The chick neural retina N-acetylgalactosaminyltransferase (gal NAc transferase) is localized at the cell surface and catalyzed the incorporation of N-acetylgalactosamine to the terminal position of O-linked oligosaccharide chains in a phosphodiester linkage. The enzyme is stably associated with the neural calcium dependent cell-cell adhesion molecule NcalCAM which is a primary acceptor for the enzymatic transfer of N- acetygalactosamine. The intimate association of the enzyme with NcalCAM, a correlation between the competence of cells to form calcium dependent adhesions and the presence of the transferase complex at the cell surface and finally, developmental changes in the distribution of the enzyme in retina suggest to us that the enzyme and/or the complex are involved in morphogenesis. We will analyze the structural organization of the transferase complex using the powerful combination of electron microscopy techniques and monoclonal antibodies. We will also explore the role of the enzyme complex in development using several different assay systems with antibodies and lastly, we will examine the possibility that similar enzyme/calCAM complexes exist in other tissues.
