Involvement of fodrin-binding proteins in the structure of the neuronal postsynaptic density and regulation by phosphorylation

Novel polypeptides with M_r values about 140,000 bind fodrin and spectrin and are enriched in the postsynaptic density (PSD) compared to other tissues or subcellular fractions. ¹²⁵I-fodrin binding to these polypeptides is competed for by unlabeled spectrin. These polypeptides are distinct from ankyrin and its proteolytic fragments and from band 4.1 which also bind fodrin. Phosphorylation of PSDs by the endogenous calmodulin-dependent protein kinase markedly reduces ¹²⁵I-fodrin binding to the transblotted preparation. Such an event may play a regulatory role in governing protein-protein interactions among elements of the PSD.