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Related Concept Videos

Inducible Operons: lac Operon01:25

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...
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Prokaryotic Transcriptional Activators and Repressors01:58

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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.
Transcription of prokaryotic...
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Prokaryotic Transcriptional Activators and Repressors01:58

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No description available
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Co-activators and Co-repressors02:04

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Gene transcription is regulated by the synergistic action of several proteins that form a complex at a gene regulatory site. This is observed in eukaryotes, where the regulation of gene expression is a complex process. Regulatory proteins in eukaryotes can broadly be classified into two types – regulators that bind directly to specific DNA sequences and co-regulators that associate with regulatory proteins but cannot directly bind to the DNA. These co-regulators are further divided into...
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Operons02:09

Operons

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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...
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Visualization of DNA Repair Proteins Interaction by Immunofluorescence
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Lac repressor-operator interaction: DNA length dependence.

A M Khoury1, H J Lee, M Lillis

  • 1Department of Chemistry, University of Pennsylvania, Philadelphia 19104.

Biochimica Et Biophysica Acta
|September 10, 1990
PubMed
Summary
This summary is machine-generated.

The E. coli lac operon repressor binds DNA differently based on operator length. Short DNA fragments use 3D diffusion, while longer fragments involve 1D sliding and hopping for efficient binding.

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Combining Single-molecule Manipulation and Imaging for the Study of Protein-DNA Interactions
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Area of Science:

  • Molecular Biology
  • Genetics
  • Biophysics

Background:

  • The lac operon in E. coli is a fundamental model for gene regulation.
  • Understanding repressor-DNA interactions is crucial for deciphering gene expression control.

Purpose of the Study:

  • To investigate how DNA length affects the interaction rate between the E. coli lac repressor and its operator DNA.
  • To elucidate the mechanisms governing repressor-operator association.

Main Methods:

  • Direct examination of repressor-operator DNA interactions.
  • Measurement of dissociation equilibrium constant (KD) and dissociation rate constant (kd) using nitrocellulose filter adsorption assays.
  • Calculation of apparent bimolecular association rate constants (ka).

Main Results:

  • Repressor association with short operator DNA (<70 bp) follows rates predicted by three-dimensional diffusion.
  • For longer DNA fragments, association rates suggest a combination of mechanisms.
  • These mechanisms include three-dimensional diffusion, one-dimensional sliding, hopping, and intersegment transfer.

Conclusions:

  • DNA length significantly influences the kinetics of repressor-operator binding in E. coli.
  • Multiple search and binding mechanisms are employed by the repressor depending on DNA fragment size.
  • This study provides insights into the dynamic process of protein-DNA recognition in prokaryotes.