ParG, a protein required for active partition of bacterial plasmids, has a dimeric ribbon-helix-helix structure
ParG, a protein required for active partition of bacterial plasmids, has a dimeric ribbon-helix-helix structure
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DOI：
10.1046/j.1365-2958.2003.03750.x
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发表时间：
2003-11-01
影响因子：
3.6
通讯作者：
Lian, LY
中科院分区：
文献类型：
--
作者：
Golovanov, AP;Barillà, D;Lian, LY
ParG蛋白（8.6 kDa）是多药耐药质粒TP228 DNA分割复合物的重要组成部分。在溶液中，ParG是一种二聚体，与parFG基因上游的DNA序列相互作用，在靶DNA缺失和存在的情况下也与ParF分割蛋白相互作用。本文报道了ParG溶液的核磁共振结构。ParG二聚体由两个紧密缠绕的c端部分（33-76）组成的折叠结构域和两个由n端区域（1-32）组成的高流动性尾部组成。ParG折叠部分具有与dna结合转录抑制因子Arc/MetJ超家族相似的带状-螺旋-螺旋（RHH）结构，尽管初级序列相似性非常低。ParG主要通过其折叠结构域与DNA相互作用；这种相互作用与聚g寡聚结合在一起。ParG的二聚体RHH结构表明，ParG通过在DNA的主要凹槽中插入双链β片与DNA结合，其方式类似于来自Arc/MetJ超家族的转录抑制因子，并且ParG本身可以作为转录抑制因子发挥作用。提出了一种新的蛋白质分类方法，属于Arc/MetJ超家族和ParG同源物，基于一个保守的带正电的残基在DNA识别基序的一部分-链的开始或结束的位置。
The ParG protein (8.6 kDa) is an essential component of the DNA partition complex of multidrug resistance plasmid TP228. ParG is a dimer in solution, interacts with DNA sequences upstream of the parFG genes and also with the ParF partition protein both in the absence and presence of target DNA. Here, the solution nuclear magnetic resonance structure of ParG is reported. The ParG dimer is composed of a folded domain formed by two closely intertwined C-terminal parts (residues 33-76), and two highly mobile tails consisting of N-terminal regions (residues 1-32). The folded part of ParG has the ribbon-helix-helix (RHH) architecture similar to that of the Arc/MetJ superfamily of DNA-binding transcriptional repressors, although the primary sequence similarity is very low. ParG interacts with DNA predominantly via its folded domain; this interaction is coupled with ParG oligomerization. The dimeric RHH structure of ParG suggests that it binds to DNA by inserting the double-stranded beta-sheet into the major groove of DNA, in a manner similar to transcriptional repressors from the Arc/MetJ superfamily, and that ParG can function as a transcriptional repressor itself. A new classification of proteins belonging to the Arc/MetJ superfamily and ParG homologues is proposed, based on the location of a conserved positively charged residue at either the beginning or at the end of the beta-strand which forms part of the DNA recognition motif.