XB-IMG-148722
Xenbase Image ID: 148722
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Figure 4. Structure of the main domain of malectin and of the malectin–nigerose complex. (A) Ensemble of the 10 lowest energy structures
(out of 100 calculated) after water refinement. The four loops (L1–L4), which could only be assigned in the presence of a carbohydrate ligand,
are highlighted in green: L1, G62-G68; L2, T86-N90; L3, E114-A118; and L4, Y185-N187. (B) Ribbon representation of malectin. Secondary
structure elements are colored in red and blue for -helices (1–3) and -strands (1–12), respectively. (C) Ensemble of the 10 lowest
energy structures of the malectin–nigerose complex. Only the ligand-binding pocket is shown. The four aromatic residues and D186
mediating the interaction are relatively well defined. Yellow, Y89; cyan, Y67; magenta, Y116; blue, F117; and brown, D186. Nigerose is
presented in green (D). Detailed view of the malectin–nigerose interaction. Nigerose is sandwiched by Y67, Y89, Y116, and F117. The
nonreducing and reducing residues of nigerose are labeled Glc-A and Glc-B, respectively. Oxygen atoms of the carbohydrate are highlighted
as red spheres. The orange arrow points to the oxygen atom of the C-2 hydroxyl group of Glc-A, where the outermost glucose residue of
Glc3-N-glycan would be attached. The magenta arrow highlights the oxygen atom of the C-1 hydroxyl group of Glc-B (-form), where the
polymannose part of the Glc2-N-glycan would be continued. The oxygen atom of the equatorial C-2 hydroxyl group of Glc-B is marked by
the yellow arrow. If at the Glc-B position there was a mannose residue, as in Glc1-N-glycan, the stacking interaction would be hindered as
there would be an axial hydroxyl group pointing toward Y116 and F117. (E) Schematic drawing of the Glc3-Man9-N-glycan. Glucose is
depicted as green circles, mannose as yellow squares, and GlcNAc as blue circles. Image published in: Schallus T et al. (2008) Copyright © 2008. Image reproduced with permission of the Publisher, American Society for Cell Biology (ASCB). This is an Open Access article. Larger Image Printer Friendly View |