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Inducible Operons: lac Operon

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The lac operon in Escherichia coli is a model for understanding inducible gene regulation and metabolic flexibility. It integrates local control by lactose and global regulation through catabolite repression, enabling E. coli to preferentially metabolize glucose when available and switch to lactose utilization when glucose is scarce.Structure and Function of the lac OperonThe lac operon contains three structural genes: lacZ (β-galactosidase), lacY (lactose permease), and lacA (thiogalactoside...

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Prokaryotes can control gene expression through operons—DNA sequences consisting of regulatory elements and clustered, functionally related protein-coding genes. Operons use a single promoter sequence to initiate transcription of a gene cluster (i.e., a group of structural genes) into a single mRNA molecule. The terminator sequence ends transcription. An operator sequence, located between the promoter and structural genes, prohibits the operon’s transcriptional activity if bound by a repressor...

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The operon model represents a fundamental mechanism of gene regulation in prokaryotes, enabling coordinated expression of genes involved in related metabolic or functional pathways. Operons consist of structural genes, a promoter, and an operator, with transcription regulated by repressors, activators, and small effector molecules.Structure and Function of OperonsAn operon is a cluster of structural genes transcribed together under the control of a single promoter. The promoter region...

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The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes for proteins involved in the same biochemical process or function are located together in groups. This group of genes, along with their regulatory elements, are collectively known as an operon. The functional genes in an operon are transcribed together to give a single strand of mRNA known as polycistronic mRNA.
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Prokaryotic Transcriptional Activators and Repressors

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The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes for proteins involved in the same biochemical process or function are located together in groups. This group of genes, along with their regulatory elements, are collectively known as an operon. The functional genes in an operon are transcribed together to give a single strand of mRNA known as polycistronic mRNA.
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Related Experiment Video

Updated: Jun 27, 2026

In vivo Application of the REMOTE-control System for the Manipulation of Endogenous Gene Expression

In vivo Application of the REMOTE-control System for the Manipulation of Endogenous Gene Expression

Published on: March 29, 2019

Evolving Lac repressor for enhanced inducibility.

O Satya Lakshmi¹, N M Rao

¹Center for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500007, India.

Protein Engineering, Design & Selection : PEDS

|November 26, 2008

Summary

This summary is machine-generated.

Researchers engineered improved lactose repressor (LacI) proteins using directed evolution. These novel LacI mutants function as efficient molecular switches, enhancing gene expression at low inducer concentrations.

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Area of Science:

Molecular Biology
Genetics
Biochemistry

Background:

Lactose repressor (LacI) is a well-characterized prokaryotic transcriptional regulator.
Extensive research has focused on LacI's ligand binding and allosteric response mechanisms.
Understanding LacI's allosteric properties is crucial for gene regulation studies.

Purpose of the Study:

To generate LacI mutants with altered allosteric properties using directed evolution.
To identify LacI variants exhibiting enhanced inducer binding and gene expression.
To develop a robust system for screening LacI mutants.

Main Methods:

Directed evolution techniques, including error-prone PCR and gene shuffling.
Optimization of expression and screening systems for LacI variants.
Selection of mutants based on reporter gene induction at low inducer concentrations.

Main Results:

Four LacI mutants with significantly altered allosteric properties were identified.
These mutants demonstrated reporter gene induction at 1 microM isopropyl beta-D-1-thiogalactopyranoside (IPTG).
Mutant LacI proteins provided 2-10 times higher gene expression levels compared to wild-type.

Conclusions:

Directed evolution successfully generated novel LacI mutants with improved molecular switch capabilities.
The identified mutations offer new insights into LacI allostery and function.
These enhanced LacI variants hold potential for advanced gene expression control systems.