Aerobic regulation of the Escherichia coli tonB gene by changes in iron availability and the fur locus.
Aerobic regulation of the Escherichia coli tonB gene by changes in iron availability and the fur locus.
复制标题
通过铁可用性和毛皮基因座的变化对大肠杆菌 tonB 基因进行有氧调节。
DOI：
10.1128/jb.172.5.2287-2293.1990
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发表时间：
1990
影响因子：
3.2
通讯作者：
Postle,K
中科院分区：
文献类型：
--
作者：
Postle,K
tonB基因是几种不同的铁-铁载体复合物跨大肠杆菌外膜运输所必需的。在这项研究中，tonB基因的转录调控进行了研究，通过使用三种不同的tonB-lacZ融合监测tonB的表达在有氧条件下，并在野生型tonB基因的存在下。其他实验室先前的工作表明，tonB在低组成水平表达，无论铁的可用性或毛皮位点的变化。与此相反，这些数据表明，tonB转录抑制三倍的生长在FeCl 3的存在下相比，在铁螯合剂联吡啶的存在下的生长，这种抑制需要的毛皮位点。携带tonB启动子的168个碱基对的DNA片段足以进行所观察到的转录调控。此外，tonB基因似乎有一个比以前认识到的更强的启动子。其他实验室无法检测tonB转录调控似乎是由于铁饥饿tonB菌株的生长极其缓慢，以及使用Mu d1（lac Apr）或λ plac Mu 53产生的融合蛋白编码不耐热的TrpA-LacZ杂合蛋白。这些数据还表明，以前报道的生长期调节tonB只发生在培养基中与中间水平的可用铁，是由于铁饥饿诱导的去阻遏作为文化的方法稳定期。
The tonB gene is required for the transport of several different iron-siderophore complexes across the Escherichia coli outer membrane. In this study, transcriptional regulation of the tonB gene was investigated by using three different tonB-lacZ fusions to monitor tonB expression under aerobic conditions and in the presence of a wild-type tonB gene. Prior work by other laboratories suggests that tonB is expressed at low constitutive levels regardless of changes in iron availability or the fur locus. In contrast, these data show that tonB transcription is repressed threefold by growth in the presence of FeCl3 compared with growth in the presence of the iron chelator dipyridyl and that this repression requires the fur locus. A 168-base-pair DNA fragment carrying the tonB promoter was sufficient for the observed transcriptional regulation. In addition, the tonB gene appeared to have a substantially stronger promoter than previously recognized. The inability of other laboratories to detect tonB transcription regulation appears to be due to the extremely slow growth of iron-starved tonB strains and the use of Mu d1(lac Apr)- or lambda plac Mu53-generated fusions that encode a thermolabile TrpA-LacZ hybrid protein. The data also suggest that the previously reported growth phase regulation of tonB occurs only in media with intermediate levels of available iron and is due to iron starvation-induced derepression as the culture approaches stationary phase.