Abstract
Cholinergic synaptic vesicles purified from the electric organ of the marine ray, Discopyge ommata, contain 2 different size classes of GTP- binding proteins: one or more with an apparent molecular weight (MW) between 37 and 41 kDa, and 3 major and at least 2 minor proteins with MW between 20 and 29 kDa. These GTP-binding proteins were detectable using the alpha 32P-GTP overlay technique and covalent modification with bacterial toxins. The higher MW GTP-binding proteins are ADP- ribosylated by pertussis toxin and 2 of the lower MW GTP-binding proteins are sensitive to botulinum toxin.