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Related Concept Videos

Formation of Lipopolysaccharides01:19

Formation of Lipopolysaccharides

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, triggering...
Oligosaccharide Assembly01:24

Oligosaccharide Assembly

Protein glycosylation starts in the ER lumen and continues in the Golgi apparatus. Glycosyltransferases catalyze the addition of sugar molecules or glycosylation of proteins. Usually, these enzymes add sugars to the hydroxyl groups of selected serine or threonine residues to form O-linked glycans or the amino groups of asparagine residues to form N-linked glycans. Different positions on the same polypeptide chain can contain differently linked glycans.
Multiple sugar molecules that may or may...
Peptidoglycan Synthesis01:28

Peptidoglycan Synthesis

Structure of PeptidoglycanPeptidoglycan is a vital structural component of the bacterial cell wall, providing mechanical strength and shape to the cell. It consists of repeating units of two sugars—N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)—linked by β-1,4 glycosidic bonds. These sugar chains are cross-linked by short peptide chains, forming a mesh-like polymer that surrounds the bacterial plasma membrane.Cytoplasmic Phase – Precursor SynthesisPeptidoglycan biosynthesis begins in...
Protein Glycosylation01:25

Protein Glycosylation

Glycosylation, the most common post-translational modification for proteins, serves diverse functions. Adding sugars to proteins makes the proteins more resistant to proteolytic digestion. Glycosylated proteins can act as markers and receptors to promote cell-cell adhesion. Additionally, they have many essential quality control functions in the cell, such as correct protein folding and facilitating transport of misfolded proteins to the cytosol, which can be degraded.
Glycosylation occurs in...
Proteoglycans01:05

Proteoglycans

Glycans, a class of complex heterogeneous molecules, can be covalently attached to proteins to form glycosylated proteins that regulate various physiological and pathological processes. Glycosylated proteins or glycoproteins comprise N-linked and O-linked oligosaccharides. O-glycosylation is the most common type of protein glycosylation. Here, glycans attach to the oxygen atom of the hydroxyl groups of Serine or Threonine residues. O-linked glycosylation occurs later in protein processing,...
Outer Layers of the Cell Envelope01:18

Outer Layers of the Cell Envelope

The outermost layers of prokaryotic cells play a critical role in their survival, virulence, and interaction with the environment. These layers, often composed of polysaccharides, polypeptides, or proteins, form protective and adhesive structures that vary in organization and function.Capsules and Slime LayersCapsules are highly organized, tightly bound layers that firmly attach to the bacterial cell wall. Capsules are usually made of polysaccharides, though some are made of polypeptides. These...

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Related Experiment Video

Updated: May 15, 2026

Purification and Visualization of Lipopolysaccharide from Gram-negative Bacteria by Hot Aqueous-phenol Extraction
05:31

Purification and Visualization of Lipopolysaccharide from Gram-negative Bacteria by Hot Aqueous-phenol Extraction

Published on: May 28, 2012

Structural Basis of Lipopolysaccharide O-Antigen Chain Length Modality.

Benjamin Wiseman1, Göran Widmalm2, Martin Högbom1

  • 1Department of Biochemistry and Biophysics and Science for Life Laboratory, Stockholm University, Stockholm, Sweden.

Research (Washington, D.C.)
|May 14, 2026
PubMed
Summary

Researchers studied FepE, a protein controlling bacterial O-antigen length. Its structure suggests polysaccharide chains grow inside, released through an opening, aiding immune evasion in gram-negative bacteria.

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Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria
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Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria

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Related Experiment Videos

Last Updated: May 15, 2026

Purification and Visualization of Lipopolysaccharide from Gram-negative Bacteria by Hot Aqueous-phenol Extraction
05:31

Purification and Visualization of Lipopolysaccharide from Gram-negative Bacteria by Hot Aqueous-phenol Extraction

Published on: May 28, 2012

Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria
12:57

Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria

Published on: September 16, 2013

Separation of the Cell Envelope for Gram-negative Bacteria into Inner and Outer Membrane Fractions with Technical Adjustments for Acinetobacter baumannii
10:24

Separation of the Cell Envelope for Gram-negative Bacteria into Inner and Outer Membrane Fractions with Technical Adjustments for Acinetobacter baumannii

Published on: April 10, 2020

Area of Science:

  • Structural Biology
  • Microbiology
  • Biochemistry

Background:

  • Lipopolysaccharides are crucial for gram-negative bacteria, forming the cell envelope and aiding immune evasion.
  • The Wzy-dependent pathway regulates the length of O-antigen polysaccharides, impacting bacterial defense.
  • FepE is identified as the copolymerase enzyme responsible for O-antigen length modulation.

Purpose of the Study:

  • To determine the structure and dynamics of FepE using cryo-electron microscopy.
  • To elucidate the mechanism of O-antigen chain length control.
  • To understand how FepE facilitates polysaccharide release.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) was used to resolve the high-resolution structure of FepE.
  • Comparative analysis of periplasmic domain volumes and hydrated sugar volumes.
  • Observation of large-scale conformational changes within the FepE complex.

Main Results:

  • The study resolved the structure and dynamics of FepE, revealing its role in O-antigen length modulation.
  • Comparison of FepE's periplasmic domain volume with sugar volumes suggests polymerization occurs internally.
  • Mechanistically relevant movements, including complex opening, were observed, creating a pathway for polysaccharide release.

Conclusions:

  • The size of the FepE periplasmic domain likely dictates O-antigen chain length.
  • Polysaccharide polymerization and release occur through dynamic opening and closing of the FepE complex.
  • This mechanism is critical for bacterial cell envelope integrity and immune evasion strategies.