MAJOR LECTIN OF ALLIGATOR LIVER IS SPECIFIC FOR MANNOSE L-FUCOSE

We surveyed the calcium-requiring (C-type) lectins in alligator liver. The major lectin purified by affinity chromatography was termed allig ator hepatic lectin (AHL) and was found to be specific for mannose/L-f ucose. AHL contained approximately equal amounts of 21- and 23-kDa ban ds upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Bin ding characteristics of AHL were similar to those of hepatic lectins o f other classes in that 1) only terminal monosaccharide was recognized , and 2) the affinity increased exponentially when neoglycoproteins co ntaining increasing numbers of mannose or L-fucose were used as ligand . However, unlike mammalian and chicken hepatic lectins, which exist a s hexamers in Triton-containing solutions, AHL was present mainly as m onomers, although small amounts of dimer and higher oligomers were pre sent in equilibrium. Mannose binding proteins and mannose-specific lec tins of macrophages bind N-acetylmannosamine, glucose, and N-acetylglu cosamine in addition to mannose, indicating that the nature and orient ation of the C-2 substituent are not important to these lectins. In co ntrast, AHL shows a strict requirement for the presence of an axial hy droxyl group at the C-2 position (i.e. mannose).