Activation and attenuation of adenylate cyclase. The role of GTP-binding proteins as macromolecular messengers in receptor–cyclase coupling

Mechanism of glucagon activation of adenylate cyclase in the presence of Mn2+

“…This mechanism bears analogy with those proposed by others for P-agonist [12] and neurohypophyseal hormone [ 171 activation of adenylate cyclase. Such a mechanism allows for multiple catalytic units to be activated by a single occupied receptor.…”

Bimodal regulation of adenylate cyclase

“…A number of excellent reviews of this area have appeared [1][2][3]. As a prelude to a discussion of inhibition of adenylate cyclase it seems appropriate to present a brief perspective on stimulation of adenylate cyclase.…”

“…These and allied findings have led to the development of a general hypothesis, which proposes that hormone binding to receptors leads to the release of previously bound GDP (an ineffective stimulator), which allows occupancy by GTP and thus attainment of a more active R s • N s • C complex. On hydrolysis of GTP to GDP, the complex reverts to an inactive form, which coincides with the release of hormone [1][2][3].…”

The differential detergent solubilization of adenylate cyclase and polypeptides ADP‐ribosylated with cholera toxin suggests an excess of G/F protein relative to adenylate cyclase in rat pancreatic plasma membranes

“…Specificity of cholera toxin-dependent labelling and solubilization with G 3707 of ADP-ribosylated polypeptides of rat pancreatic plasma membranes. (A) Plasma membranes from rat pancreas [1,2] or human erythrocytes [3,4] were labelled in the absence [1,3] or presence [2,4] of 20 ug cholera toxin/ml, as in section 2. The medium contained the purified cytosolic factor and was buffered with 50 mM sodium phosphate (pH 7.4).…”