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Related Concept Videos

Inducible Operons: lac Operon01:25

Inducible Operons: lac Operon

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...
Operon Model01:23

Operon Model

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...
Operons02:09

Operons

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...
Repressible Operon: trp Operon01:21

Repressible Operon: trp Operon

The trp operon in Escherichia coli exemplifies a repressible operon. It regulates the synthesis of tryptophan through repressor-mediated transcriptional control and attenuation. This dual regulatory mechanism ensures tryptophan biosynthesis occurs only when needed, conserving cellular resources.Structure of the trp OperonThe trp operon consists of five structural genes (trpE, trpD, trpC, trpB, and trpA) that encode enzymes for tryptophan biosynthesis. These genes are transcribed as a single...
Stringent Response in E. coli01:23

Stringent Response in E. coli

Bacterial growth is closely tied to nutrient availability, with cells proliferating exponentially under favorable conditions and entering a stationary phase when resources become scarce. This transition is mediated by a regulatory mechanism known as the stringent response, which allows bacteria to adapt to nutrient deprivation by modulating gene expression and metabolic activity.During nutrient scarcity, intracellular amino acid levels decline. It results in the accumulation of uncharged tRNAs...
Prokaryotic Transcriptional Activators and Repressors01:58

Prokaryotic Transcriptional Activators and Repressors

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.
Transcription of prokaryotic...

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Updated: Jun 14, 2026

Inducing a Site Specific Replication Blockage in E. coli Using a Fluorescent Repressor Operator System
11:19

Inducing a Site Specific Replication Blockage in E. coli Using a Fluorescent Repressor Operator System

Published on: August 21, 2016

Comparing native and irradiated E. coli lactose repressor-operator complex by molecular dynamics simulation.

Samia Aci-Sèche1, Norbert Garnier, Stéphane Goffinont

  • 1Centre de Biophysique Moléculaire, UPR 4301, CNRS (affiliated to the University of Orléans and to INSERM), Orléans, France.

European Biophysics Journal : EBJ
|March 30, 2010
PubMed
Summary
This summary is machine-generated.

Gamma irradiation destabilizes the E. coli lactose repressor-operator complex by oxidizing tyrosine residues. Molecular dynamics simulations reveal this oxidation increases complex flexibility and reduces DNA-protein interactions, explaining repressor inactivation.

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Area of Science:

  • Molecular Biology
  • Biophysics
  • Radiation Biology

Background:

  • The E. coli lactose operon relies on repressor-operator DNA binding for regulation.
  • Previous studies showed gamma irradiation destabilizes this complex by impairing repressor DNA-binding ability.
  • Tyrosine oxidation in repressor headpieces was proposed as the cause of inactivation.

Purpose of the Study:

  • To elucidate the molecular mechanisms of repressor-operator complex destabilization due to tyrosine oxidation.
  • To compare the native and tyrosine-oxidized repressor-operator complexes using molecular dynamics simulations.

Main Methods:

  • Molecular dynamics (MD) simulations were employed.
  • Two complexes were simulated: native (two headpieces and operator DNA) and damaged (tyrosines replaced with DOPA).
  • Simulations were conducted on a 20 ns timescale.

Main Results:

  • Simulations showed increased flexibility and DNA bending in the damaged complex.
  • Alterations in the hydrogen bond network and decreased electrostatic potential were observed.
  • A reduction in the global energy of DNA-protein interactions was noted.

Conclusions:

  • Tyrosine oxidation significantly destabilizes the repressor-operator complex.
  • MD simulations provide mechanistic insights into radiation-induced inactivation of DNA-binding proteins.