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Related Concept Videos

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...
Cooperative Binding of Transcription Regulators02:13

Cooperative Binding of Transcription Regulators

Transcriptional regulators bind to specific cis-regulatory sequences in the DNA to regulate gene transcription. These cis-regulatory sequences are very short, usually less than ten nucleotide pairs in length. The short length means that there is a high probability of the exact same sequence randomly occurring throughout the genome.  Since regulators can also bind to groups of similar sequences, this further increases the chances of random binding. Transcriptional regulators form dimers that...
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...
Cooperative Binding of Transcription Regulators02:13

Cooperative Binding of Transcription Regulators

Transcriptional regulators bind to specific cis-regulatory sequences in the DNA to regulate gene transcription. These cis-regulatory sequences are very short, usually less than ten nucleotide pairs in length. The short length means that there is a high probability of the exact same sequence randomly occurring throughout the genome.  Since regulators can also bind to groups of similar sequences, this further increases the chances of random binding. Transcriptional regulators form dimers that...
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...
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...

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Related Experiment Video

Updated: Jun 18, 2026

A Novel Saturation Mutagenesis Approach: Single Step Characterization of Regulatory Protein Binding Sites in RNA Using Phosphorothioates
11:49

A Novel Saturation Mutagenesis Approach: Single Step Characterization of Regulatory Protein Binding Sites in RNA Using Phosphorothioates

Published on: August 21, 2018

Lambda repressor mutations that increase the affinity and specificity of operator binding.

H C Nelson, R T Sauer

    Cell
    |September 1, 1985
    PubMed
    Summary
    This summary is machine-generated.

    Second-site reversion identified mutations enhancing lambda repressor’s DNA binding affinity and specificity. These genetic modifications improve repressor-DNA interactions, offering insights into protein-DNA binding mechanisms.

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    Last Updated: Jun 18, 2026

    A Novel Saturation Mutagenesis Approach: Single Step Characterization of Regulatory Protein Binding Sites in RNA Using Phosphorothioates
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    Area of Science:

    • Molecular Biology
    • Genetics
    • Biochemistry

    Background:

    • Lambda repressor protein regulates viral DNA replication.
    • Understanding protein-DNA interactions is crucial for molecular biology.
    • Second-site reversion is a method to study protein function.

    Purpose of the Study:

    • To identify amino acid substitutions that enhance lambda repressor's binding affinity and specificity to operator DNA.
    • To investigate the structural basis for increased repressor-operator interactions.

    Main Methods:

    • Intragenic, second-site reversion mutagenesis was employed.
    • Purified repressors with substitutions were analyzed for DNA binding.
    • Binding kinetics (association and dissociation rates) were measured.

    Main Results:

    • Second-site substitutions increased repressor-operator DNA binding affinity 3- to 600-fold compared to wild type.
    • Affinity enhancements resulted from faster association and slower dissociation rates.
    • Substitutions in alpha 2 and alpha 3 helices formed new bonds with the DNA backbone.
    • A substitution in the alpha 5 helix indirectly increased operator affinity.

    Conclusions:

    • Second-site reversion is effective in identifying beneficial mutations for protein-DNA binding.
    • Specific amino acid substitutions can significantly enhance repressor-operator interactions through direct or indirect mechanisms.
    • Structural insights suggest targeted modifications can optimize protein-DNA binding affinity and specificity.