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Related Concept Videos

Protein Translocation Machinery on the ER Membrane01:28

Protein Translocation Machinery on the ER Membrane

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The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the...
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Gram-negative Bacterial Protein Secretion Systems01:17

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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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Cotranslational Protein Translocation01:20

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Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
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Bacterial Translocation and Protein Secretion01:26

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Bacterial protein secretion involves translocation systems to ensure proteins reach their designated locations, including the plasma membrane, periplasm, outer membrane, or the external environment. These translocation systems are vital for bacterial physiology, supporting processes like membrane assembly, enzymatic activity in the periplasm, and interactions with the external environment. The division of labor between Sec and Tat pathways ensures efficiency in handling proteins with diverse...
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Protein Transport to the Outer Chloroplast Membrane01:11

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Chloroplast outer membrane proteins encoded by the nucleus are synthesized in the cytosol. Soon after synthesis, they bind cytosolic factors such as 14-3-3 protein and the Hsp70 chaperones that keep these precursors in an unfolded state until their translocation.
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Post-translational Translocation of Proteins to the RER01:27

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A sizable fraction of proteins destined for ER are first synthesized in the cell cytosol and then transported across the ER membrane–a process called post-translational translocation. Similar to cotranslationally translocated proteins, these proteins also use the Sec translocon complex to enter the ER lumen.
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Related Experiment Video

Updated: Apr 21, 2026

Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking
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A gatekeeper chaperone complex directs translocator secretion during type three secretion.

Tara L Archuleta1, Benjamin W Spiller2

  • 1Chemical and Physical Biology Program, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America.

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Type Three Secretion Systems (T3SS) use gatekeeper proteins to regulate effector and translocator secretion in Gram-negative bacteria. This study reveals the Chlamydial gatekeeper CopN

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Area of Science:

  • Microbiology
  • Structural Biology
  • Molecular Biology

Background:

  • Gram-negative bacteria utilize Type Three Secretion Systems (T3SS) for host cell invasion.
  • T3SS function relies on a specific secretion order: needle components, translocators, then effectors.
  • Gatekeeper proteins are crucial for T3SS regulation but their mechanism remains unclear.

Purpose of the Study:

  • To elucidate the mechanism of gatekeeper proteins in regulating T3SS secretion.
  • To determine the structural basis for gatekeeper interaction with translocator chaperones and translocators.

Main Methods:

  • X-ray crystallography to determine the structure of the Chlamydial gatekeeper CopN bound to a translocator-specific chaperone.
  • Structure-based mutagenesis in Shigella to investigate the functional significance of the identified complex.

Main Results:

  • The structure reveals a novel interface between gatekeepers and translocator chaperones.
  • The gatekeeper-chaperone complex maintains an open translocator-binding groove.
  • Mutagenesis confirmed the essential role of the gatekeeper-chaperone-translocator complex in ordered secretion.

Conclusions:

  • The gatekeeper-chaperone complex facilitates translocator secretion by keeping the binding groove accessible.
  • This mechanism ensures the correct temporal order of translocator and effector secretion via T3SS.
  • The findings provide critical insights into the regulation of bacterial protein secretion systems.