CHARACTERIZATION OF A NOVEL PYRUVYLATED CARBOHYDRATE UNIT IMPLICATED IN THE CELL-AGGREGATION OF THE MARINE SPONGE MICROCIONA-PROLIFERA

The species-specific Ca2+-dependent reaggregation of dissociated cells of the marine sponge Microciona prolifera is mediated by a large extr acellular adhesion proteoglycan. The glycans of this molecule are invo lved in the interactions of the proteoglycan with itself and with the sponge cells. Monoclonal antibodies against the glycans block the aggr egation of sponge cells (Misevic, G. N., Finne, J., and Burger, M. M. (1987) J. Biol. Chem. 262, 5870-5877). Proteoglycan oligosaccharides w ere prepared by partial acid hydrolysis of the isolated glycans, and t heir reactivity with the monoclonal antibodies was monitored after lin kage to phospholipid and immunostaining of thin layer chromatograms. O ne major antibody-reactive oligosaccharide was detected and purified b y ion-exchange chromatography and high performance liquid chromatograp hy. H-1 NMR spectroscopy, fast atom bombardment-mass spectrometry, met hylation analysis, and sequential chemical and enzymatic degradation s tudies indicated the structure [GRAPHICS] for the oligosaCcharide. The depyruvylated derivative of the oligosaccharide did not react with th e aggregation-blocking antibody, which indicates that the pyruvate ace tal is an essential part of the epitope.