Biochemical evidence for the presence of NAP-22, a novel acidic calmodulin binding protein, in the synaptic vesicles of rat brain

Abstract NAP-22 is a neuronal tissue-enriched acidic protein which is expressed predominantly in rat brain. In the present study, we quantitated the amount of NAP-22 in a highly purified synaptic vesicle fraction. NAP-22 comprised 1.3±0.15% of the total protein in the fraction, and NAP-22 was located on the external surface of the synaptic vesicle membrane. The results suggest NAP-22 may be involved in the synaptic vesicle cycling.