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Related Concept Videos

Gram-negative Bacterial Protein Secretion Systems01:17

Gram-negative Bacterial Protein Secretion Systems

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Gram-negative bacteria utilize sophisticated protein secretion systems to transport proteins across their double-membrane envelope into the extracellular environment or host cells. Based on their mechanism of action, these systems are classified into one-step and two-step pathways.One-Step Secretion Systems (Types I, III, IV, and VI)One-step secretion systems bypass the periplasm entirely, forming a continuous channel that spans both the inner and outer membranes:Type I Secretion System (T1SS):...
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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...
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Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin,...
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Related Experiment Video

Updated: Aug 4, 2025

Applying Live Cell Imaging and Cryo-Electron Tomography to Resolve Spatiotemporal Features of the Legionella pneumophila Dot/Icm Secretion System
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Applying Live Cell Imaging and Cryo-Electron Tomography to Resolve Spatiotemporal Features of the Legionella pneumophila Dot/Icm Secretion System

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Structure and Function of the Dot/Icm T4SS.

Przemysław Dutka1,2, Yuxi Liu1, Stefano Maggi1,3

  • 1Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA.

Biorxiv : the Preprint Server for Biology
|March 30, 2023
PubMed
Summary
This summary is machine-generated.

Researchers built a near-complete model of the Legionella pneumophila Dot/Icm type IV secretion system (T4SS). This reveals the structure and function of key components, advancing understanding of bacterial infection mechanisms.

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Applying Live Cell Imaging and Cryo-Electron Tomography to Resolve Spatiotemporal Features of the Legionella pneumophila Dot/Icm Secretion System
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Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation
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Area of Science:

  • Microbiology
  • Structural Biology
  • Molecular Biology

Background:

  • The Dot/Icm type IV secretion system (T4SS) of *Legionella pneumophila* is crucial for delivering effector proteins into host cells.
  • Understanding the T4SS atomic structure is vital for developing therapeutic strategies, but current knowledge is limited to isolated subcomplexes.

Approach:

  • Utilized subtomogram averaging and integrative modeling to construct a near-complete model of the Dot/Icm T4SS.
  • Incorporated seventeen protein components into the structural model.
  • Analyzed compositional heterogeneity and integrated *in situ* infection data.

Key Points:

  • A near-complete model of the Dot/Icm T4SS was generated, encompassing seventeen protein components.
  • The structure and function of six novel components (DotI, DotJ, DotU, IcmF, IcmT, IcmX) were elucidated.
  • Interactions between IcmF, DotU, DotO, DotI, and DotJ were detailed, explaining the connection between cytoplasmic and periplasmic domains.

Conclusions:

  • The study provides significant insights into the structural organization and functional mechanisms of the Dot/Icm T4SS.
  • The developed model advances our understanding of T4SS-mediated protein secretion during *Legionella* infection.
  • This work lays the foundation for future research targeting the T4SS as a drug target.