Isolation and partial characterization of haemagglutinins from plasmodia of Physarum polycephalum

The soluble haemagglutinins produced by plasmodia of Physarum polycephalum were purified by chromatographic methods and resolved into haemagglutinins I and II. On SDS-PAGE, purified haemagglutinins I and II each gave a single band with an apparent molecular mass of 6 and 11 kDa, respectively. The results of gel-filtration chromatography suggested that both haemagglutinins were dimers of the respective subunits under non-denaturing conditions. Rabbit erythrocytes were preferentially agglutinated by both haemagglutinins. The human type A, B and O erythrocytes were agglutinated by haemagglutinin II to an equal degree but were not agglutinated by haemagglutinin I. Simple sugars failed to inhibit the activities of both haemagglutinins. The activities, however, were effectively inhibited by the addition of thyroglobulin. Other glycoproteins such as fetuin, orsomucoid and transferrin inhibited the activity of haemagglutinin I but not that of haemagglutinin II. These haemagglutinins were detected in a slime fraction obtained from the culture media of starved plasmodia, suggesting that they are released to the outside of the plasmalemma to become associated with the slime layer on the plasmodial surface.