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| | == Structural highlights == | | == Structural highlights == |
| | <table><tr><td colspan='2'>[[1pk6]] 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=1PK6 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1PK6 FirstGlance]. <br> | | <table><tr><td colspan='2'>[[1pk6]] 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=1PK6 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1PK6 FirstGlance]. <br> |
| - | </td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene></td></tr> | + | </td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.85Å</td></tr> |
| - | <tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat"><div style='overflow: auto; max-height: 3em;'>[[1gpz|1gpz]], [[1elv|1elv]], [[1nzi|1nzi]]</div></td></tr> | + | <tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</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=1pk6 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1pk6 OCA], [https://pdbe.org/1pk6 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1pk6 RCSB], [https://www.ebi.ac.uk/pdbsum/1pk6 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1pk6 ProSAT]</span></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=1pk6 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1pk6 OCA], [https://pdbe.org/1pk6 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1pk6 RCSB], [https://www.ebi.ac.uk/pdbsum/1pk6 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1pk6 ProSAT]</span></td></tr> |
| | </table> | | </table> |
| | == Disease == | | == Disease == |
| - | [[https://www.uniprot.org/uniprot/C1QA_HUMAN C1QA_HUMAN]] Defects in C1QA are a cause of complement component C1q deficiency (C1QD) [MIM:[https://omim.org/entry/613652 613652]]. A rare defect resulting in C1 deficiency and impaired activation of the complement classical pathway. C1 deficiency generally leads to severe immune complex disease with features of systemic lupus erythematosus and glomerulonephritis. [[https://www.uniprot.org/uniprot/C1QC_HUMAN C1QC_HUMAN]] Defects in C1QC are a cause of complement component C1q deficiency (C1QD) [MIM:[https://omim.org/entry/613652 613652]]. A rare defect resulting in C1 deficiency and impaired activation of the complement classical pathway. C1 deficiency generally leads to severe immune complex disease with features of systemic lupus erythematosus and glomerulonephritis.<ref>PMID:8630118</ref> [[https://www.uniprot.org/uniprot/C1QB_HUMAN C1QB_HUMAN]] Defects in C1QB are a cause of complement component C1q deficiency (C1QD) [MIM:[https://omim.org/entry/613652 613652]]. A rare defect resulting in C1 deficiency and impaired activation of the complement classical pathway. C1 deficiency generally leads to severe immune complex disease with features of systemic lupus erythematosus and glomerulonephritis.<ref>PMID:9476130</ref>
| + | [https://www.uniprot.org/uniprot/C1QA_HUMAN C1QA_HUMAN] Defects in C1QA are a cause of complement component C1q deficiency (C1QD) [MIM:[https://omim.org/entry/613652 613652]. A rare defect resulting in C1 deficiency and impaired activation of the complement classical pathway. C1 deficiency generally leads to severe immune complex disease with features of systemic lupus erythematosus and glomerulonephritis. |
| | == Function == | | == Function == |
| - | [[https://www.uniprot.org/uniprot/C1QA_HUMAN C1QA_HUMAN]] C1q associates with the proenzymes C1r and C1s to yield C1, the first component of the serum complement system. The collagen-like regions of C1q interact with the Ca(2+)-dependent C1r(2)C1s(2) proenzyme complex, and efficient activation of C1 takes place on interaction of the globular heads of C1q with the Fc regions of IgG or IgM antibody present in immune complexes. [[https://www.uniprot.org/uniprot/C1QC_HUMAN C1QC_HUMAN]] C1q associates with the proenzymes C1r and C1s to yield C1, the first component of the serum complement system. The collagen-like regions of C1q interact with the Ca(2+)-dependent C1r(2)C1s(2) proenzyme complex, and efficient activation of C1 takes place on interaction of the globular heads of C1q with the Fc regions of IgG or IgM antibody present in immune complexes. [[https://www.uniprot.org/uniprot/C1QB_HUMAN C1QB_HUMAN]] C1q associates with the proenzymes C1r and C1s to yield C1, the first component of the serum complement system. The collagen-like regions of C1q interact with the Ca(2+)-dependent C1r(2)C1s(2) proenzyme complex, and efficient activation of C1 takes place on interaction of the globular heads of C1q with the Fc regions of IgG or IgM antibody present in immune complexes.
