Showing papers by "Ira Pastan published in 1970"
TL;DR: The action of cyclic AMP in E. coli may serve as a model to understand its action on transcriptional and translational processes in eukaryotes.
Abstract: Both cyclic AMP and a specific inducer acting in concert are required for the synthesis of many inducible enzymes in E. coli. Little enzyme is made in the absence of either. In contrast to the specific inducers which stimulate the synthesis only of the proteins required for their metabolism, cyclic AMP controls the synthesis of many proteins. Glucose and certain other carbohydrates decrease the differential rate of synthesis of inducible enzymes by lowering cyclic AMP concentrations. In the lac operon, cyclic AMP acts at the promoter site to facilitate initiation of transcription. This action requires another protein, the cyclic AMP receptor protein. The nucleotide stimulates tryptophanase synthesis at a translational level. The action of cyclic AMP in E. coli may serve as a model to understand its action on transcriptional and translational processes in eukaryotes.
472 citations
TL;DR: A cyclic AMP binding protein has been purified over 100-fold from E. coli extracts as mentioned in this paper, and this binding protein appears to be required for cyclicAMP action, they suggest it be called the cyclic amp receptor protein (CR protein).
Abstract: A cyclic AMP binding protein has been purified over 100-fold from E. coli extracts. Protein purified from wild-type strains binds cyclic AMP with an apparent dissociation constant of 1-2 × 10-6 M. Two mutant strains that are unresponsive to exogenous cyclic AMP have altered binding activity; the protein purified from one of these mutants has a decreased affinity for cyclic AMP (apparent dissociation constant = 2 × 10-5 M). Extracts of this mutant are deficient in their ability to support β-galactosidase synthesis in vitro. The addition of purified, wild-type binding protein to these extracts restores enzyme synthesis toward normal. Because this binding protein appears to be required for cyclic AMP action, we suggest it be called the cyclic AMP receptor protein (CR protein).
302 citations
TL;DR: This study demonstrates directly the binding of ACTH to its biologically significant site in direct proportion to their biological activity.
Abstract: Pure monoiodo ACTH-(125)I was prepared that was biologically active and free of unlabeled ACTH. Extracts of adrenal cortex that contained ACTH-sensitive adenyl cyclase, bound ACTH-(125)I; extracts that lacked the ACTH-sensitive cyclase did not bind ACTH-(125)I. Unlabeled ACTH inhibited the binding of ACTH-(125)I. Five ACTH derivatives which varied widely in biological activity were tested. All inhibited the binding of ACTH-(125)I in direct proportion to their biological activity. Albumin, insulin, and four unrelated iodinated hormones were inert. The addition of excess hormone or acetic acid produced rapid dissociation of bound ACTH-(125)I. This study demonstrates directly the binding of ACTH to its biologically significant site.
280 citations
TL;DR: This system, which appears to be applicable to all polypeptide hormones, provides a rapid and sensitive method for measurements of biologically active ACTH in dilute whole plasma.
Abstract: Biologically active iodine-125-labeled adrenocorticotropic hormone (ACTH) binds specifically to ACTH receptors extracted from adrenals. Unlabeled ACTH at 1 picogram per milliliter significantly displaces labeled ACTH from these receptors. This system, which appears to be applicable to all polypeptide hormones, provides a rapid and sensitive method for measurements of biologically active ACTH in dilute whole plasma.
150 citations
TL;DR: Calcium is thought to be required for the binding of adrenal corticotrophic hormone (ACTH) to its cellular receptor and inhibit the activation of adenyl cyclase by ACTH in subcellular particles from adipose and adrenal tissue.
Abstract: CALCIUM is thought to be required for the binding of adrenal corticotrophic hormone (ACTH) to its cellular receptor1–5: in its absence, ACTH fails to stimulate steroidogenesis in the adrenal or lipolysis in adipose tissue1,2,6,7. The actions of other lipolytic hormones such as adrenaline and glucagon do not require calcium1–3. On the other hand, high calcium concentrations (>1 mM) inhibit the activation of adenyl cyclase by ACTH in subcellular particles from adipose and adrenal tissue8,9. The sites of these effects of calcium have not been unequivocally located.
149 citations
TL;DR: It is demonstrated that cyclic adenosine 3',5'-monophosphate and glucose alter rates of mRNA production in proportion to their effects on β-galactosidase synthesis, and that these effects on lac mRNA synthesis are observed in cultures incapable of enzyme synthesis and that glucose does not affect the rate of degradation of lac mRNA.
68 citations
TL;DR: Cyclic 3′,5′-AMP increases the synthesis of lac mRNA in a cell-free extract of E. coli using λh80dlac DNA as template to be specific by competition of the 3 H-lac mRNA with unlabeled lac mRNA prepared from whole cells.
46 citations
34 citations
TL;DR: Adenyl cyclase from an ACTH sensitive adrenal tumor has been reduced to a molecular weight of 3 to 7 million by treatment of a lyophilized preparation of the particulate enzyme in a French pressure cell, a Nossal shaker or by sonication in the presence of both a phospholipid and fluoride.
Abstract: Adenyl cyclase from an ACTH sensitive adrenal tumor has been reduced to a molecular weight of 3 to 7 million by treatment of a lyophilized preparation of the particulate enzyme in a French pressure cell, a Nossal shaker or by sonication in the presence of both a phospholipid and fluoride. Phosphatidyl ethanolamine, phosphatidyl serine, dipalmitoyl lecithin, and sphingomyelin were all effective. No “solubilization” was achieved if either phospholipid or fluoride was omitted. The enzyme was activated by ACTH after the fluoride was removed by dialysis. The “soluble” adenyl cyclase was examined with the electron microscope. Negative staining with potassium phosphotungstate revealed a population of vesicular profiles ranging in size from 300–800 A, studded with granules of an average diameter of 90 A. Many of the 90 A granules were distributed singly unattached to the vesicles. A negative stained preparation of phospholipid alone revealed only the vesicular profiles. Following exposure of the particulate or the “soluble” enzyme to fluoride, persistent enzymatic activity was present despite removal of fluoride by dialysis. The addition of more fluoride stimulated the enzymatic activity to levels exceeding that of the undialyzed enzyme, suggesting removal of an inhibitor.
31 citations
30 citations
TL;DR: It is concluded that cyclic AMP, cyclicAMP receptor protein, an intact promoter locus, and other unidentified factor or factors are necessary for efficient transcription of the lac operon.
TL;DR: 2-mercapto-1(beta-4-pyridethyl)benzimidazole inhibited the development of antiviral activity induced by interferon in chick cells and the MPB effect was reversed by washing the cells.
Abstract: 2-mercapto-1(β-4-pyridethyl)benzimidazole (MPB) inhibited the development of antiviral activity induced by interferon in chick cells. The MPB effect was reversed by washing the cells. The action of MPB was on a step immediately following interferon binding but before the cellular RNA and protein synthesis that appear to be required for interferon action. The step blocked by MPB possibly involves cellular phospholipid synthesis.