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PDBsum entry 4cdh
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Immune system
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PDB id
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4cdh
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References listed in PDB file
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Key reference
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Title
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Structural basis for selective recognition of endogenous and microbial polysaccharides by macrophage receptor sign-R1.
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Authors
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N.Silva-Martín,
S.G.Bartual,
E.Ramírez-Aportela,
P.Chacón,
C.G.Park,
J.A.Hermoso.
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Ref.
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Structure, 2014,
22,
1595-1606.
[DOI no: ]
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PubMed id
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Abstract
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SIGN-R1 is a principal receptor for microbial polysaccharides uptake and is
responsible for C3 fixation via an unusual complement activation pathway on
splenic marginal zone macrophages. In these macrophages, SIGN-R1 is also
involved in anti-inflammatory activity of intravenous immunoglobulin by direct
interaction with sialylated Fcs. The high-resolution crystal structures of
SIGN-R1 carbohydrate recognition domain and its complexes with dextran sulfate
or sialic acid, and of the sialylated Fc antibody provide insights into
SIGN-R1’s selective recognition of a-2,6-sialylated glycoproteins.
Unexpectedly, an additional binding site has been found in the SIGNR1
carbohydrate recognition domain, structurally separate from the
calcium-dependent carbohydrate-binding site. This secondary binding site could
bind repetitive molecular patterns, as observed in microbial polysaccharides, in
a calcium-independent manner. These two binding sites may allow SIGNR1 to
simultaneously bind both immune glycoproteins and microbial polysaccharide
components, accommodating SIGN-R1’s ability to relate the recognition of
microbes to the activation of the classical complement pathway.
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