Association between the first two immunoglobulin-like domains of the neural cell adhesion molecule N-CAM

The extracellular domain of N-CAM contains five immunoglobulin-like (Ig) an d two fibronectin type III-like domains and facilitates cell-cell binding t hrough multiple, weak interdomain interactions. NMR spectroscopy indicated that the two N-terminal Ig-like domains from chicken N-CAM (Ig I and Ig II) interact with millimolar affinity. Physico-chemical studies show that this interaction is significantly amplified when the domains are covalently lin ked, consistent with an antiparallel domain arrangement. The binding of the two individual domains and the dimerization of the concatenated protein we re essentially independent of salt, up to a concentration of 200 mM. The re sidues in Ig I involved in the interaction map to the BED strands of the be ta sandwich, and delineate a largely hydrophobic patch. (C) 1999 Federation of European Biochemical Societies.