two gtp-binding trimeric proteins ( referred to as alpha 41 beta gamma and alpha 39 beta gamma based on the kilodalton molecular weights of their alpha-subunits ) were purified from rat brain as the specific substrates of the adp-ribosylation reaction catalyzed by islet-activating protein , pertussis toxin , and resolved irreversibly into alpha- and beta gamma-subunits by incubation with guanosine 5'-o- ( thiotriphosphate ) ( gtp gamma s ) .
C0018353
gtp
C0079469
gtp gamma s