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[[Image:1xed.jpg|left|200px]]<br /><applet load="1xed" size="350" color="white" frame="true" align="right" spinBox="true"
caption="1xed, resolution 1.90&Aring;" />
'''Crystal Structure of a Ligand-Binding Domain of the Human Polymeric Ig Receptor, pIgR'''<br />


==Overview==
==Crystal Structure of a Ligand-Binding Domain of the Human Polymeric Ig Receptor, pIgR==
The polymeric immunoglobulin receptor (pIgR) is a type I transmembrane, protein that delivers dimeric IgA (dIgA) and pentameric IgM to mucosal, secretions. Here, we report the 1.9 A resolution X-ray crystal structure, of the N-terminal domain of human pIgR, which binds dIgA in the absence of, other pIgR domains with an equilibrium dissociation constant of 300 nM., The structure of pIgR domain 1 reveals a folding topology similar to, immunoglobulin variable domains, but with differences in the counterparts, of the complementarity determining regions (CDRs), including a helical, turn in CDR1 and a CDR3 loop that points away from the other CDRs. The, unusual CDR3 loop position prevents dimerization analogous to the pairing, of antibody variable heavy and variable light domains. The pIgR domain 1, structure allows interpretation of previous mutagenesis results and, structure-based comparisons between pIgR and other IgA receptors.
<StructureSection load='1xed' size='340' side='right'caption='[[1xed]], [[Resolution|resolution]] 1.90&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1xed]] is a 6 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=1XED OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1XED 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]] 1.9&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=MG:MAGNESIUM+ION'>MG</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=1xed FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1xed OCA], [https://pdbe.org/1xed PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1xed RCSB], [https://www.ebi.ac.uk/pdbsum/1xed PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1xed ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/PIGR_HUMAN PIGR_HUMAN] This receptor binds polymeric IgA and IgM at the basolateral surface of epithelial cells. The complex is then transported across the cell to be secreted at the apical surface. During this process a cleavage occurs that separates the extracellular (known as the secretory component) from the transmembrane segment.
== 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/xe/1xed_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=1xed ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The polymeric immunoglobulin receptor (pIgR) is a type I transmembrane protein that delivers dimeric IgA (dIgA) and pentameric IgM to mucosal secretions. Here, we report the 1.9 A resolution X-ray crystal structure of the N-terminal domain of human pIgR, which binds dIgA in the absence of other pIgR domains with an equilibrium dissociation constant of 300 nM. The structure of pIgR domain 1 reveals a folding topology similar to immunoglobulin variable domains, but with differences in the counterparts of the complementarity determining regions (CDRs), including a helical turn in CDR1 and a CDR3 loop that points away from the other CDRs. The unusual CDR3 loop position prevents dimerization analogous to the pairing of antibody variable heavy and variable light domains. The pIgR domain 1 structure allows interpretation of previous mutagenesis results and structure-based comparisons between pIgR and other IgA receptors.


==Disease==
Crystal structure of a polymeric immunoglobulin binding fragment of the human polymeric immunoglobulin receptor.,Hamburger AE, West AP Jr, Bjorkman PJ Structure. 2004 Nov;12(11):1925-35. PMID:15530357<ref>PMID:15530357</ref>
Known disease associated with this structure: IgA nephropathy, susceptibility to OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=173880 173880]]


==About this Structure==
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
1XED is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=MG:'>MG</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XED OCA].
</div>
 
<div class="pdbe-citations 1xed" style="background-color:#fffaf0;"></div>
==Reference==
== References ==
Crystal structure of a polymeric immunoglobulin binding fragment of the human polymeric immunoglobulin receptor., Hamburger AE, West AP Jr, Bjorkman PJ, Structure. 2004 Nov;12(11):1925-35. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=15530357 15530357]
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Homo sapiens]]
[[Category: Single protein]]
[[Category: Large Structures]]
[[Category: Bjorkman, P.J.]]
[[Category: Bjorkman PJ]]
[[Category: Hamburger, A.E.]]
[[Category: Hamburger AE]]
[[Category: Jr., A.P.West.]]
[[Category: West Jr AP]]
[[Category: MG]]
[[Category: ig-like fold]]
 
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