because previous studies have shown that treatment of cells and cell membranes with pertussis toxin results in attenuation of the effects of hormones that inhibit adenylyl cyclase activity , and because this effect correlates with the adp-ribosylation of a mr approximately equal to 40,000 peptide , we believe that we have purified a guanine nucleotide- and mg2+-binding inhibitory regulatory component of adenylyl cyclases -- i.e. , the ni .
C0007634
cells
C0007603
cell membranes