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Biochemical Society Transactions Apr 2019The operon promoter is widely used as a tool to control recombinant protein production in bacteria. Here, we give a brief review of how it functions, how it is... (Review)
Review
The operon promoter is widely used as a tool to control recombinant protein production in bacteria. Here, we give a brief review of how it functions, how it is regulated, and how, based on this knowledge, a suite of promoter derivatives has been developed to give a controlled expression that is suitable for diverse biotechnology applications.
Topics: Escherichia coli; Lac Operon; Promoter Regions, Genetic; Recombinant Proteins; Repressor Proteins; Transcription, Genetic
PubMed: 30971435
DOI: 10.1042/BST20190059 -
Journal of Biotechnology Jan 2012Most commonly used expression systems in bacteria are based on the Escherichia coli lac promoter. Furthermore, lac operon elements are used today in systems and... (Comparative Study)
Comparative Study
Most commonly used expression systems in bacteria are based on the Escherichia coli lac promoter. Furthermore, lac operon elements are used today in systems and synthetic biology. In the majority of the cases the gratuitous inducers IPTG or TMG are used. Here we report a systematic comparison of lac promoter induction by TMG and IPTG which focuses on the aspects inducer uptake, population heterogeneity and a potential influence of the transacetylase, LacA. We provide induction curves in E. coli LJ110 and in isogenic lacY and lacA mutant strains and we show that both inducers are substrates of the lactose permease at low inducer concentrations but can also enter cells independently of lactose permease if present at higher concentrations. Using a gfp reporter strain we compared TMG and IPTG induction at single cell level and showed that bimodal induction with IPTG occurred at approximately ten-fold lower concentrations than with TMG. Furthermore, we observed that lac operon induction is influenced by the transacetylase, LacA. By comparing two Plac-gfp reporter strains with and without a lacA deletion we could show that in the lacA(+) strain the fluorescence level decreased after few hours while the fluorescence further increased in the lacA(-) strain. The results indicate that through the activity of LacA the IPTG concentration can be reduced below an inducing threshold concentration-an influence that should be considered if low inducer amounts are used.
Topics: Acetyltransferases; Cell Count; Escherichia coli; Escherichia coli Proteins; Green Fluorescent Proteins; Isopropyl Thiogalactoside; Lac Operon; Methylgalactosides; Microscopy, Fluorescence; Monosaccharide Transport Proteins; Protein Engineering; Recombinant Proteins; Symporters; Thiogalactosides; beta-Galactosidase
PubMed: 22079752
DOI: 10.1016/j.jbiotec.2011.10.009 -
Annual International Conference of the... Nov 2021Gene regulation is an essential process for cell development, having a profound effect in dictating cell functions. Bacterial genes are often regulated through inducible...
Gene regulation is an essential process for cell development, having a profound effect in dictating cell functions. Bacterial genes are often regulated through inducible systems like the Lac operon which plays an important role in cell metabolism. An accurate model of its regulation can reveal the dynamics of gene expression. In this paper, a mathematical model of this system is constructed by focusing on regulation by the Lac repressor. The results show, as expected, that the concentration of lactose approaches zero while glucose concentration approaches the initial concentration of lactose by the action of β-galactosidase, expressed by the Lac operon. Addition of PD control improves stability of the system, with the phase margin increasing from 45° to 90°. Modeling the dynamics of gene expression in inducible operons like Lac operon can be essential for its applications in the production of recombinant proteins and its potential usage in gene therapy.
Topics: Escherichia coli; Gene Expression; Lac Operon; Lactose; Operon
PubMed: 34891476
DOI: 10.1109/EMBC46164.2021.9630940 -
Journal of Molecular Biology Jul 2013The ability to regulate gene expression is essential for controlling metabolic events in a cell. Proteins that function like molecular switches respond to fluctuations... (Review)
Review
The ability to regulate gene expression is essential for controlling metabolic events in a cell. Proteins that function like molecular switches respond to fluctuations in the environment to maintain homeostasis. The operon model, proposed by Jacob and Monod, provides a cogent depiction for how gene expression is regulated. A molecular mechanism for the regulation followed shortly with the theory for allosteric transition. Over the past half-century, the details of the lac operon and the allosteric model have been tested using genetic, biochemical, and structural techniques. Remarkably, the principles originally put forward 50 years ago remain essentially unchanged. Models for the operon and the theory of allosteric transitions are two of the most profound discoveries of molecular biology.
Topics: Allosteric Regulation; Biochemistry; Chemistry; Gene Expression Regulation; History, 20th Century; History, 21st Century; Lac Operon; Microbiology; Models, Biological; Models, Molecular; Molecular Biology
PubMed: 23500493
DOI: 10.1016/j.jmb.2013.03.003 -
Current Opinion in Structural Biology Feb 1997For many years the lac operon of Escherichia coli has been the paradigm for gene regulation. Recently, the structures of the lac repressor core bound to... (Review)
Review
For many years the lac operon of Escherichia coli has been the paradigm for gene regulation. Recently, the structures of the lac repressor core bound to isopropyl-beta-D-1-thiogalactoside (IPTG), the intact apo lac repressor, the intact lac repressor complexes with IPTG and a 21-base-pair symmetric operator, and the refined headpiece of the repressor have been determined. These structures have provided a framework for understanding a wealth of biochemical and genetic information. An analysis of these structures, as well as a description of their function and a comparison to homologous proteins, is now possible.
