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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: May 8, 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

Homologous interactions of lambda repressor and lambda Cro with the lambda operator.

A Hochschild, M Ptashne

    Cell
    |March 28, 1986
    PubMed
    Summary
    This summary is machine-generated.

    Lambda repressor and Cro proteins bind similar DNA sites on phage chromosomes. This study reveals that a specific serine in both proteins contacts the same DNA position, explaining their distinct binding affinities.

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    Last Updated: May 8, 2026

    Inducing a Site Specific Replication Blockage in E. coli Using a Fluorescent Repressor Operator System
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    Published on: August 21, 2016

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

    Published on: March 29, 2019

    Area of Science:

    • Molecular Biology
    • Genetics
    • Biochemistry

    Background:

    • Lambda repressor and Cro are proteins that bind to specific DNA sequences on the phage chromosome.
    • They share common binding sites but exhibit different binding affinities.
    • Conserved amino acids in their recognition helices and nucleotides in operator sites suggest a structural basis for their interaction.

    Purpose of the Study:

    • To investigate the role of a conserved serine at position 2 of the recognition alpha-helix in both lambda repressor and Cro.
    • To determine the specific DNA contact point for this serine residue.
    • To refine the understanding of how repressor and Cro recognize similar operator sites with differing affinities.

    Main Methods:

    • Site-directed mutagenesis to alter the serine residue.
    • DNA-binding assays to measure binding affinities.
    • Structural analysis to confirm protein-DNA interactions.

    Main Results:

    • Contrary to previous models, the serine at position 2 of the recognition helix in both repressor and Cro contacts the same conserved nucleotide at position 4 of the operator DNA.
    • This interaction explains the shared recognition of operator sites.
    • Differences in other interactions likely account for their distinct relative affinities.

    Conclusions:

    • The conserved serine residue plays a crucial role in the specific DNA recognition by both lambda repressor and Cro.
    • A simplified model is proposed for the differential binding of these proteins to similar operator sequences.
    • This finding enhances our understanding of protein-DNA interactions and sequence recognition mechanisms.