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Structure of Major Histocompatibility Complex – Antigen Processing and Presentation

by Peter Delves, PhD
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    Let’s look at the structure of the protein encoded by these genes. So for the α-chain of MHC Class I, the chain is folded into three different domains - an α1-domain, an α2-domain, and then sitting next to the membrane the α3-domain. It is just the α1 and the α2-domains of the α-chain of MHC Class I that is polymorphic. The β-chain as we’ve already mentioned, doesn’t vary at all from one individual to another in the MHC Class I molecules. It has a specific name, its called β2-microglobulin. And it doesn’t function in peptide binding but its function is to maintain the correct structural conformation of the MHC Class I molecule. And at the tip of this molecule are the two α-helices and the β-sheet floor that form the peptide binding groove where the peptide antigen sits. Here we can see, looking down onto the surface of the MHC Class I molecule, the two α-helices. Underlying those two α-helices is the β-sheet floor. And the peptide antigen sits between those two α-helices on the β-sheet floor as we can see in this diagram. The polymorphic residues in MHC Class I are indicated by these yellow squares in the diagram. And as you can see, the polymorphic residues occur both in the α-helices and on the β-sheet floor. And this is what determines which peptides will bind in the peptide binding group. So this is another representation of the structure of MHC Class I. You can see the non-variable β2-microglobulin and the three domain structure of the α-chain folded into the α1, α2 and α3-domains. And then the transmembrane region of the α-chain holding this molecule in the cell membrane. And at the tip we have the peptide binding groove with the peptide sitting between the two α-helices on the...

    About the Lecture

    The lecture Structure of Major Histocompatibility Complex – Antigen Processing and Presentation by Peter Delves, PhD is from the course Adaptive Immune System.


    Included Quiz Questions

    1. The α3 domain
    2. The α1 domain
    3. The α2 domain
    4. The β1 domain
    5. The β2 domain
    1. β2-microglobulin
    2. α1 domain
    3. α2 domain
    4. α chain
    5. α chain transmembrane sequence
    1. 8-9
    2. 15
    3. 200
    4. 4
    5. >3000
    1. ...must have amino acids that match an HLA type in order to bind, but the remaining amino acids can vary.
    2. ...dictate the sequence of the peptide that will bind to an HLA type.
    3. ...are the only factor that determine whether a peptide will bind to either an MHC Class I or an MHC Class II receptor.
    4. ...ensure that a peptide will attach to β2-microglobulin in order to be recognized by the immune system.
    5. ...are attached by MHC Class I molecules during the antigen recognition process.

    Author of lecture Structure of Major Histocompatibility Complex – Antigen Processing and Presentation

     Peter Delves, PhD

    Peter Delves, PhD


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