Differential recognition of core and terminal portions of oligosaccharide ligands by carbohydrate-recognition domains of two mannose-binding proteins.
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.
Childs
R A
RA
Glycoconjugates Section, Clinical Research Centre, Harrow, Middlesex, United Kingdom.
Feizi
T
T
Yuen
C T
CT
Drickamer
K
K
Quesenberry
M S
MS
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D006023:Glycoproteins / Q000378:metabolism; D006031:Glycosylation; D008024:Ligands; D008358:Mannose / Q000378:metabolism*; D037241:Mannose-Binding Lectins; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism
D002352:Carrier Proteins; D006023:Glycoproteins; D008024:Ligands; D037241:Mannose-Binding Lectins; D009844:Oligosaccharides; D011994:Recombinant Proteins; D008358:Mannose