PURIFICATION AND CHARACTERIZATION OF MICROCYSTIS-AERUGINOSA (FRESH-WATER CYANOBACTERIUM) LECTIN

Microcystis aeruginosa, strain M228, a laboratory culture of freshwate r cyanobacterium, showed hemagglutinating activity against rabbit, hor se and human ABO erthrocytes. Crossed absorption tests revealed the pr esence of a single type of lectin in the extract of M228 strain cells. The lectin, termed MAL, was purified in combination with the affinity chromatography on acid-treated agarose gel and the gel permeation chr omatography in an electrophoretically pure form. MAL was a glycoprotei n containing 7.8% neutral sugars and was composed of a single polypept ide having a molecular weight of 57 kDa. Isoelectric point was estimat ed to be pH 6.4. Hemagglutinating activity of the lectin was inhibited effectively by N-acetyl-D-galactosamine and by glycoproteins. D-galac tose and lactose also showed moderate inhibitory activity. The destruc tion of the hemagglutinating activity by a 2-mercaptoethanol treatment suggests the presence of intra-chain disulfide bond(s) essential for the activity in the molecule. The sequence of the amino-terminal regio n of MAL was determined as Val-Lys-Ala-Ser-Lys-Val-Ser-Thr-Ser-Gln-Ala -Gly-S er-Lys-Glu-Lys-Lys-Ala. (C) 1998 Elsevier Science Inc. All righ ts reserved.