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Updated: Aug 29, 2026

Analysis of Protein Folding, Transport, and Degradation in Living Cells by Radioactive Pulse Chase
Published on: February 12, 2019
Calnexin, calreticulin, and ERp57: teammates in glycoprotein folding
Lars Ellgaard1, Eva-Maria Frickel
1Institute of Biochemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
Abstract:
In eukaryotic cells, the endoplasmic reticulum (ER) plays an essential role in the synthesis and maturation of a variety of important secretory and membrane proteins. For glycoproteins, the ER possesses a dedicated maturation system, which assists folding and ensures the quality of final products before ER release. Essential components of this system include the lectin chaperones calnexin (CNX) and calreticulin (CRT) and their associated co-chaperone ERp57, a glycoprotein specific thiol-disulfide oxidoreductase. The significance of this system is underscored by the fact that CNX and CRT interact with practically all glycoproteins investigated to date, and by the debilitating phenotypes revealed in knockout mice deficient in either gene. Compared to other important chaperone systems, such as the Hsp70s, Hsp90s and GroEL/GroES, the principles whereby this system works at the molecular level are relatively poorly understood. However, recent structural and biochemical data have provided important new insights into this chaperone system and present a solid basis for further mechanistic studies.
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