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Figure 4.
Fig. 4. A phenylalanine prevents binding of the inner
trimannosyl core of N-linked oligosaccharides. The DC-SIGNR CRD
is shown in cyan, with the Phe^325 side chain in a
ball-and-stick representation. In yellow-green, the outer
branched trimannose structure of Man[9] was superimposed on the
trimannose structure seen in the DC-SIGNR crystals. For clarity,
only the  1-6 branch
is shown. In magenta, the mannose residue of a model of the
internal Man  1-4GlcNAc
1-4GlcNAc
moiety of N-linked oligosaccharides was superimposed on the
central (reducing) mannose of the trimannose structure. The
model was made by setting the torsion angles of the glycosidic
linkages to their average values found in an oligosaccharide
structure database (13), with adjustments in the torsion angles
to overlay the branched trimannose structure precisely. The
clash of the first GlcNAc with Phe^325 is evident. In both the
positions of the 1-3 and
1-6 linked
mannose residues linked to the central mannose of the trimannose
structure are indicated in the black text.
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