure of NuiA was determined by NMR methods. The fold of NuiA is an alpha-beta-alpha sandwich but standard database searches by DALI and TOP revealed no structural homologies. A visual inspection of alpha-beta-alpha folds in the CATH database revealed similarities to the PR-1-like fold (SCOP nomenclature). The similarities include the ordering of secondary structural elements, a single helix on one face of the alpha-beta-alpha sandwich, and three helices on the other face. However, a major difference is in the IV helix, which in the PR-1 fold is short and perpendicular to the I and III helices, but in NuiA is long and parallel to the I and III helices. Additionally, a strand insertion in the beta-sheet makes the NuiA beta-sheet completely antiparallel in organization. The fast time-scale motions of NuiA, characterized by enhanced flexibility of the extended loop between helices III and IV, also show similarities to P14a, which is a PR-1 fold. We propose that the purpose of the PR-1 fold is to form a stable scaffold to present this extended structure for biological interactions with other proteins. This hypothesis is supported by data that show that when NuiA is bound to NucA significant changes in chemical shift occur in the extended loop between helices III and IV. (C) 2002 Elsevier Science Ltd. All rights reserved.