| + | [https://www.uniprot.org/uniprot/C1QA_HUMAN C1QA_HUMAN] C1q associates with the proenzymes C1r and C1s to yield C1, the first component of the serum complement system. The collagen-like regions of C1q interact with the Ca(2+)-dependent C1r(2)C1s(2) proenzyme complex, and efficient activation of C1 takes place on interaction of the globular heads of C1q with the Fc regions of IgG or IgM antibody present in immune complexes. |
| | == Evolutionary Conservation == | | == Evolutionary Conservation == |
| | [[Image:Consurf_key_small.gif|200px|right]] | | [[Image:Consurf_key_small.gif|200px|right]] |
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| | [[Category: Homo sapiens]] | | [[Category: Homo sapiens]] |
| | [[Category: Large Structures]] | | [[Category: Large Structures]] |
| - | [[Category: Arlaud, G J]] | + | [[Category: Arlaud GJ]] |
| - | [[Category: Darnault, C]] | + | [[Category: Darnault C]] |
| - | [[Category: Fontecilla-Camps, J C]] | + | [[Category: Fontecilla-Camps JC]] |
| - | [[Category: Gaboriaud, C]] | + | [[Category: Gaboriaud C]] |
| - | [[Category: Gruez, A]] | + | [[Category: Gruez A]] |
| - | [[Category: Juanhuix, J]] | + | [[Category: Juanhuix J]] |
| - | [[Category: Lacroix, M]] | + | [[Category: Lacroix M]] |
| - | [[Category: Pignol, D]] | + | [[Category: Pignol D]] |
| - | [[Category: Verger, D]] | + | [[Category: Verger D]] |
| - | [[Category: C1q]]
| + | |
| - | [[Category: Complement system]]
| + | |
| - | [[Category: Igg]]
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| - | [[Category: Immune system]]
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| - | [[Category: Immunology]]
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| - | [[Category: Jellyroll]]
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| Structural highlights
Disease
C1QA_HUMAN Defects in C1QA are a cause of complement component C1q deficiency (C1QD) [MIM:613652. A rare defect resulting in C1 deficiency and impaired activation of the complement classical pathway. C1 deficiency generally leads to severe immune complex disease with features of systemic lupus erythematosus and glomerulonephritis.
Function
C1QA_HUMAN C1q associates with the proenzymes C1r and C1s to yield C1, the first component of the serum complement system. The collagen-like regions of C1q interact with the Ca(2+)-dependent C1r(2)C1s(2) proenzyme complex, and efficient activation of C1 takes place on interaction of the globular heads of C1q with the Fc regions of IgG or IgM antibody present in immune complexes.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
C1q is a versatile recognition protein that binds to an amazing variety of immune and non-immune ligands and triggers activation of the classical pathway of complement. The crystal structure of the C1q globular domain responsible for its recognition properties has now been solved and refined to 1.9 A of resolution. The structure reveals a compact, almost spherical heterotrimeric assembly held together mainly by non-polar interactions, with a Ca2+ ion bound at the top. The heterotrimeric assembly of the C1q globular domain appears to be a key factor of the versatile recognition properties of this protein. Plausible three-dimensional models of the C1q globular domain in complex with two of its physiological ligands, C-reactive protein and IgG, are proposed, highlighting two of the possible recognition modes of C1q. The C1q/human IgG1 model suggests a critical role for the hinge region of IgG and for the relative orientation of its Fab domain in C1q binding.
The crystal structure of the globular head of complement protein C1q provides a basis for its versatile recognition properties.,Gaboriaud C, Juanhuix J, Gruez A, Lacroix M, Darnault C, Pignol D, Verger D, Fontecilla-Camps JC, Arlaud GJ J Biol Chem. 2003 Nov 21;278(47):46974-82. Epub 2003 Sep 5. PMID:12960167[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Gaboriaud C, Juanhuix J, Gruez A, Lacroix M, Darnault C, Pignol D, Verger D, Fontecilla-Camps JC, Arlaud GJ. The crystal structure of the globular head of complement protein C1q provides a basis for its versatile recognition properties. J Biol Chem. 2003 Nov 21;278(47):46974-82. Epub 2003 Sep 5. PMID:12960167 doi:http://dx.doi.org/10.1074/jbc.M307764200
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