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PDBsum entry 1dn0
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Immune system
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PDB id
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1dn0
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Three-Dimensional structure of the FAB from a human igm cold agglutinin.
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Authors
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A.Cauerhff,
B.C.Braden,
J.G.Carvalho,
R.Aparicio,
I.Polikarpov,
J.Leoni,
F.A.Goldbaum.
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Ref.
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J Immunol, 2000,
165,
6422-6428.
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PubMed id
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Abstract
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Cold agglutinins (CAs) are IgM autoantibodies characterized by their ability to
agglutinate in vitro RBC at low temperatures. These autoantibodies cause
hemolytic anemia in patients with CA disease. Many diverse Ags are recognized by
CAs, most frequently those belonging to the I/i system. These are
oligosaccharides composed of repeated units of N:-acetyllactosamine, expressed
on RBC. The three-dimensional structure of the Fab of KAU, a human monoclonal
IgM CA with anti-I activity, was determined. The KAU combining site shows an
extended cavity and a neighboring pocket. Residues from the hypervariable loops
V(H)CDR3, V(L)CDR1, and V(L)CDR3 form the cavity, whereas the small pocket is
defined essentially by residues from the hypervariable loops V(H)CDR1 and
V(H)CDR2. This fact could explain the V(H)4-34 germline gene restriction among
CA. The KAU combining site topography is consistent with one that binds a
polysaccharide. The combining site overall dimensions are 15 A wide and 24 A
long. Conservation of key binding site residues among anti-I/i CAs indicates
that this is a common feature of this family of autoantibodies. We also describe
the first high resolution structure of the human IgM C(H)1:C(L) domain. The
structural analysis shows that the C(H)1-C(L) interface is mainly conserved
during the isotype switch process from IgM to IgG1.
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