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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
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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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Protein Complex Assembly02:41

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Proteins can form homomeric complexes with another unit of the same protein or heteromeric complexes with different types.  Most protein complexes self-assemble spontaneously via ordered pathways, while some proteins need assembly factors that guide their proper assembly. Despite the crowded intracellular environment, proteins usually interact with their correct partners and form functional complexes.
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Formation of Lipopolysaccharides01:19

Formation of Lipopolysaccharides

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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: Nov 28, 2025

Analyzing Dynamic Protein Complexes Assembled On and Released From Biolayer Interferometry Biosensor Using Mass Spectrometry and Electron Microscopy
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Assembly and Function of the Anthrax Toxin Protein Translocation Complex.

Robert C Liddington1

  • 1, 7602 ½ Eads Ave., La Jolla, CA, 92037, USA. btblidders@gmail.com.

Sub-Cellular Biochemistry
|November 30, 2020
PubMed
Summary

Bacillus anthracis toxin assembly on host cells is key to anthrax infection. Researchers detail the protective antigen

Keywords:
AnthraxConformational changeMacromolecular assemblyPathogenesisProtein translocationStructurepH trigger

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Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Bacillus anthracis is a Gram-positive bacterium causing anthrax, a disease of livestock and a potential bioterrorism agent.
  • Anthrax toxin is a primary virulence factor, with spores being highly stable and deadly if untreated.
  • While intracellular pathways are understood, the focus here is on toxin assembly and delivery.

Purpose of the Study:

  • To elucidate the assembly of secreted anthrax toxins on host cell surfaces.
  • To explain the mechanism of toxin delivery into the host cell cytosol.
  • To integrate structural and biophysical data to understand the infectious process.

Main Methods:

  • Analysis of atomic structures of toxin assembly intermediates and final complexes.
  • Biophysical studies to investigate toxin assembly dynamics.
  • Mutational and biochemical analyses to probe protein interactions.

Main Results:

  • The protective antigen (PA) self-oligomerizes and complexes with lethal factor (LF) or edema factor (EF).
  • PA binds host receptor CMG2, initiating receptor-mediated endocytosis.
  • Toxin delivery into the cytosol is powered by the pH gradient across the membrane.

Conclusions:

  • Atomic structures and biophysical data reveal the choreographed assembly of anthrax toxin.
  • The process demonstrates an elegant and powerful mechanism for enzyme delivery.
  • Understanding this process is crucial for developing targeted interventions against anthrax.