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首页> 外文期刊>Journal of bacteriology >The complex bet promoters of Escherichia coli: regulation by oxygen (ArcA), choline (BetI), and osmotic stress.
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The complex bet promoters of Escherichia coli: regulation by oxygen (ArcA), choline (BetI), and osmotic stress.

机译：大肠杆菌的复杂下注启动子：通过氧气（ArcA），胆碱（BetI）和渗透压调节。

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摘要

The bet regulon allows Escherichia coli to synthesize the osmoprotectant glycine betaine from choline. It comprises a regulatory gene, betI, and three structural genes: betT (choline porter), betA (choline dehydrogenase), and betB (betaine aldehyde dehydrogenase). The bet genes are regulated by oxygen, choline, and osmotic stress. Primer extension analysis identified two partially overlapping promoters which were responsible for the divergent expression of the betT and betIBA transcripts. The transcripts were initiated 61 bp apart. Regulation of the promoters was investigated by using cat (chloramphenicol acetyltransferase) and lacZ (beta-galactosidase) operon fusions. Mutation of betI on plasmid F'2 revealed that BetI is a repressor which regulates both promoters simultaneously in response to the inducer choline. Both promoters remained inducible by osmotic stress in a betI mutant background. On the basis of experiments with hns and hns rpoS mutants, we conclude that osmoregulation of the bet promoters was hns independent. The bet promoters were repressed by ArcA under anaerobic growth conditions. An 89-bp promoter fragment, as well as all larger fragments tested, which included both transcriptional start points, displayed osmotic induction and BetI-dependent choline regulation when linked with a cat reporter gene on plasmid pKK232-8. Flanking DNA, presumably on the betT side of the promoter region, appeared to be needed for ArcA-dependent regulation of both promoters.
机译：下注调节子使大肠杆菌能够从胆碱合成渗透保护剂甘氨酸甜菜碱。它包含一个调节基因betI和三个结构基因：betT（胆碱转运蛋白），betA（胆碱脱氢酶）和betB（甜菜碱醛脱氢酶）。下注基因受氧，胆碱和渗透压的调节。引物延伸分析鉴定了两个部分重叠的启动子，其负责betT和betIBA转录本的差异表达。转录本分开61 bp开始。通过使用cat（氯霉素乙酰基转移酶）和lacZ（β-半乳糖苷酶）操纵子融合蛋白来研究启动子的调控。质粒F'2上betI的突变表明BetI是阻遏物，可响应诱导物胆碱同时调节两个启动子。两个启动子在betI突变体背景下均能被渗透压诱导。根据hns和hns rpoS突变体的实验，我们得出结论，下注启动子的渗透调节是hns独立的。在厌氧生长条件下，押注启动子被ArcA抑制。当与质粒pKK232-8上的cat报告基因连接时，一个89 bp的启动子片段以及所有测试的较大片段（包括转录起点）均表现出渗透诱导和BetI依赖性胆碱调节。可能在启动子区域的betT侧的侧翼DNA似乎是两个启动子的ArcA依赖性调节所必需的。

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