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Related Concept Videos

DNA Bacteriophages01:26

DNA Bacteriophages

Bacteriophages, or phages, are viruses that specifically infect bacteria, utilizing their genetic material to hijack host cellular machinery for replication. DNA bacteriophages employ single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA) genomes. These phages exhibit diverse replication strategies and host interactions, influencing their ecological roles and applications in biotechnology and medicine.ssDNA BacteriophagesssDNA phages, with their small genomes, utilize unique strategies to...
Viral Replication: Lysogenic Cycle01:16

Viral Replication: Lysogenic Cycle

The lysogenic cycle is a crucial viral replication strategy that allows bacteriophages to persist within host cells without immediately destroying them. This process is primarily observed in temperate phages, such as bacteriophage lambda (λ), which infects Escherichia coli. The cycle allows the viral genome to persist across bacterial generations while keeping host cells viable.Integration of the Viral GenomeUpon infection, bacteriophage lambda attaches to the bacterial surface and injects its...
Lysogenic Cycle of Bacteriophages00:43

Lysogenic Cycle of Bacteriophages

In contrast to the lytic cycle, phages infecting bacteria via the lysogenic cycle do not immediately kill their host cell. Instead, they combine their genome with the host genome, allowing the bacteria to replicate the phage DNA along with the bacterial genome. The incorporated copy of the phage genome is called the prophage. Some prophages can re-activate and enter the lytic cycle. This often occurs in response to a perturbation, such as DNA damage, but can also transpire in the absence of...
Lytic Cycle of Bacteriophages01:30

Lytic Cycle of Bacteriophages

Bacteriophages, also known as phages, are specialized viruses that infect bacteria. A key characteristic of phages is their distinctive “head-tail” morphology. A phage begins the infection process (i.e., lytic cycle) by attaching to the outside of a bacterial cell. Attachment is accomplished via proteins in the phage tail that bind to specific receptor proteins on the outer surface of the bacterium. The tail injects the phage’s DNA genome into the bacterial cytoplasm. In the lytic replication...
Viral Replication: Lytic Cycle01:20

Viral Replication: Lytic Cycle

Bacteriophages, or phages, are viruses that specifically infect bacteria. Among them, T-even bacteriophages, such as T4, exhibit a well-characterized lytic replication cycle in Escherichia coli (E. coli). This process ensures the rapid proliferation of the virus while ultimately leading to the destruction of the bacterial host.Attachment and DNA InjectionThe infection process begins with the recognition and binding of the T4 phage to the E. coli cell surface. Tail fibers of the phage...

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Following Cell-fate in E. coli After Infection by Phage Lambda
06:10

Following Cell-fate in E. coli After Infection by Phage Lambda

Published on: October 14, 2011

Purification of bacteriophage lambda repressor.

Ning Gao1, Keith Shearwin, John Mack

  • 1Physics Department, Emory University, 400 Dowman Dr., Atlanta, GA 30322, United States.

Protein Expression and Purification
|July 9, 2013
PubMed
Summary
This summary is machine-generated.

Bacteriophage lambda repressor protein mediates DNA looping essential for viral life cycles. A purified loss-of-cooperativity mutant specifically bound DNA but failed to form loops, revealing key insights into repressor function.

Keywords:
Ammonium sulfateAnion exchangeBacteriophage lambdaHeparin affinityHis-tagLambda repressorSingle particle trackingTethered particle motion

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Last Updated: May 10, 2026

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Published on: October 14, 2011

Visualizing the Interaction Between the Qdot-labeled Protein and Site-specifically Modified λ DNA at the Single Molecule Level
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Isolation and Genome Analysis of Single Virions using 'Single Virus Genomics'
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Isolation and Genome Analysis of Single Virions using 'Single Virus Genomics'

Published on: May 26, 2013

Area of Science:

  • Molecular Biology
  • Virology
  • Biochemistry

Background:

  • Bacteriophage lambda repressor protein regulates the switch between lysogeny and lytic growth in E. coli post-infection.
  • Understanding DNA looping mediated by this repressor is crucial for deciphering viral genetic control mechanisms.

Purpose of the Study:

  • To detail the DNA looping mechanism mediated by bacteriophage lambda repressor.
  • To purify tag-free repressor and a loss-of-cooperativity mutant for functional analysis.

Main Methods:

  • Protein expression and purification using ammonium sulfate fractionation, anion-exchange chromatography, and heparin affinity chromatography.
  • Tethered particle motion (TPM) looping assays.
  • Atomic force microscopy (AFM) footprinting assays.

Main Results:

  • Wild-type and His-tagged lambda repressor specifically bound high-affinity sites and mediated DNA loop formation.
  • A G147D loss-of-cooperativity mutant also bound specifically to DNA but was unable to secure loops.
  • The purification method yielded highly pure protein in good yield using readily available chromatography resins.

Conclusions:

  • Bacteriophage lambda repressor's ability to form DNA loops is critical for its function in regulating viral life cycles.
  • The G147D mutation disrupts the protein's capacity to stabilize DNA loops, highlighting the importance of cooperativity in repressor activity.