Transcriptional regulation in response to oxygen and nitrate of the operons encoding the [NiFe] hydrogenases 1 and 2 of Escherichia coli
Transcriptional regulation in response to oxygen and nitrate of the operons encoding the [NiFe] hydrogenases 1 and 2 of Escherichia coli
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DOI：
10.1099/00221287-145-10-2903
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发表时间：
1999-10-01
期刊：
影响因子：
2.8
通讯作者：
Boxer, DH
中科院分区：
文献类型：
--
作者：
Richard, DJ;Sawers, G;Boxer, DH
合成的[NiFe]氢化酶1和2的大肠杆菌是诱导响应厌氧和抑制时，硝酸盐存在于生长培养基中。氢化酶1和氢化酶2分别由多顺反子hyaABCDEF和hybOABCDEFG操纵子编码。引物延伸分析用于确定两个操纵子的转录起始位点。这允许构建单拷贝lacZ操纵子融合体，其用于检查两个操纵子的转录调控。两者的表达均由厌氧诱导，并被硝酸盐抑制，这与早期的生化研究完全雅阁。hyb操纵子的厌氧诱导仅部分依赖于FNR蛋白，并且令人惊讶的是，通过arcA突变增强。后者的结果表明，ArcA抑制厌氧hyb表达，并进一步的因素，这仍有待确定，参与控制操纵子表达的厌氧诱导。硝酸盐对hyb表达的抑制是由NarL/NarX和NarP/NarQ双组分调控系统介导的。值得注意的是，一个narP突变缺乏厌氧诱导hyb表达，即使在没有添加硝酸盐。厌氧诱导hya表达依赖于ArcA和AppY调节剂，这证实了其他作者的早期观察结果。硝酸盐阻遏的透明质酸操纵子介导的NarL和NarP。总之，这些数据表明，虽然hya和hyb操纵子共享共同的监管机构，有重要的差异，在控制表达的个别操纵子。
Synthesis of the [NiFe] hydrogenases 1 and 2 of Escherichia coli is induced in response to anaerobiosis and is repressed when nitrate is present in the growth medium. The hydrogenase 1 and hydrogenase 2 enzymes are encoded by the polycistronic hyaABCDEF and hybOABCDEFG operons, respectively. Primer extension analysis was used to determine the initiation site of transcription of both operons. This permitted the construction of single-copy lacZ operon fusions, which were used to examine the transcriptional regulation of the two operons. Expression of both was induced by anaerobiosis and repressed by nitrate, which is in complete accord with earlier biochemical studies. Anaerobic induction of the hyb operon was only partially dependent on the FNR protein and, surprisingly, was enhanced by an arcA mutation. This latter result indicated that ArcA suppresses anaerobic hyb expression and that a further factor, which remains to be identified, is involved in controlling anaerobic induction of operon expression. Nitrate repression of hyb expression was mediated by the NarL/NarX and NarP/NarQ two-component regulatory systems. Remarkably, a narP mutant lacked anaerobic induction of hyb expression, even in the absence of added nitrate. Anaerobic induction of hya expression was dependent on the ArcA and AppY regulators, which confirms earlier observations by other authors. Nitrate repression of the hya operon was mediated by both NarL and NarP. Taken together, these data indicate that although the hya and hyb operons share common regulators, there are important differences in the control of expression of the individual operons.