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is not true...
1) Calnexin and Calreticulin are chaperones in the Cytosolic pathway
2) Class I MHC molecules are heterodimers
3) Class II MHC molecules are homodimers
4) Invariant chain helps dimerize alpha and beta chains of class II MHC molecules
5) Class II MHC molecules are involved in the endocytic pathway
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sorry...try again guys... don't need to know a lot of details, just read the choices carefully...
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"Like MHC class I molecules, class II molecules are also heterodimers, but in this case consist of two homologous peptides, an α and β chain, both of which are encoded in the MHC" - MHC Class 2 Structure -wikipedia
If the above is correct then 3 is the answer.
The Invariant chain blocks the MHC binding site preventing it from binding protein from the endogenous pathway. The Invariant chain is a trimer!
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u're right eljamoo... 3 is the answer!
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yeah it is obvious that 3 is the correct answer ! But I still can't understand choice 4. What is meant by helps dimerize alpha and beta chains ?
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helps them get together fexofenadine... stay attached to each other, until the processed peptide comes and binds...
wiki:
During synthesis, MHC class II is the result of dimerization of α and β chains, with the assistance of an invariant chain.[2] The invariant chain is a special polypeptide involved in the formation and deliverance of MHC class II protein.
wiki: The nascent MHC class II protein in the rough ER has its peptide-binding cleft blocked by the invariant chain (Ii; a trimer) to prevent it from binding cellular peptides or peptides from the endogenous pathway. The invariant chain also facilitates MHC class II's export from the ER in a vesicle. This fuses with a late endosome containing the endocytosed, degraded proteins. It is then broken down in stages, leaving only a small fragment called CLIP which still blocks the peptide binding cleft. An MHC class II-like structure, HLA-DM, removes CLIP and replaces it with a peptide from the endosome. The stable MHC class-II is then presented on the cell surface.
