Characterization of the expression and activity of the periplasmic nitrate reductase of Paracoccus pantotrophus in chemostat cultures
Characterization of the expression and activity of the periplasmic nitrate reductase of Paracoccus pantotrophus in chemostat cultures
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DOI：
10.1099/mic.0.26277-0
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发表时间：
2003-06-01
期刊：
影响因子：
2.8
通讯作者：
Ferguson, SJ
中科院分区：
文献类型：
--
作者：
Ellington, MJK;Sawers, G;Ferguson, SJ
来自泛养副球菌的周质硝酸还原酶（Nap）在细胞氧化还原平衡中起作用。先前，在P.pantotrophus中nap启动子的转录被证明对碳底物的氧化态有响应。在分批培养过程中，与更多氧化底物如琥珀酸盐相比，在还原底物如丁酸盐上生长期间表达更高。在本研究中，研究了琥珀酸盐、乙酸盐和丁酸盐限制的恒化培养物中生长速率对NAP表达的影响。在所有三种情况下，从nap启动子转录和Nap酶活性显示出很强的相关性。在对三种底物测试的最快生长速率下，当生长发生在最还原的底物（丁酸盐>乙酸盐>琥珀酸盐）上时，nap表达和Nap活性最高。然而，在所有三种情况下，观察到作为生长速率的函数的钟形表达模式，在中等生长速率下观察到最高水平的NAP表达和NAP活性。这种效果是最明显的琥珀酸，其中观察到约五倍的变化，并在中间稀释率的NAP表达和NAP活性是相当的所有三个碳基板。对从琥珀酸盐生长的培养物中制备的mRNA的分析表明，随着生长速率的变化，利用了午睡操纵子的不同转录起始位点。这项研究建立了一个新的调节功能的nap表达在泛养毕赤酵母中发生在转录水平上的生长速度在碳限制的文化。
The periplasmic nitrate reductase (Nap) from Paracoccus pantotrophus has a role in cellular redox balancing. Previously, transcription from the nap promoter in P. pantotrophus was shown to be responsive to the oxidation state of the carbon substrate. During batch culture, expression was higher during growth on reduced substrates such as butyrate compared to more oxidized substrates such as succinate. In the present study the effect of growth rate on nap expression in succinate-, acetate- and butyrate-limited chemostat cultures was investigated. In all three cases transcription from the nap promoter and Nap enzyme activity showed a strong correlation. At the fastest growth rates tested for the three substrates nap expression and Nap activity were highest when growth occurred on the most reduced substrate (butyrate > acetate > succinate). However, in all three cases a bell-shaped pattern of expression was observed as a function of growth rate, with the highest levels of nap expression and Nap activity being observed at intermediate growth rates. This effect was most pronounced on succinate, where an approximately fivefold variation was observed, and at intermediate dilution rates nap expression and Nap activity were comparable on all three carbon substrates. Analysis of mRNA prepared from the succinate-grown cultures revealed that different transcription initiation start sites for the nap operon were utilized as the growth rate changed. This study establishes a new regulatory feature of nap expression in P. pantotrophus that occurs at the level of transcription in response to growth rate in carbon-limited cultures.