You develop a new drug that inhibits the action of nsf. you test the drug for its ability to inhibit vesicle fusion in an in vitro assay containing purified vesicles, purified target membranes (with active rabs), cytosol, atp, and gtp. in your control, you can stimulate fusion by adding calcium to the mixture. assume the cytosol and nucleotides are in unlimited supply and that there are 3 moles of snare complex proteins and 1 mole of vesicles per round of stimulation. (more are added each round) you stimulated the system once, then repeatedly add fresh vesicles and re-stimulate. in the experiment, you are adding both atp and gtp. which of these is necessary?