INTERMOLECULAR COMPLEMENTATION BETWEEN 2 DEFECTIVE MUTANT SIGNAL-TRANSDUCING RECEPTORS OF ESCHERICHIA-COLI
INTERMOLECULAR COMPLEMENTATION BETWEEN 2 DEFECTIVE MUTANT SIGNAL-TRANSDUCING RECEPTORS OF ESCHERICHIA-COLI
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DOI：
10.1073/pnas.88.24.11057
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发表时间：
1991-12-01
影响因子：
11.1
通讯作者：
INOUYE, M
中科院分区：
文献类型：
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作者：
YANG, Y;INOUYE, M
Taz 1是天冬氨酸化学受体Tar和大肠杆菌的Escherichia coli Esch当Taz 1 His-277（细胞质EnvZ结构域中的自磷酸化位点）被缬氨酸残基取代时，突变体Taz 1无法诱导ompC表达。类似地，当大约三分之二的EnvZ结构域被删除时，Taz 1是无功能的。然而，当这两个有缺陷的Taz 1蛋白在细胞中共表达时，ompC组成型表达。与此结果一致，两个突变Taz 1分子能够在体外分子间互补以恢复OmpR激酶活性，但不能恢复磷酸酶活性。用EnvZ也获得了相同的结果。目前的结果表明，Taz 1和EnvZ的自磷酸化是一个分子间的磷酸化反应，需要形成一个二聚体（或寡聚体），和配体依赖性ompC的表达不仅需要激酶，但也磷酸酶活性。
Taz1 is a hybrid signal-transducing membrane receptor between Tar, an aspartate chemoreceptor, and EnvZ, an osmosensor of Escherichia coli that is able to induce ompC expression by phosphorylating OmpR (a transcriptional activator) in response to aspartate. When the Taz1 His-277, the proposed autophosphorylation site in the cytoplasmic EnvZ domain, was replaced with a valine residue, the mutant Taz1 was unable to induce ompC expression. Similarly, when approximately two-thirds of the EnvZ domain was deleted, Taz1 was nonfunctional. However, when these two defective Taz1 proteins were coexpressed in a cell, ompC was constitutively expressed. Coinciding with this result, two mutant Taz1 molecules were able to intermolecularly complement each other to restore the OmpR kinase activity but not phosphatase activity in vitro. The identical result was also obtained with EnvZ. The present results suggest that the autophosphorylation of Taz1 and EnvZ is an intermolecular phosphorylation reaction, requiring formation of a dimer (or oligomer), and that ligand-dependent ompC expression requires not only kinase but also phosphatase activity.