Regulation of Adenylate Cyclase Activity by a GTP-Binding Peptida in Rat Liver.

A cytosolic peptide · GTP complex which stimulates iota-isoproterenol-responsive腺苷cyclase activity was identified in the rat liver。肽成分被纯化并表征，以调节其与GTP的相互作用，在腺苷的调节中。肽在1 mM NaHCO_3的Sephadex G-25柱上分离为复合形式，在200 mM醋酸铵中溶解为复合形式，在1 mM NaHCO_3上溶解为与Mr-3，000分离形式。纯化的肽单独显示了一种经标记的非经标记的刺激效应，但它的重新关联形式与GTP清楚地增强了GTP对酶活性的效应。使用iota的同位素竞争曲线-[^3 H]二氢戊醇（DHA）是由GTP （16.5-折叠移位）的肽相关附加物转移到较低的亲和力，同时GTP （1 mu M）的相同集中或单独的肽有轻微或无影响（1.5-或0.9-折叠，适当地）。Furthermore，肽增强了GTP效应在对碘-异氟醚的反应中的反应，但不包括在葡萄糖、前列腺素E_1和氟醚中。These results suggest that the peptide component of the cytosolic activator potentiates the effect of GTP on the agonist-beta-adrenergic receptor-stimulatory guanine nucleotide-binding regulatory component of adenylate cyclase （G_s） （GDP） ternary complex。

A cytosolic peptide ・ GTP complex which stimulates iota -isoproterenol- responsive adenylate cyclase activity was identified in the rat liver. The peptide component was purified and characterized with regard to its interaction with GTP in the regulation of adenylate cyclase. The peptide was isolated as a complex form with GTP on a Sephadex G-25 column in 1 mM NaHCO_3, and on the same column in 200 mM ammonium acetate it was purified as a dissociated form with Mr -3,000. The purified peptide alone displayed a markedly decreased stimulatory effect on adenylate cyclase activity, but its reassociated form with GTP clearly enhanced the effect of GTP on the enzyme activity. The isoproterenol competition curve using iota -[^3H]dihydroalprenolol (DHA) as an antagonist ligand shifted to lower affinity by the addition of the peptide reassociated with GTP (16.5-fold shift), while the same concentration of GTP (1 mu M) or the peptide alone had little or no effect (1.5- or 0.9-fold shift, respectively). Furthermore, the peptide enhanced the GTP effect in the response to iota -isoproterenol but not in that to glucagon, prostaglandin E_1 and fluoride. These results suggest that the peptide component of the cytosolic activator potentiates the effect of GTP on the agonist- beta -adrenergic receptor-stimulatory guanine nucleotide-binding regulatory component of adenylate cyclase (G_s) (GDP) ternary complex.