发布: 2020年01月20日第10卷第2期 DOI: 10.21769/BioProtoc.3500 浏览次数: 4688
评审: Juan Facundo Rodriguez AyalaJose Antonio Reyes-DariasJan-Ulrik Dahl
Abstract
The reporter system is widely used technique for measuring promoter activity in bacterial cells. Until now, a number of reporter system have been developed, but the bioluminescent reporter constructed from the bacterial luciferase genes is one of the useful systems for measuring in vivo dynamics of gene expression. The introduced bioluciferase lux reporter enables easy, fast, and sensitive measurement of the promoter activity without cell lysis because the substrates of bioluminescent reaction are synthesized inside the bacterial cell, thereby allowing low-cost experiments. This protocol describes a high throughput technique to measure the promoter activity in Escherichia coli K-12 using the lux reporter system.
Keywords: lux operon (lux 操纵子)Background
The promoter activity in vivo was measured using a reporter system such as the lacZ (encoding β-galactosidase), gus (encoding β-gulucuronidase), and cat (encoding chloramphenicol acetyltransferase) genes. In the case of the lacZ reporter system, for instance, the test promoter sequence is fused to a promoter-less lacZ gene, creating a test promoter-lacZ fusion gene, which is then transferred into a recipient cell. For the measurement of the activity of the test promoter, however, the whole cell lysate must be prepared to detect in vitro β-galactosidase activity by adding a substrate such as ONPG (O-Nitrophenyl-β-D-galactopyranoside). To avoid such biochemical procedures, the fluorescent gfp gene, coding green fluorescent protein (GFP), was employed as a reporter which can be detected without cell lysis. Thus, the fluorescent reporter system is more convenient than the systems which requires measurement of enzymatic activity. However, the fluorescent proteins have a technical limitation especially in genes that are expressed at low levels because of high background noise that arises from intrinsic autofluorescence of cells. To overcome this problem, the luminescent reporter has been developed, which catalyzes bioluminescence reactions using the substrate as luciferins (Meighen, 1991). The Photorhabdus luminescens bioluminescence luxCDABE genes, coding two luciferase subunits (LuxAB) and three proteins (LuxCDE), which are important for substrate biosynthesis (Bjarnason et al., 2003). Once the test promoter is fused to promoter-less luxCDABE, both luciferase and its substrate are expressed under the control of the test promoter, and the promoter activity can be easily determined by measuring luminescence without the cell lysis (Bjarnason et al., 2003). This bioluminescent reporter system is recognized as a powerful high-throughput assay for studying continuous kinetics of promoter activity (Yamanaka et al., 2018; Burton et al., 2010). In this protocol, we describe how to construct the bioluminescent reporter system and how to measure the promoter activity in E. coli.
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© 2020 The Authors; exclusive licensee Bio-protocol LLC.
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分类
微生物学 > 微生物遗传学 > 基因表达
分子生物学 > DNA > 基因表达
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