Thesis

The application of plant lectins to specific questions concerning the nature of neoplastic and embryonic cell surface receptors

Lectins are carbohydrate binding proteins considered to be useful probes in the study of cell surface glycoproteins. Using microfluorometry, treatment of dissociated sea urchin embryo cells with fluorescein isothiocyanate-concanavalin A lectin showed differences in the topographical distribution of cell surface Con A receptor molecules in various embryonic stages. Capped and clustered distribution of receptor sites (indicating receptor mobility) appears in 95% of early dissociated embryo cells, but as development proceeds, certain populations of cells appear exhibiting no lateral mobility of surface receptor sites. The results suggest a correlation between cell behavior and surface lectin receptor site mobility. Purification of teratoma cell adhesion factor was accomplished by affinity chromatography with Ricinus communis lectin bound covalently to agarose beads. Aggregation promoting activity of this factor was recovered in a single peak when eluted with a D-galactose gradient, and SDS polyacrylamide gel electrophoresis showed a single band when stained for protein. Plant lectins are shown here to be of value in cell surface mapping and chemical purification of carbohydrate-containing molecules.

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