Slime Mold Lectins

This chapter describes the slime mold lectins. A lectin is a sugar-binding protein of non-immune origin that agglutinates cells or precipitates glycoconjugates. The assay with which the lectins are identified is the hemagglutination assay. The key to this assay is finding a species of erythrocyte or a particular treatment of the erythrocytes that renders them agglutinable and, hence useful as a sensitive assay reagent. Hapten inhibition with simple saccharides or glycoconjugates is used to define the specificity of the carbohydrate binding activity of the lectins. Lectins are the major components of soluble extracts of aggregation-competent slime mold cells. As components of the cytoskeleton, the slime mold lectins can function to regulate endocytosis, exocytosis, cell movement, cell shape, or the mobilities of cell surface components, any of which could be important for the formation of tight cellular aggregates during development. The lectin hypothesis for cell cohesion in the cellular slime molds has stimulated a search for lectins in other organisms as well as an investigation of their possible roles in mediating recognition phenomena.