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ATP、ADP和P1 ParB对P1质粒分配蛋白ParA的调节作用。

Modulation of the P1 plasmid partition protein ParA by ATP, ADP, and P1 ParB.

作者信息

Davey M J, Funnell B E

机构信息

Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada.

出版信息

J Biol Chem. 1997 Jun 13;272(24):15286-92. doi: 10.1074/jbc.272.24.15286.

Abstract

ParA is an essential P1 plasmid partition protein. It represses transcription of the par genes (parA and parB) and is also required for a second, as yet undefined step in partition. ParA is a ParB-stimulated ATPase that binds to a specific DNA site in the par promoter region. ATP binding and hydrolysis by ParA affect ParA activities in vitro. ATP and ADP binding stimulate ParA DNA binding and dimerization; however, ATP hydrolysis has a negative effect on DNA binding. Our current experiments reveal that ATP binding and hydrolysis affect ParA conformation and ParA sensitivity to ParB. Nucleotide binding assays show that ParA binds ATP better than ADP (Kd values of 33 and 50 microM, respectively). Interaction with these nucleotides as well as ATP hydrolysis by ParA alter ParA conformation as established by CD and ParA sensitivity to heat denaturation. Finally, we show that ParB stimulates ParA DNA binding. This stimulation requires ATP hydrolysis in vitro, suggesting that one role for ATP hydrolysis in vivo is to make ParA repressor sensitive to ParB. Our observations lead to the suggestion that ATP binding and hydrolysis have separable roles in ParA repressor function and perhaps in ParA partition functions as well.

摘要

ParA是一种必需的P1质粒分配蛋白。它抑制par基因(parA和parB)的转录,并且在分配过程的第二步(尚未明确)中也是必需的。ParA是一种受ParB刺激的ATP酶,它与par启动子区域的一个特定DNA位点结合。ParA的ATP结合和水解会影响其体外活性。ATP和ADP结合会刺激ParA与DNA结合以及二聚化;然而,ATP水解对DNA结合有负面影响。我们目前的实验表明,ATP结合和水解会影响ParA的构象以及ParA对ParB的敏感性。核苷酸结合分析表明,ParA与ATP的结合能力优于ADP(Kd值分别为33和50微摩尔)。与这些核苷酸的相互作用以及ParA的ATP水解会改变ParA的构象,这是通过圆二色光谱(CD)和ParA对热变性的敏感性确定的。最后,我们表明ParB会刺激ParA与DNA结合。这种刺激在体外需要ATP水解,这表明ATP水解在体内的一个作用是使ParA阻遏蛋白对ParB敏感。我们的观察结果表明,ATP结合和水解在ParA阻遏蛋白功能中可能具有可分离的作用,也许在ParA分配功能中也是如此。

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