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Related Concept Videos

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...
Protein Folding Quality Check in the RER01:29

Protein Folding Quality Check in the RER

ER is the primary site for the maturation and folding of soluble and transmembrane secretory proteins. The calnexin cycle is a specific chaperone system that folds and assesses the confirmation of N-glycosylated proteins before they can exit the ER lumen. The primary players of this quality check pipeline are the lectins, ER-resident chaperones, and a glucosyl transferase enzyme. In case the calnexin system in the lumen fails to salvage a misfolded protein, it is transported to the cytoplasm...
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...
Protein Modifications in the RER01:26

Protein Modifications in the RER

Modification of secretory and transmembrane proteins entering the rough ER begins in the ER lumen. These modifications aid in protein folding and stabilize the acquired tertiary structure. Protein modifications in the rough ER co-occur at different stages of protein folding.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
Export of Misfolded Proteins out of the ER01:32

Export of Misfolded Proteins out of the ER

After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
ER Retrieval Pathway01:45

ER Retrieval Pathway

In the secretory pathway, vesicles transport proteins from one cellular compartment to another in forward transport to deliver the protein to its correct location. Occasionally, misfolded proteins and incorrect proteins escape their original compartments, and a retrieval pathway is used to return the escaped proteins to their original compartment.
The ER uses many checkpoints to prevent the entry of incorrectly folded or a resident protein as cargo onto a transport vesicle. These mechanisms...

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Related Experiment Video

Updated: Jun 19, 2026

Pulse-chase Analysis of N-linked Sugar Chains from Glycoproteins in Mammalian Cells
10:17

Pulse-chase Analysis of N-linked Sugar Chains from Glycoproteins in Mammalian Cells

Published on: April 27, 2010

N-glycan structures: recognition and processing in the ER.

Markus Aebi1, Riccardo Bernasconi, Simone Clerc

  • 1Institute of Microbiology, Department of Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland. markus.aebi@micro.biol.ethz.ch

Trends in Biochemical Sciences
|October 27, 2009
PubMed
Summary
This summary is machine-generated.

The endoplasmic reticulum (ER) uses N-linked glycans as a "glyco-code" to manage protein folding and quality control. Understanding this code is key to regulating protein homeostasis for clinical and industrial uses.

More Related Videos

Identification and Characterization of Protein Glycosylation using Specific Endo- and Exoglycosidases
09:54

Identification and Characterization of Protein Glycosylation using Specific Endo- and Exoglycosidases

Published on: December 26, 2011

Related Experiment Videos

Last Updated: Jun 19, 2026

Pulse-chase Analysis of N-linked Sugar Chains from Glycoproteins in Mammalian Cells
10:17

Pulse-chase Analysis of N-linked Sugar Chains from Glycoproteins in Mammalian Cells

Published on: April 27, 2010

Identification and Characterization of Protein Glycosylation using Specific Endo- and Exoglycosidases
09:54

Identification and Characterization of Protein Glycosylation using Specific Endo- and Exoglycosidases

Published on: December 26, 2011

Area of Science:

  • Biochemistry
  • Cell Biology
  • Glycoscience

Background:

  • Secretory protein homeostasis in eukaryotic cells relies on N-linked glycan processing.
  • The endoplasmic reticulum (ER) utilizes molecular chaperones and enzymes for glycoprotein folding and degradation.
  • Specific oligosaccharide structures on N-linked glycans recruit these ER components.

Purpose of the Study:

  • To elucidate the role of N-linked glycan modification in the ER protein quality control system.
  • To understand how specific oligosaccharide structures direct protein fate.
  • To explore the implications of deciphering the ER's

Main Methods:

  • Identification of novel components involved in N-linked glycan modification within the ER.
  • Analysis of oligosaccharide structures generated by these components.
  • Investigation of lectin recognition of modified glycans and subsequent protein trafficking.

Main Results:

  • Several new components of the ER protein quality control system that modify N-linked glycans have been identified.
  • These modifications generate specific oligosaccharide structures.
  • These structures are recognized by carbohydrate-binding proteins (lectins), which direct protein fate.

Conclusions:

  • N-linked glycan processing acts as a critical regulatory mechanism for secretory protein homeostasis.
  • The ER's