Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A truncated Bordetella pertussis cya gene product was expressed in Escherichia coli and purified by affinity chromatography on calmodulin-agarose. Trypsin cleavage of the 432-residue recombinant protein (Mr = 46,659) generated two fragments of 28 kDa and 19 kDa. These fragments, each containing a single Trp residue, were purified and analyzed for their catalytic and calmodulin-binding properties. The 28-kDa peptide, corresponding to the N-terminal domain of the recombinant adenylate cyclase, exhibited very low catalytic activity, and was still able to bind calmodulin weakly, as evidenced by using a fluorescent derivative of the activator protein. The 19-kDa peptide, corresponding to the C-terminal domain of the recombinant adenylate cyclase, interacted only with calmodulin as indicated by a shift in its intrinsic fluorescence emission spectrum or by the enhancement of fluorescence of dansyl-calmodulin. T28 and T19 fragments exhibited an increased sensitivity to denaturation by urea as compared to uncleaved adenylate cyclase, suggesting that interactive contacts between ordered portions of T28 and T19 in the intact protein participate both in their own stabilization and in stabilization of the whole tertiary structure. The two fragments reassociated into a highly active calmodulin-dependent species. Reassociation was enhanced by calmodulin itself, which 'trapped' the two complementary peptides into a stable, native-like, ternary complex, which shows similar catalytic properties to intact adenylate cyclase.
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PMID:Isolation and characterization of catalytic and calmodulin-binding domains of Bordetella pertussis adenylate cyclase. 200 7

Human choriogonadotropin (hCG) is a heterodimeric hormone consisting of an alpha subunit and a beta subunit. hCG and aglycosylated hCG (aghCG) have similar receptor binding affinities but differ in their ability to activate hormone-responsive adenylate cyclase. aghCG is an effective antagonist. The mechanisms of this antagonism and interactions of antagonistic aghCG with the receptor are not understood. To address this critical question, we have examined the interaction of this hormone analog with the receptor. The hormone receptor on porcine granulosa cells is a glycoprotein of 86 kDa and thas three domains of 24 kDa, 28 kDa, and 34 kDa, which are disulfide-linked. They undergo proteolysis, particularly when bound to the hormones, to produce three polypeptide components. These three receptor components can readily be identified through the use of affinity labeling with the hormones. Affinity labeling with an amino-specific homobifunctional reagent and subsequent cleavage indicate that hCG is cross-linked directly to the 24-kDa receptor component. In contrast, aghCG is cross-linked directly to the 34-kDa component. The peptide map of the cross-linked aghCG-34-kDa receptor component produced by papain treatment is different from the peptide map of the cross-linked complex of hCG-24-kDa component. This difference in receptor binding may be a factor determining the success or failure of signal transduction from the receptor to the effector system, guanine nucleotide-binding regulatory protein, and adenylate cyclase.
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PMID:Differential interactions of human choriogonadotropin and its antagonistic aglycosylated analog with their receptor. 234 45

Localization of adenylate cyclase activity in the outer cortical regions of the bovine lens correlates with the restriction of the Gs and Gi guanine nucleotide regulatory subunits of this enzyme to these same regions of the lens. In contrast, the major membrane substrates for cAMP-dependent protein kinase (cAMP-PK) (molecular masses of 18, 26 and 28 kDa) were identified in both the inner nuclear and the outer cortical regions of the lens. However, there were differences in the relative amounts of Pi incorporated into the 18 kDa and 28 kDa components in different lens regions. The three major membrane substrates for cAMP-PK were also phosphorylated when homogenates of lens cortex were incubated with [gamma-32P]ATP plus activators of the lens adenylate cyclase. In contrast, there was no incorporation of 32P into these substrates when homogenates of lens nucleus were used. When exogenous cAMP was added to homogenates of lens nucleus or cortex, 32P was incorporated into the membrane substrates for cAMP-PK in both regions of the lens, indicating that cAMP-PK was present in both regions. Interestingly, cAMP phosphodiesterase activity was at least 10-times greater in lens cortex than in the lens nucleus. These results indicate that while the major membrane substrates for cAMP-PK could be phosphorylated in all regions of the lens, there is a restriction of those enzymes that synthesize and degrade cAMP to the outer cortical regions of this organ.
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PMID:Regional distribution of the enzymes and substrates mediating the action of cAMP in the mammalian lens. 253 84

