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PDBsum entry 2ggu
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Sugar binding protein
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PDB id
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2ggu
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References listed in PDB file
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Key reference
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Title
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Contributions of phenylalanine 335 to ligand recognition by human surfactant protein d: ring interactions with sp-D ligands.
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Authors
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E.Crouch,
B.Mcdonald,
K.Smith,
T.Cafarella,
B.Seaton,
J.Head.
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Ref.
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J Biol Chem, 2006,
281,
18008-18014.
[DOI no: ]
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PubMed id
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Abstract
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Surfactant protein D (SP-D) is an innate immune effector that contributes to
antimicrobial host defense and immune regulation. Interactions of SP-D with
microorganisms and organic antigens involve binding of glycoconjugates to the
C-type lectin carbohydrate recognition domain (CRD). A trimeric fusion protein
encoding the human neck+CRD bound to the aromatic glycoside
p-nitrophenyl-alpha-D-maltoside with nearly a log-fold higher affinity than
maltose, the prototypical competitor. Maltotriose, which has the same linkage
pattern as the maltoside, bound with intermediate affinity. Site-directed
substitution of leucine for phenylalanine 335 (Phe-335) decreased affinities for
the maltoside and maltotriose without significantly altering the affinity for
maltose or glucose, and substitution of tyrosine or tryptophan for leucine
restored preferential binding to maltotriose and the maltoside. A mutant with
alanine at this position failed to bind to mannan or maltose-substituted solid
supports. Crystallographic analysis of the human neck+CRD complexed with
maltotriose or p-nitrophenyl-maltoside showed stacking of the terminal glucose
or nitrophenyl ring with the aromatic ring of Phe-335. Our studies indicate that
Phe-335, which is evolutionarily conserved in all known SP-Ds, plays important,
if not critical, roles in SP-D function.
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Figure 5.
FIGURE 5. Crystal structure of trimeric NCRD bound to
maltotriose. Ribbon representation of protein viewed
perpendicular to axis of neck domain, each subunit colored
differently. Maltotriose is shown as a ball-and-stick model and
calcium ions as green spheres. Maltotriose is bound in the same
orientation in each subunit. However, the interaction of the
trisaccharide with calcium ion 1 and the binding surface is most
clearly shown in the cyan subunit at left.
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Figure 8.
FIGURE 8. Superimposition of maltose and maltotriose bound
to the SP-D CRD. The protein model shows the maltotriose
complex. Maltose is shown as a green stick model (with rings
labeled G1–2 in green) and maltotriose as a magenta stick
model (with rings labeled G1–3 in magenta). The maltose was
aligned by least squares superimposition of residues in this
region using the structure of Protein Data Bank accession number
1PWB. Some of the hydrogen bonds between protein and maltotriose
are shown by green dashed lines.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2006,
281,
18008-18014)
copyright 2006.
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