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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...
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...
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...
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...
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...
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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Related Experiment Video

Updated: Jun 12, 2026

Analyzing and Building Nucleic Acid Structures with 3DNA
16:24

Analyzing and Building Nucleic Acid Structures with 3DNA

Published on: April 26, 2013

Wrapped-around models for the lac operon complex.

Giovanni La Penna1, Angelo Perico

  • 1Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo-Metallici, Sesto Fiorentino, Florence, Italy. glapenna@iccom.cnr.it

Biophysical Journal
|June 17, 2010
PubMed
Summary
This summary is machine-generated.

Protein-DNA interactions in the lac operon show DNA can bend around regulatory proteins. Simulations reveal wrapped-around configurations are favored, with DNA distortion near operators and adaptable protein domains.

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Area of Science:

  • Molecular Biology
  • Biophysics
  • Structural Biology

Background:

  • The lac operon is a model system for studying protein-DNA interactions and DNA structural plasticity.
  • Two models exist for lac operon protein-DNA complexes: wrapped-away and wrapped-around.
  • Understanding DNA bending and protein assembly interactions is crucial for gene regulation studies.

Purpose of the Study:

  • To investigate the structural arrangements of protein-DNA complexes in the lac operon.
  • To determine the preferred configuration of the Lac repressor tetramer relative to the DNA loop.
  • To analyze DNA bending and plasticity induced by protein interactions.

Main Methods:

  • Electrostatic analytical modeling to assess DNA bending potential.
  • Coarse-grained modeling to explore various DNA-protein arrangements.
  • All-atom molecular dynamics simulations for high-resolution structural analysis.

Main Results:

  • Electrostatic models support DNA bending consistent with wrapped-around models.
  • Coarse-grained models indicate a higher propensity for wrapped-around configurations over wrapped-away.
  • All-atom simulations show maintained DNA helical structure between O3-O1 operators, with distortion beyond O1.
  • Protein tetramer N-terminal domains adapt to DNA tension.

Conclusions:

  • The Lac protein tetramer facilitates DNA bending, favoring wrapped-around arrangements.
  • DNA structural changes are localized, with protein domains showing adaptive flexibility.
  • These findings enhance our understanding of DNA plasticity in gene regulation.