BEYOND PLANT LECTIN HISTOCHEMISTRY - PREPARATION AND APPLICATION OF MARKERS TO VISUALIZE THE CELLULAR-CAPACITY FOR PROTEIN-CARBOHYDRATE RECOGNITION

Oligosaccharides can store biological information. In this respect, th eir capacity even outmatches that of oligo- and polymeric structures o f nucleotides and amino acids, Protein-carbohydrate interactions are t hus considered to be involved in the regulation of diverse cellular ac tivities. Over decades, plant lectins have proven valuable for assessi ng structural aspects of the enormous variety of carbohydrate epitopes and for monitoring spatially and/or temporally restricted patterns of expression. If the presence of these epitopes and the alterations in their occurrence bear physiological relevance, one reasonable possibil ity is that the visualized saccharides serve as ligands in an operativ e protein-carbohydrate recognition system. To support the validity of this hypothesis, receptor sites for a sugar compound must be localized . Carrier-immobilized carbohydrates (neoglycocon-jugates) are adequate for this purpose. Chemical synthesis gains access to such probes. In the first stage, the presence of binding sites such as lectins in the tissue is ascertained. The next step toward proving the outlined hypot hesis is the application of the first localized then purified endogeno us receptors as glycohistochemical markers. It is essential to point o ut that the fine specificities of plant and animal lectins can differ, although they share an identical monosaccharide specificity. Thus, ne oglycocon-jugates for localizing sugar ligand-binding proteins and end ogenous lectins to detect suitable binding partners are promising prob es to enhance our knowledge about the capacities of cells to be engage d in protein-carbohydrate recognition in situ.