Complex carbohydrates serve diverse functions in biological systems. One of their roles is to act as recognition markers on the surface of cells and on extracellular glycoproteins. These oligosaccharides are selectively recognized by endogenous sugar-binding proteins that are designated animal lectins. Recognition of endogenous and exogenous carbohydrates by animal lectins is an important aspect of cell-cell adhesion, serum glycoprotein turnover and antibody-independent innate immunity. Many animal lectins contain discrete, Ca2+-dependent carbohydrate-recognition domains (C-type CRDs) of approximately 130 amino acids. These modules share an underlying sequence motif, suggesting that they are folded in similar ways and that, although each binds to a unique spectrum of sugars, the underlying mechanism for sugar recognition by all of these domains is likely to be related. It is proposed to study certain key C-type CRDs which serve as models for the way in which all CRDs in this class function. The goals are: (1) To develop a detailed molecular description of how individual CRDs interact with monosaccharides. (2) To define the arrangement of multiple CRDs within animal lectins, in order to understand how the intact lectin molecules interact with multivalent oligosaccharides. (3) To determine the changes in CRDs that are responsible for their loss of ligand-binding activity at low pH, which allows release of ligands in endosomes following endocytosis. A combination of x-ray crystallography, site-directed mutagenesis, limited proteolysis, expression of protein fragments, spectroscopic analysis of protein-sugar interactions, nuclear magnetic resonance, and computational modeling will be employed.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM042628-06
Application #
2181537
Study Section
Physiological Chemistry Study Section (PC)
Project Start
1989-07-01
Project End
1995-06-30
Budget Start
1994-07-01
Budget End
1995-06-30
Support Year
6
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Columbia University (N.Y.)
Department
Physiology
Type
Schools of Medicine
DUNS #
064931884
City
New York
State
NY
Country
United States
Zip Code
10027
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Iobst, S T; Drickamer, K (1996) Selective sugar binding to the carbohydrate recognition domains of the rat hepatic and macrophage asialoglycoprotein receptors. J Biol Chem 271:6686-93
Ruiz, N I; Drickamer, K (1996) Differential ligand binding by two subunits of the rat liver asialoglycoprotein receptor. Glycobiology 6:551-9
Ng, K K; Drickamer, K; Weis, W I (1996) Structural analysis of monosaccharide recognition by rat liver mannose-binding protein. J Biol Chem 271:663-74
Weis, W I; Drickamer, K (1994) Trimeric structure of a C-type mannose-binding protein. Structure 2:1227-40
Iobst, S T; Drickamer, K (1994) Binding of sugar ligands to Ca(2+)-dependent animal lectins. II. Generation of high-affinity galactose binding by site-directed mutagenesis. J Biol Chem 269:15512-9
Iobst, S T; Wormald, M R; Weis, W I et al. (1994) Binding of sugar ligands to Ca(2+)-dependent animal lectins. I. Analysis of mannose binding by site-directed mutagenesis and NMR. J Biol Chem 269:15505-11
Taylor, M E (1993) Recognition of complex carbohydrates by the macrophage mannose receptor. Biochem Soc Trans 21:468-73
Verrey, F; Drickamer, K (1993) Determinants of oligomeric structure in the chicken liver glycoprotein receptor. Biochem J 292 ( Pt 1):149-55

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