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Related Concept Videos

Mechanism of Conjugation01:19

Mechanism of Conjugation

Bacterial conjugation is a mechanism of horizontal gene transfer that enables the exchange of genetic material between bacterial cells through direct contact. This process is facilitated by a donor cell carrying a conjugative plasmid, which encodes genes necessary for pilus formation, DNA replication, and transfer. The conjugative plasmid plays a central role in initiating and executing the transfer of genetic material.The tra region of the conjugative plasmid encodes proteins responsible for...
Conjugation01:19

Conjugation

Conjugation is a form of horizontal gene transfer that primarily occurs in bacteria and some archaea, promoting genetic diversity and adaptation. Bacteria can acquire resistance genes through conjugative plasmids, allowing them to survive antibiotic treatments that would otherwise be lethal. This process involves direct contact between cells through specialized structures such as the sex pilus and is mediated by conjugative plasmids, including the F (fertility) factor.Conjugation requires...
The Replisome03:01

The Replisome

DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
Plasmids01:28

Plasmids

Plasmids are extrachromosomal DNA molecules found in bacteria, archaea, and some eukaryotic microbes like yeast. These small, circular DNA structures typically contain fewer than 30 genes, although some may exist linearly. Plasmids vary in their number within a cell, known as copy number. Single-copy plasmids are present in one copy per cell and multi-copy plasmids are present in multiple copies, reaching over 100 copies per cell.Plasmids usually replicate independently of the chromosomal DNA...
Coordination of Gene Expression Processes in Bacteria01:29

Coordination of Gene Expression Processes in Bacteria

The DNA replication, transcription, and translation processes are intricately coupled in bacteria, allowing efficient gene expression and rapid protein synthesis. While this physical and functional coordination is advantageous, it introduces challenges that bacteria overcome through specific regulatory mechanisms.Coupling of Replication, Transcription, and TranslationThe coupling of replication, transcription, and translation is a hallmark of bacterial gene expression. As the replisome unwinds...
Conservative Site-specific Recombination and Phase Variation02:53

Conservative Site-specific Recombination and Phase Variation

Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
The recognition sites for Cre recombinase called LoxP...

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Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation
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Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation

Published on: January 4, 2017

Plasmid r1 conjugative DNA processing is regulated at the coupling protein interface.

Sanja Mihajlovic1, Silvia Lang, Marta V Sut

  • 1University of Graz, Institute of Molecular Biosciences, Humboldtstrasse 50, A-8010 Graz, Austria.

Journal of Bacteriology
|September 22, 2009
PubMed
Summary

Selective substrate uptake by type IV secretion systems is regulated by type IV coupling proteins (T4CPs). This study reveals how T4CP TraD interacts with the relaxosome to control DNA transfer initiation in gram-negative bacteria.

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Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation
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Published on: January 4, 2017

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High-Resolution Comparison of Bacterial Conjugation Frequencies
05:18

High-Resolution Comparison of Bacterial Conjugation Frequencies

Published on: January 10, 2019

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Type IV secretion systems (T4SS) in gram-negative bacteria mediate the transfer of various macromolecules.
  • Type IV coupling proteins (T4CPs) are crucial for T4SS function, but their role in substrate uptake and initiation is not fully understood.

Purpose of the Study:

  • To investigate the regulatory interface between the plasmid R1 T4CP (TraD) and its cognate nucleoprotein relaxosome.
  • To elucidate the molecular mechanisms controlling the initiation of DNA processing and substrate presentation for T4SS-mediated export.

Main Methods:

  • Biochemical reconstitution of the T4CP-relaxosome interaction.
  • In vitro analysis of TraD and TraM effects on relaxosome catalytic activities.
  • In vivo and in vitro DNA unwinding assays (e.g., permanganate mapping).

Main Results:

  • The cytosolic domain of T4CP TraD stimulated the DNA transesterase activity of relaxosome component TraI.
  • TraM, a TraD interaction partner, also enhanced TraI activity and induced DNA underwinding in vivo.
  • TraD induced localized DNA unwinding at the origin of transfer (oriT) but did not form an open complex for helicase activity.

Conclusions:

  • The study links relaxosome regulation to T4CPs, suggesting a critical role in initiating DNA export.
  • Activation of TraI helicase loading or catalysis is a committed step in the initiation of DNA export via T4SS.