Spontaneously beating heart myocytes were prepared from adult rat ventricular tissues to study the correlation between beta-adrenergic receptor-stimulated changes in contractile performance and protein phosphorylation in vitro. The plasma membrane of isolated myocardial cells was permeabilized by saponin in the presence of EGTA and Mg-ATP. The permeabilized myocytes, which formed a homogeneous cell population, retained the rod-cell morphology of heart cells in situ and showed spontaneous cyclic contractions. Their contractile activity in response to extracellularly added cAMP mimicked the effects caused by beta-adrenergic stimulation of the whole heart: both the frequency and longitudinal velocity of free contraction and relaxation of the cells increased. Similar increases were observed when beta-agonist, isoproterenol, and GTP were added to suspending medium. In addition, isoproterenol maximally enhanced the adenylate cyclase activity of the cells in the presence of GTP. Both of these effects of isoproterenol were completely blocked by the beta-antagonist propranolol. cAMP-mediated phosphorylation of proteins in the permeabilized myocytes was investigated under conditions in which the beating frequency increased. cAMP elevated the phosphorylation level of five proteins; three of them with apparent molecular masses of 24, 15, and 12 kDa were membrane proteins and the other two with apparent molecular masses of 150 and 28 kDa were myofibrillar proteins. The 24-kDa phosphoprotein dissociated into 12-kDa molecules when boiled in sodium dodecyl sulfate, suggesting that these proteins are oligomeric and monomeric forms of phospholamban. The phosphorylation of these five proteins was stimulated by isoproterenol. The effect of isoproterenol was enhanced by GTP but completely blocked by propranolol. The time course of their phosphorylation correlated well with that of the increase in the beating frequency of the cells; both were measured after the administration of isoproterenol and GTP. When propranolol was added after the start of the stimulation by isoproterenol, only phospholamban and the 15-kDa protein were rapidly dephosphorylated in close correlation with the decrease of the beating frequency. These results demonstrate for the first time that the permeabilized myocytes retain the functional beta-adrenergic receptor and cellular responses to beta-adrenergic stimulation. They also suggest that cAMP-mediated phosphorylation of proteins, possibly phospholamban and/or the 15-kDa protein, is involved in the increased contractile activity of permeabilized heart cells.
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PMID:Beta-adrenergic regulation of contractility and protein phosphorylation in spontaneously beating isolated rat myocardial cells. 282 81

A cya-like gene encoding adenyl cyclase from Rhizobium meliloti was localized to a 0.8-kb PstI-EcoRI fragment by subcloning experiments. Experiments in Escherichia coli 'maxicells' identified a R. meliloti cya gene product of 28 kDa, which is significantly smaller than the corresponding protein from enteric bacteria. A control region for the expression of the cya gene in E. coli was found on an adjacent 2.6-kb BglII-BamHI sequence by insertional mutagenesis with Tn5 and phage MudI (ApR lac). The direction of transcription of the cya gene was also determined using a cya::MudIlac fusion. Promoter activity of this cya::lac fusion was not decreased when glucose was added to the culture. The R. meliloti cya gene is conserved among R. meliloti strains but no homology could be detected to other Rhizobium species or to E. coli in DNA hybridization experiments.
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PMID:Organization of the adenyl cyclase (cya) locus of Rhizobium meliloti. 302 93

Three GTP-binding proteins of 50 kDa, 45 kDa and 28 kDa were identified by photoaffinity labelling with [gamma-32P]GTP-gamma-azidoanilide (A-GTP) in the rat liver plasma membrane. Pertussis toxin catalysed ADP-ribosylation of a single protein of 40 kDa. A-GTP had no effect on the basal labeling by pertussis toxin. After u.v. irradiation of the membrane in the presence of A-GTP, the GTP-dependent ADP-ribosylation by cholera toxin was increased, while the basal labelling was not affected. These results suggest that A-GTP interacts specifically with the activatory GTP-binding protein (Gs) and does not interact with the inhibitory GTP-binding protein (Gi). The effects of partial photoinactivation of Gs of the rat liver plasma membrane adenylate cyclase system by A-GTP were studied. U.v. irradiation in the presence of increasing concentrations of the analogue caused progressive decrease in the maximal extent of activation by guanosine 5'-[gamma-thio]triphosphate, but the Ka was not affected. The rate of activation of liver adenylate cyclase by guanosine 5'-[gamma-thio]triphosphate is temperature-dependent. The lag time increased from 0.5 min at 30 degrees C to 2.0-2.5 min at 15 degrees C in the presence of 10 microM-guanosine 5'-[gamma-thio]triphosphate. However, Ka remains unaffected by lowering the temperature. Photoinactivation by A-GTP or competitive inhibition by guanosine 5'-[beta-thio]diphosphate decreases the maximal extent of activation by guanosine 5'-[gamma-thio] triphosphate, but the lag time remains unaffected. The present results support the idea that Gs is tightly associated with the catalytic subunit under basal conditions. The present results also indicate that the transition of an inactive Gs to its active form is the rate-limiting step of the activation of adenylate cyclase by guanosine 5'-[gamma-thio]triphosphate in the intact rat liver plasma membranes.
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PMID:The interactions between the activatory guanine nucleotide binding protein and the catalytic subunit of adenylate cyclase in rat liver plasma membranes. 393 89