PROTEIN-KINASE AND PHOSPHOPROTEIN PHOSPHATASE-ACTIVITIES OF NITROGEN REGULATORY PROTEINS NTRB AND NTRC OF ENTERIC BACTERIA - ROLES OF THE CONSERVED AMINO-TERMINAL DOMAIN OF NTRC
PROTEIN-KINASE AND PHOSPHOPROTEIN PHOSPHATASE-ACTIVITIES OF NITROGEN REGULATORY PROTEINS NTRB AND NTRC OF ENTERIC BACTERIA - ROLES OF THE CONSERVED AMINO-TERMINAL DOMAIN OF NTRC
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DOI：
10.1073/pnas.85.14.4976
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发表时间：
1988-07-01
影响因子：
11.1
通讯作者：
KUSTU, S
中科院分区：
文献类型：
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作者：
KEENER, J;KUSTU, S
肠细菌的NTRC蛋白（ntrC产物）通过含有ntrA产物（σ 54）作为σ的RNA聚合酶的全酶形式激活氮调节基因的转录。因子虽然未修饰的NTRC会与DNA结合，但它必须被磷酸化以激活转录。NTRC的磷酸化和去磷酸化都在NTRB蛋白（ntrB产物）存在下发生。我们在这里严格证明，这是NTRB蛋白是一种蛋白激酶，通过显示NTRB可以磷酸化本身，而NTRC不能。磷酸化的NTRC（NTRC-P）能够在37 ℃下以0.14-0.19 min-1（t1/2为5.0-3.6 min）的一级速率常数自动去磷酸化。C.此外，有调节去磷酸化的NTRC-P。通过自磷酸化酶的活性相比，调节去磷酸化需要三个组件，除了NTRC-P：PII调节蛋白，NTRB，和ATP。NTRC在其氨基末端结构域内被磷酸化，该结构域在多种真细菌中的许多双组分调节系统的一个伴侣中是保守的。将纯化的NTRC的氨基末端片段（12.5 kDa）足以被NTRB识别，并且以与天然蛋白相同的速率自动去磷酸化。
The NTRC protein (ntrC product) of enteric bacteria activates transcription of nitrogen-regulated genes by a holoenzyme form of RNA polymerase that contains the ntrA product (.sigma.54) as .sigma. factor. Although unmodified NTRC will bind to DNA, it must be phosphorylated to activate transcription. Both phosphorylation and dephosphorylation of NTRC occur in the presence of the NTRB protein (ntrB product). We here demonstrate rigorously that it is the NTRB protein that is a protein kinase by showing that NTRB can phosphorylate itself, whereas NTRC cannot. Phosphorylated NTRC (NTRC-P) is capable of autodephosphorylation with a first-order rate constant of 0.14-0.19 min-1 (t1/2 of 5.0-3.6 min) at 37.degree. C. In addition, there is regulated dephosphorylation of NTRC-P. By contrast to the autophosphatase activity, regulated dephosphorylation requires three components in addition to NTRC-P: the PII regulatory protein, NTRB, and ATP. NTRC is phosphorylated within its amino-terminal domain, which is conserved in one partner of a number of two-component regulatory systems in a wide variety of eubacteria. A purified amino-terminal fragment of NTRC (.apprxeq. 12.5 kDa) is sufficient for recognition by NTRB and is autodephosphorylated at the same rate as the native protein.