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Structural analysis of monosaccharide recognition by rat liver mannose-binding protein
K K Ng1, K Drickamer, W I Weis
1Department of Structural Biology, Stanford University School of Medicine, California 94305, USA.
The Journal of Biological Chemistry
|January 12, 1996
Summary
Structural analysis of rat liver mannose-binding protein (MBP-C) reveals how it recognizes various sugars. The C-type carbohydrate-recognition domain (CRD) structure shows conserved calcium ion coordination for diverse monosaccharide binding.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Recognition
Background:
- Mannose-binding proteins (MBPs) are key in innate immunity and carbohydrate recognition.
- Understanding the structural basis of MBP carbohydrate binding is crucial for deciphering immune responses.
Purpose of the Study:
- To determine the three-dimensional structure of the C-type carbohydrate-recognition domain (CRD) of rat liver mannose-binding protein (MBP-C).
- To elucidate the structural mechanisms underlying MBP-C's recognition of various monosaccharides.
Main Methods:
- X-ray crystallography was used to determine the MBP-C CRD structure.
- Molecular replacement with rat serum MBP-A was employed for structure solution.
- Complexes with mannose, N-acetylglucosamine, fucose, and galactose were analyzed.
Main Results:
- The MBP-C CRD structure was refined to 1.7 A resolution.
- Despite similar folds, MBP-C and MBP-A dimeric structures differ significantly.
- Bound monosaccharides coordinate Ca2+ via vicinal hydroxyl groups, interacting with Ca2+ ligands.
- A conserved binding mode was observed for mannose, N-acetylglucosamine, fucose, and galactose.
- A second mannose binding site was identified at high sugar concentration.
Conclusions:
- The determined structures explain the broad monosaccharide recognition of MBPs.
- The findings suggest mechanisms for specificity differences between MBP-A and MBP-C.