Characterization of the kinetics of neural cell adhesion molecule homophilic binding

Abstract

A solid‐phase assay has been developed for the investigation of the kinetics of neural cell adhesion molecule (NCAM) binding. Using this assay we can show that NCAM binds to itself in a time‐dependent and saturable manner. Binding constants (K _B values) of 6.9 × 10⁻⁸ M and 1.23 × 10⁻⁶ M, respectively, were obtained for adult and newborn rat NCAM homophilic binding. Binding is specifically inhibited by Fab′ fragments of polyclonal anti‐NCAM antibodies but is unaffected by heparin or chondroitin sulphate. This indicates that the NCAM homophilic binding site is separate from and independent of the heparin‐binding site and that a developmental modification, probably polysialation, gives rise to marked differences in the adhesive properties of NCAM.