The F-plasmid TraI protein contains three functional domains required for conjugative DNA strand transfer.
The F-plasmid TraI protein contains three functional domains required for conjugative DNA strand transfer.
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F-质粒 TraI 蛋白包含接合 DNA 链转移所需的三个功能域。
DOI：
10.1128/jb.187.2.697-706.2005
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Ragonese,Heather
中科院分区：
文献类型：
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作者：
Matson,StevenW;Ragonese,Heather
f质粒编码的TraI蛋白，也被称为DNA解旋酶I，是一种共轭DNA转移所需的双功能蛋白。该酶催化与偶联相关的DNA加工事件所需的两个不同但功能相关的反应：提供启动链转移所需的缺口的位点和链特异性酯交换（松弛酶）反应和提供链转移动力的5 ‘到3 ’解旋酶反应。先前的研究已经确定了松弛结构域，它包含蛋白质的第一个~ 310个氨基酸。解旋酶相关基序位于氨基酸990和1450之间。氨基酸310和990之间的区域以及氨基酸1450到c端之间的区域的功能未知。构建了一种缺乏c端252个氨基酸的蛋白质（TraIΔ252），并显示其基本上具有野生型的转酯酶和解旋酶活性。此外，该蛋白能够与最小松弛体的其他组分进行功能性相互作用。然而，TraIΔ252在遗传互补实验中不能支持共轭DNA转移。我们得出结论，TraIΔ252缺乏DNA转移所需的基本c端结构域。我们推测这个结构域可能与DNA转移机制的其他组成部分的基本蛋白质-蛋白质相互作用有关。
The F-plasmid-encoded TraI protein, also known as DNA helicase I, is a bifunctional protein required for conjugative DNA transfer. The enzyme catalyzes two distinct but functionally related reactions required for the DNA processing events associated with conjugation: the site- and strand-specific transesterification (relaxase) reaction that provides the nick required to initiate strand transfer and a processive 5′-to-3′ helicase reaction that provides the motive force for strand transfer. Previous studies have identified the relaxase domain, which encompasses the first ∼310 amino acids of the protein. The helicase-associated motifs lie between amino acids 990 and 1450. The function of the region between amino acids 310 and 990 and the region from amino acid 1450 to the C-terminal end is unknown. A protein lacking the C-terminal 252 amino acids (TraIΔ252) was constructed and shown to have essentially wild-type levels of transesterase and helicase activity. In addition, the protein was capable of a functional interaction with other components of the minimal relaxosome. However, TraIΔ252 was not able to support conjugative DNA transfer in genetic complementation experiments. We conclude that TraIΔ252 lacks an essential C-terminal domain that is required for DNA transfer. We speculate this domain may be involved in essential protein-protein interactions with other components of the DNA transfer machinery.