Lectin binding studies on the slime mold, Physarum polycephalum.

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Abstract
Cell surface glycoconjugate receptors for wheat germ agglutinin, Ricinus communis agglutinin, concanavalin A and soybean agglutinin on 2 strains of myxoamoebae of P. polycephalum with fluorescein isothiocynate-labeled lectins were observed microscopically, but no receptors for Dolichos biflorus agglutinin, Ulex europaeus agglutinin-I and Arachis hypogaea agglutinin were found. Evidently, the myxoamoebae have cell surface glycoproteins with N-glycosidically linked heterosaccharide 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 [wheat germ agglutinin] receptors nor an increase in RCA [Ricinus communis agglutinin] receptors. Sialyl residues could be absent in glycoconjugates on the surface of the myxoamoebae and microplasmodia of P. polycephalum. These lectins may function in cellular aggregation.