13343 IUPAC Gold Book - invariant chain 10.1351/goldbook.13343 13343 current synonym: CD74 1 Protein (\(\pu{31 kDa}\)) of the endoplasmic reticulum lumen that binds to newly formed major histocompatibility complex (MHC) heterodimeric proteins, preventing binding of endogenous peptides to their groove. This protein acts as a chaperone for these molecules until they leave the Golgi apparatus and enter the endosome pathway. It is degraded proteolytically but leaves a fragment (called CLIP) bound within the groove of the major histocompatibility complex (MHC) class III molecules. In acid vesicles, after leaving the Golgi apparatus, CLIP exchanges with peptides derived from exogenous antigens. endosome https://goldbook.iupac.org//terms/view/13111 major histocompatibility complex (MHC) https://goldbook.iupac.org//terms/view/13430 major histocompatibility complex (MHC) class III molecules https://goldbook.iupac.org//terms/view/13433 PAC, 2012, 84, 1113. 'IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)' on page 1196 (https://doi.org/10.1351/PAC-REC-11-06-03) https://goldbook.iupac.org/terms/view/13343/html https://goldbook.iupac.org/terms/view/13343/json https://goldbook.iupac.org/terms/view/13343/plain Citation: 'invariant chain' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.13343 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-08-03T21:37:49+00:00