THE MAJOR VAULT PROTEIN (MVP100) IS CONTAINED IN CHOLINERGIC NERVE-TERMINALS OF ELECTRIC RAY ELECTRIC ORGAN

A protein of M(r) 100,000 (MVP100) is highly enriched in the electromo tor system of electric rays, Biochemical analysis indicates that MVP10 0 is contained in the cholinergic nerve terminals of Torpedo electric organ as part of a large cytosolic complex. On sucrose density gradien t centrifugation MVP100 comigrates with synaptic vesicles or synaptoso mes. It can be partially separated from synaptic vesicles by gel filtr ation or glycerol velocity gradient centrifugation. Within the complex MVP100 behaves like a hydrophobic protein and is protected against pr oteolytic attack. MVP100 can be immunodetected by are antibody against phosphotyrosine, and it becomes phosphorylated on incubation with [ga mma-P-32]ATP. By screening an electric ray electric lobe cDNA library the primary structure of MVP100 was analyzed MVP100 is highly homologo us to the major vault proteins of slime mold and rat and to the human lung resistance-related protein. Compared with non-neural tissues the expression of MVP100 is highest in brain and enriched in the electric lobe that contains the somata of the electromotor neurons. Immunoelect ron microscopic analysis reveals a close association of MVP100 and syn aptic vesicles in the nerve terminals of the electric organ.