A Monoclonal antibody 2: 6a recognizes a minor component protein of 38 k in the plain synaptic vesicleS

A monoclonal antibody 2.6A raised against the rat retinal membrane labeled most regions in the nervous system, where abundant synaptic terminals were present. An electron microscopic immunohistochemical study revealed that this antibody labeled plain synaptic vesicles on their cytoplasmic surface in the synapses. An immunoblot analysis demonstrated that the 2.6A antigen was a protein of which molecular weight was approximately 38 K. Since the properties of this antigen resembled those of the major synaptic vesicle protein, synaptophysin (SP), we attempted to study whether or not the 2.6A antigen was identical to SP. The synaptic vesicle proteins of about 38 K including SP were extracted from the SDS-PAGE gel. Dot blot analysis on these proteins revealed that SP was not stained with 2.6A but a minor protein slightly smaller than SP was. These results showed that the 2.6A antibody recognized a minor component protein of unknown property so far in the plain synaptic vesicles.