Lectin binding studies on the slime mold, Physarum polycephalum.

Abstract

ABSTRACT. Cell surface glycoconjugate receptors for wheat germ agglutinin, Ricinus communis agglutinin, concanavalin A and soybean agglutinin on two strains of myxoamoebae of Physarum polycephalum with fluorescein isothiocynate-labelled lectins were observed microscopically, but no receptors for Dolichos biflorus agglutinin, Ulex europeus agglutinin-I and Arachis hypogaea agglutinin were found. These results suggest that the myxoamoebae have cell surface glycoproteins with N-glycosidically linked hetero-saccharide chains, but not oligosaccharides with blood group A and H determinants. The number of lectin receptor sites and their affinity constants for lectins were obtained for the myxoamoebae and microplasmodia of P. polycephalum from binding assays with 125I-lectins. The densities of these lectin receptors and the magnitudes of the affinity constants were similar to those of mammalian cells. Neuraminidase treatment of the myxoamoebae and microplasmodia induced neither a decrease in WGA receptors nor an increase in RCA receptors. These results are strong evidence that sialyl residues are absent in glycoconjugates on the surface of the myxoamoebae and microplasmodia of P. polycephalum.