Topics: Allosteric Regulation; Bacterial Proteins; Binding Sites; Escherichia coli Proteins; Lac Operon; Lac Repressors; Protein Binding; Repressor Proteins
PubMed: 9032054
DOI: 10.1016/s0959-440x(97)80010-3 -
The Journal of Cell Biology May 2003We use the lac operon in Escherichia coli as a prototype system to illustrate the current state, applicability, and limitations of modeling the dynamics of cellular... (Review)
Review
We use the lac operon in Escherichia coli as a prototype system to illustrate the current state, applicability, and limitations of modeling the dynamics of cellular networks. We integrate three different levels of description (molecular, cellular, and that of cell population) into a single model, which seems to capture many experimental aspects of the system.
Topics: Animals; Computational Biology; Escherichia coli; Humans; Lac Operon; Lactose; Models, Biological; Nonlinear Dynamics
PubMed: 12743100
DOI: 10.1083/jcb.200301125 -
Annual Review of Microbiology 2013I recount the history of how I became interested in the use of gene fusions for studying biological problems. Initially, selections for mutations that would restore... (Review)
Review
I recount the history of how I became interested in the use of gene fusions for studying biological problems. Initially, selections for mutations that would restore function to an inactivated lac operon unexpectedly yielded fusions in which lac was expressed from the controlling elements of upstream genes. Subsequently, by chance, I generated strains in which the lac operon was transposed from its normal position on the chromosome to a position close to the trp operon, thus facilitating sets of useful fusions of the two operons. The development of a more generalized technique for obtaining fusions by my student Malcolm Casadaban opened up a much broader set of biological problems that could be approached with fusions. Work on these problems included the study of protein translocation across membranes, the analysis of membrane protein topology, and the discovery of the pathway of electron transfer that leads to disulfide bond formation in proteins.
Topics: Escherichia coli; Gene Expression Regulation, Bacterial; Gene Fusion; Genetic Techniques; History, 20th Century; History, 21st Century; Lac Operon; Mutagenesis, Insertional
PubMed: 24024632
DOI: 10.1146/annurev-micro-092412-155732 -
Biochemistry and Molecular Biology... Jul 2022Here, we describe a free, web-based simulation of the lac operon, "LacOp," that is designed to enhance the learning of prokaryotic gene regulation and pathways in...
Here, we describe a free, web-based simulation of the lac operon, "LacOp," that is designed to enhance the learning of prokaryotic gene regulation and pathways in advanced high school and undergraduate genetics courses. This new electronic resource was created by a team of students in an advanced undergraduate course and is hosted online (http://flask-env.rnwhymamqf.us-west-2.elasticbeanstalk.com/lacop). LacOp has a simple web interface compatible with a range of devices, including smartphones. To determine whether the LacOp simulation enhances student learning from traditional instruction, we introduced the lac operon to undergraduate genetics students through a traditional classroom experience followed by use of the LacOp simulation. Students worked on their own using the included tutorial to create and test the effect of various genotypes on E. coli lactose metabolism and regulation. Upon completion of the tutorial, students showed measurable gains in conceptual understanding of the lac operon. These students also reported a generally favorable opinion of the LacOP simulation as a use of their instructional time.
Topics: Computer Simulation; Escherichia coli; Humans; Internet; Lac Operon; Students
PubMed: 35723033
DOI: 10.1002/bmb.21638 -
CBE Life Sciences Education 2016Concept inventories (CIs) are valuable tools for educators that assess student achievement and identify misconceptions held by students. Results of student responses can...
Concept inventories (CIs) are valuable tools for educators that assess student achievement and identify misconceptions held by students. Results of student responses can be used to adjust or develop new instructional methods for a given topic. The regulation of gene expression in both prokaryotes and eukaryotes is an important concept in genetics and one that is particularly challenging for undergraduate students. As part of a larger study examining instructional methods related to gene regulation, the authors developed a 12-item CI assessing student knowledge of the lac operon. Using an established protocol, the authors wrote open-ended questions and conducted in-class testing with undergraduate microbiology and genetics students to discover common errors made by students about the lac operon and to determine aspects of item validity. Using these results, we constructed a 12-item multiple-choice lac operon CI called the Lac Operon Concept Inventory (LOCI), The LOCI was reviewed by two experts in the field for content validity. The LOCI underwent item analysis and was assessed for reliability with a sample of undergraduate genetics students (n = 115). The data obtained were found to be valid and reliable (coefficient alpha = 0.994) with adequate discriminatory power and item difficulty.
Topics: Educational Measurement; Female; Humans; Lac Operon; Male; Pilot Projects; Reproducibility of Results; Students; Thinking
PubMed: 27252300
DOI: 10.1187/cbe.15-07-0162 -
Trends in Genetics : TIG Feb 1988
Topics: Animals; Escherichia coli; Gene Expression Regulation; Lac Operon
PubMed: 3072716
DOI: 10.1016/0168-9525(88)90062-5