Mannose binding

Abstract: Tetrameric Galanthus nivalis agglutinin (50,000 Mr) belongs to a super-family of α-D-mannose-specific plant bulb lectins known to be potent inhibitors of retroviruses. The 2.3 A crystal structure of this lectin complexed with methyl α-D-mannose reveals a novel three-fold symmetric β-sheet polypeptide fold. Three antiparallel four-stranded β-sheets, each with a conserved mannose-binding site, are arranged as a 12-stranded β-barrel. The tetramer displays 222 symmetry. Pairs of monomers form stable dinners through C-terminal strand exchange. The so formed hybrid β-sheets are the sites for high affinity mannose binding in the dimer interface. Occupancy observed at corresponding sites in other β-sheets suggests a potential for twelve sites per tetramer.

Abstract: We have purified the human lymphocyte Fc receptor specific for IgE (Fc epsilon receptor) and its soluble form by using the anti-Fc epsilon receptor monoclonal antibody H107. Using an oligonucleotide probe corresponding to the partial amino acid sequence of the soluble Fc epsilon receptor related to IgE binding factor, we cloned, sequenced, and expressed a cDNA for the receptor. The Fc epsilon receptor has 321 amino acid residues with no NH2-terminal signal sequence. The receptor was separated into two domains by a putative 24-amino acid residue transmembrane region located near the NH2-terminal end. The Fc epsilon receptor showed a marked homology with animal lectins including human and rat asialoglycoprotein receptors, chicken hepatic lectin, and rat mannose binding proteins.