Purification and characterization of a novel lectin from a freshwater cyanobacterium, Oscillatoria agardhii

In the survey of 14 species of laboratory-cultured cyanobacteria for hemagg lutinins, we newly detected the activity in two species, Oscillatoria agard hii; strain NIES-204, and Phormidium foveolarum, Strain NIES-503. From the extract of O. agardhii, which showed the highest activity with trypsin-trea ted erythrocytes of rabbit, a lectin was purified to homogeneity by the com bination of precipitation with (NH4)(2)SO4, pel filtration, hydrophobic chr omatography and reverse phase chromatography. The purified lectin, designat ed OAA, was a monomeric protein with an apparent molecular weight of 13 000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 16 000 on gel filtration. The amino acid composition was rich in glycine and acidic amino acids. The hemagglutination activity was inhibited by glycoproteins s uch as yeast mannan, but not by any of the monosaccharides tested. The acti vity was stable over a wide range of pH (4-11) and at a high temperature of 80 degrees C, and independent on the presence of divalent cations. The fea tures of OAA resembled those of many of lectins from marine macroalgae. The sequence of amino-terminal residues of OAA was determined as ALYNVENQWGGSS APWNEGG; which was highly homologous to those of lectins from macroalgae of the genus Eucheuma and that of a myxobacterium Myxococcus xanthus hemagglu tinin. (C) 2000 Elsevier Science Inc. All rights reserved.