View source for 1jk8


==Crystal structure of a human insulin peptide-HLA-DQ8 complex==
<StructureSection load='1jk8' size='340' side='right'caption='[[1jk8]], [[Resolution|resolution]] 2.40&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1jk8]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1JK8 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1JK8 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.4&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1jk8 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1jk8 OCA], [https://pdbe.org/1jk8 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1jk8 RCSB], [https://www.ebi.ac.uk/pdbsum/1jk8 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1jk8 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/DQA1_HUMAN DQA1_HUMAN] Binds peptides derived from antigens that access the endocytic route of antigen presenting cells (APC) and presents them on the cell surface for recognition by the CD4 T-cells. The peptide binding cleft accommodates peptides of 10-30 residues. The peptides presented by MHC class II molecules are generated mostly by degradation of proteins that access the endocytic route, where they are processed by lysosomal proteases and other hydrolases. Exogenous antigens that have been endocytosed by the APC are thus readily available for presentation via MHC II molecules, and for this reason this antigen presentation pathway is usually referred to as exogenous. As membrane proteins on their way to degradation in lysosomes as part of their normal turn-over are also contained in the endosomal/lysosomal compartments, exogenous antigens must compete with those derived from endogenous components. Autophagy is also a source of endogenous peptides, autophagosomes constitutively fuse with MHC class II loading compartments. In addition to APCs, other cells of the gastrointestinal tract, such as epithelial cells, express MHC class II molecules and CD74 and act as APCs, which is an unusual trait of the GI tract. To produce a MHC class II molecule that presents an antigen, three MHC class II molecules (heterodimers of an alpha and a beta chain) associate with a CD74 trimer in the ER to form a heterononamer. Soon after the entry of this complex into the endosomal/lysosomal system where antigen processing occurs, CD74 undergoes a sequential degradation by various proteases, including CTSS and CTSL, leaving a small fragment termed CLIP (class-II-associated invariant chain peptide). The removal of CLIP is facilitated by HLA-DM via direct binding to the alpha-beta-CLIP complex so that CLIP is released. HLA-DM stabilizes MHC class II molecules until primary high affinity antigenic peptides are bound. The MHC II molecule bound to a peptide is then transported to the cell membrane surface. In B-cells, the interaction between HLA-DM and MHC class II molecules is regulated by HLA-DO. Primary dendritic cells (DCs) also to express HLA-DO. Lysosomal miroenvironment has been implicated in the regulation of antigen loading into MHC II molecules, increased acidification produces increased proteolysis and efficient peptide loading.
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/jk/1jk8_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview03.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1jk8 ConSurf].
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== Publication Abstract from PubMed ==
The class II major histocompatibility complex (MHC) glycoproteins HLA-DQ8 and HLA-DQ2 in humans and I-A(g7) in nonobese diabetic (NOD) mice are the major risk factors for increased susceptibility to type 1 diabetes. Using X-ray crystallography, we have determined the three-dimensional structure of DQ8 complexed with an immunodominant peptide from insulin. The similarity of the DQ8, DQ2 and I-A(g7) peptide-binding pockets suggests that diabetes is caused by the same antigen-presentation event(s) in humans and NOD mice. Correlating type 1 diabetes epidemiology and MHC sequences with the DQ8 structure suggests that other structural features of the P9 pocket in addition to position 57 contribute to susceptibility to type 1 diabetes.

Structure of a human insulin peptide-HLA-DQ8 complex and susceptibility to type 1 diabetes.,Lee KH, Wucherpfennig KW, Wiley DC Nat Immunol. 2001 Jun;2(6):501-7. PMID:11376336<ref>PMID:11376336</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Lee KH]]
[[Category: Wiley DC]]
[[Category: Wucherpfennig KW]]