Actin-like and tubulin-like proteins in synaptic junctional complexes

Abstract
Synaptic junctional complexes (SJC) in rats, isolated by a procedure which preserves presynaptic dense projections (PDP) contain as their major component a polypeptide (P55) which comigrates with tubulin on sodium dodecyl sulfate-polyacrylamide gels and another major polypeptide (P45) which comigrates with muscle actin. The characterization of P55 and P45 was reported by 2-dimensional polyacrylamide gel electrophoresis and by peptide mapping of the radioiodinated polypeptides. P55 and P45 are homologous with tubulin and actin respectively, in terms of MW, protein charge and primary structure. Comparison of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns of SJC and postsynaptic densities (PSD) indicates that P55 and P45 are associated mainly with PDP but are found in the PSD.