Functional and structural characterization of multiple galectins from the skin mucus of conger eel, Conger myriaster

The complete amino acid sequence of an isogalectin, named congerin II, isol ated from the skin mucus of conger eel, was determined by sequencing of the protein and its peptides generated by enzymatic and chemical cleavages. Co ngerin II consisted of 135 amino acids residues containing an acetylated N- terminus. Congerin II was found to be only 46% homologous in sequence to co ngerin I which was previously determined (Muramoto K., Kamiya H., Biochem. Biophys. Acta, 1992;1116:129-136), suggesting that the galectins with diver se molecular properties are present in the skill mucus of conger eel. Howev er, it was confirmed by analysis of the secondary structures using circular dichroism that both congerins I and II shared similar folds characterized by beta structures. Congerins I and II showed different molecular propertie s such as thermostability, pH dependency for hemagglutinating activity and for binding specificity against the pyridylamino derivative of lactose. Con gerin I showed more strict recognition specificity for lactose than did con gerin II. Furthermore, the effects of chemical modification on congerins I and II were investigated in order to identify the type of amino acids invol ved in their different lectin activities. Modification of tyrosine and lysi ne residues did not affect the carbohydrate-binding activities of congerins . However, modification of tryptophan, arginine, histidine, glutamic acid a nd aspartic acid residues led to considerable loss of their activities, and a different mode of binding activity was observed between modified congeri ns I and II. These results suggest that multiple galectins from conger eel with the same scaffold have different biological functions and properties. (C) 1999 Elsevier Science Inc. All rights reserved.