HLA-DM
Encyclopedia
HLA-DM is an intracellular
Intracellular
Not to be confused with intercellular, meaning "between cells".In cell biology, molecular biology and related fields, the word intracellular means "inside the cell".It is used in contrast to extracellular...

 protein involved in peptide presentation by MHC class II
MHC class II
MHC Class II molecules are found only on a few specialized cell types, including macrophages, dendritic cells and B cells, all of which are professional antigen-presenting cells ....

. It is encoded by the genes and .

In the endosomes, HLA-DM functions by promoting the dissociation of the CLIP
CLIP (protein)
CLIP or Class II-associated invariant chain peptide is the part of the invariant chain that binds MHC class II groove and remains there until the MHC receptor is fully assembled...

 peptide (a place holder peptide) from MHC class II which allows endosomal peptides to bind. Possibly by its preferential binding of the open, peptide-less conformation of MHC class II, HLA-DM then catalyzes peptide exchange, favoring more stable peptide-MHC complexes (which are resistant to DM action). Thus, HLA-DM is thought to play an important role in "editing" the peptide repertoire.

HLA-DM is a protein involved in the immune system. It is a molecular chaperone that works in lysosomes and endosomes. HLA-DM plays a role in the proper loading of peptides and presentation of the peptides in macrophages, dendritic cells, B cells, and other antigen presenting cells. The protein is unable to bind peptides itself, so it interacts with major histocompatibility protein II (MHCII) to speed up the molecule’s binding and releasing of peptides. HLA-DM regulates the peptides that bind to MHCII and present the antigen on antigen presenting cells, therefore controlling which antigen(s) the body mounts and immune response to.

The genes for HLA-DM are located in the MHCII region of the human chromosome 6. The genes code for the alpha and beta chains that makeup the protein. HLA-DM consists of two polymers and three ligands: BETA-D-MANNOSE (BMA), CHLORIDE ION (CL), and 2-(ACETYLAMINO)-2-DEOXY-A-D-GLUCOPYRANOSE (NDG). The structure of HLA-DM was determined by x-ray diffraction at a resolution of 2.27 Å.

The Ramachandran Plot of HLA-DM can be seen here here.

External links

  • Overview at Davidson College
    Davidson College
    Davidson College is a private liberal arts college in Davidson, North Carolina. The college has graduated 23 Rhodes Scholars and is consistently ranked in the top ten liberal arts colleges in the country by U.S. News and World Report magazine, although it has recently dropped to 11th in U.S. News...

    (student generated)
  • http://www.pdb.org/pdb/explore/explore.do?structureId=2BC4 Protein Data Bank
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