title: The species-specific cell-binding site of the aggregation factor from the sponge Microciona prolifera is a highly repetitive novel glycan containing glucuronic acid, fucose, and mannose.
abstract: Species-specific adhesion of dissociated cells from the marine sponge Microciona prolifera is mediated by a Mr = 2 x 10(7) proteoglycan-like aggregation factor (MAF) via two highly polyvalent functional domains, a cell-binding and a self-interaction domain. Glycopeptide N-glycosidase F release of a major glycan of Mr = 6.3 gamma 10(3) (G-6) from the MAF protein core resulted in the loss of cell binding activity, indicating a role of this polysaccharide molecule in MAF-cell association. The G-6 glycan was isolated and purified after complete Pronase digestion of MAF using gel electrophoresis, gel filtration, and ion exchange chromatography. Quantification of the amount of carbohydrate recovered in G-6 showed that one MAF molecule has about 950 repeats of this glycan. In its monomeric state G-6 did not display any measurable binding to cells (K alpha less than or equal to 10(3) M-1). Intermolecular cross-linking of the G-6 glycan with glutaraldehyde resulted, however, in the concomitant recovery of polyvalency (about 2200 repeats of G-6 per polymer of Mr greater than or equal to 1.5 x 10(7) and species-specific high cell binding affinity (K alpha = 1.6 x 10(9) M-1) but not of the MAF-MAF self-interaction activity. Thus, the G-6 glycan is the multiple low affinity cell-binding site involved in cell-cell recognition and adhesion of sponge cells. The G-6 glycan has 7 glucuronic acids, 3 fucoses, 2 mannoses, 5 galactoses, 14 N-acetylglucosamines, 2 sulfates, and 1 asparagine. Such a unique chemical composition indicates a new type of structure which includes features of glycosaminolycans and N-linked polysaccharides.
authors.affiliation: Department of Research, University Hospital of Basel, Switzerland.
authors.forename: G N
authors.initials: GN
authors.lastname: Misevic
authors.forename: M M
authors.initials: MM
authors.lastname: Burger
mesh_terms: D000818:Animals; D002241:Carbohydrates / Q000032:analysis*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules; D002449:Cell Aggregation; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D005643:Fucose / Q000032:analysis; D005965:Glucuronates / Q000032:analysis; D020723:Glucuronic Acid; D006020:Glycopeptides / Q000302:isolation & purification; D008358:Mannose / Q000032:analysis; D008970:Molecular Weight; D011161:Porifera / Q000502:physiology*; D011506:Proteins / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D002241:Carbohydrates; D015815:Cell Adhesion Molecules; D005965:Glucuronates; D006020:Glycopeptides; D011506:Proteins; C013065:cell aggregation factors; D005643:Fucose; D020723:Glucuronic Acid; D008358:Mannose