What is the nature of peptide binding cleft in MHC II molecule?

What is the nature of peptide binding cleft in MHC II molecule?

The α1 and α2 domains fold together to form a cleft that represents the peptide-binding site. MHC class II molecules are heterodimers composed of two noncovalently joined transmembrane glycoproteins, α and β. Each chain has two domains. The α1 and β1 domains together form the peptide-binding cleft.

What is a peptide binding cleft?

The peptide binds in a cleft formed by a platform composed of eight b sheets and topped by two a-helical domains. The N-and C-termini are indicated at each end of the peptide. This combination opens the ends of the groove, allowing much longer peptides to bind to MHC class II molecules. …

What does MHC II bind to?

Thus; a) MHC class II molecule can bind to full-length protein antigens, b) just like peptide binding, DM enhances binding of full-length protein to DR1, and c) binding of protein to DR1 occurs through the peptide binding groove of DR1 rather than other possible sites.

Where do MHC class II molecules bind peptides?

MHC class II molecules bind the peptides generated in endosomes and the complexes are then exocytosed to the cell surface for presentation to CD4 T cells. Endogenous proteins and peptides may also bind MHC class II molecules following transport into the endosomal pathway.

Where are MHC class II molecules found?

MHC II is found only on macrophages, dendritic cells, and B cells.

Where do MHC II molecules get loaded with antigen peptides?

Loading of a MHC class II molecule occurs by phagocytosis; extracellular proteins are endocytosed, digested in lysosomes, and the resulting epitopic peptide fragments are loaded onto MHC class II molecules prior to their migration to the cell surface.

Where are class II MHC molecules found?

What is the source of peptides presented on MHC class I molecules and MHC class II molecules?

MHC I molecules present peptides from a cell’s expressed genes and thereby allow the immune system to monitor the proteins synthesized in a cell. The peptide transporter TAP allows peptides with these small modifications to enter the ER and some of these can bind to MHC I molecules for presentation to CD8+ T cells.

Is the MHC class II molecule the same peptide?

The recycled peptide–MHC class II complexes may contain the same peptide or newly acquired peptides loaded into the MHC class II molecule during recycling through the endosomes ( Machy et al., 1990 ).

How is the cleft of a peptide molecule formed?

The peptide-binding cleft of each molecule is formed by the α 1 and α 2 domains in the case of class I, whereas the α 1 and β 1 domains form this structure in class II molecules. S = disulfide bonds. Sources of the peptide antigens presented by class I and class II molecules are quite distinct.

Where are MHC class 2 transactivators found in the body?

They are expressed on the epithelial cells in the thymus and on APCs in the periphery. MHC class II expression is closely regulated in APCs by CIITA, which is the MHC class II transactivator.

What happens when MHC class II molecules are deficient?

Deficient MHC class II molecules are unable to present antigens to T cells and properly activate T cells. T cells are then unable to proliferate, and secrete cytokines which normally participate in the immune response.