Differential recognition of core and terminal portions of oligosaccharide ligands by carbohydrate-recognition domains of two mannose-binding proteins

• Published in: The Journal of biological chemistry 1990-12, Vol.265 (34), p.20770-20777
• Main Authors: Childs, R A, Feizi, T, Yuen, C T, Drickamer, K, Quesenberry, M S
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Base Sequence; Binding and carrier proteins; Binding Sites; Binding, Competitive; Biological and medical sciences; Carbohydrate Conformation; Carbohydrate Sequence; Carrier Proteins - genetics; Carrier Proteins - metabolism; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Glycoproteins - metabolism; Glycosylation; Ligands; liver; Mannose - metabolism; Mannose-Binding Lectins; Molecular Sequence Data; oligosaccharides; Oligosaccharides - metabolism; Proteins; Rats; Recombinant Proteins - metabolism; serum
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)45282-3

Two different mannose-binding proteins (MBP-A and MBP-C), which show 56% sequence identity, are present in rat serum and liver. It has previously been shown that MBP-A binds to a range of monosaccharide-bovine serum albumin conjugates, and that, among oligosaccharide ligands tested, preferential binding is to terminal nonreducing N-acetylglucosamine residues of complex type N-linked oligosaccharides. In order to compare the binding specificity of MBP-C, an expression system has been developed for production of a fragment of this protein which contains the COOH-terminal carbohydrate-recognition domain. After radioiodination, the domain has been used to probe natural glycoproteins, neoglycoproteins, and neoglycolipids. Like MBP-A, MBP-C binds several different monosaccharides conjugated to bovine serum albumin, including mannose, fucose, and N-acetylglucosamine, although binding to the last of these is relatively weaker than observed for MBP-A. The results of binding to natural glycoproteins and to neoglycolipids containing oligosaccharides derived from these proteins are most compatible with the interpretation that MBP-C interacts primarily with the trimannosyl core of complex N-linked oligosaccharides, with additional ligands being terminal fucose and perhaps also peripheral mannose residues of high mannose type oligosaccharides. This binding specificity is thus quite distinct from that of MBP-A. The presence of multiple MBPs with distinct binding specificities in preparations derived from serum and liver explains conflicting conclusions which have been reached about carbohydrate recognition by these proteins.