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Cyclase

About: Cyclase is a research topic. Over the lifetime, 10162 publications have been published within this topic receiving 388566 citations.


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Journal ArticleDOI
01 Jul 2013-Mbio
TL;DR: The results support a model in which the formation of WspR-P subcellular clusters in vivo in response to a surface stimulus is important for potentiating the diguanylate cyclase activity of WSpR.
Abstract: WspR is a hybrid response regulator-diguanylate cyclase that is phosphorylated by the Wsp signal transduction complex in response to growth of Pseudomonas aeruginosa on surfaces. Active WspR produces cyclic di-GMP (c-di-GMP), which in turn stimulates biofilm formation. In previous work, we found that when activated by phosphorylation, yellow fluorescent protein (YFP)-tagged WspR forms clusters that are visible in individual cells by fluorescence microscopy. Unphosphorylated WspR is diffuse in cells and not visible. Thus, cluster formation is an assay for WspR signal transduction. To understand how and why WspR forms subcellular clusters, we analyzed cluster formation and the enzymatic activities of six single amino acid variants of WspR. In general, increased cluster formation correlated with increased in vivo and in vitro diguanylate cyclase activities of the variants. In addition, WspR specific activity was strongly concentration dependent in vitro , and the effect of the protein concentration on diguanylate cyclase activity was magnified when WspR was treated with the phosphor analog beryllium fluoride. Cluster formation appears to be an intrinsic property of phosphorylated WspR (WspR-P). These results support a model in which the formation of WspR-P subcellular clusters in vivo in response to a surface stimulus is important for potentiating the diguanylate cyclase activity of WspR. Subcellular cluster formation appears to be an additional means by which the activity of a response regulator protein can be regulated. IMPORTANCE Bacterial sensor proteins often phosphorylate cognate response regulator proteins when stimulated by an environmental signal. Phosphorylated response regulators then mediate an appropriate adaptive cellular response. About 6% of response regulator proteins have an enzymatic domain that is involved in producing or degrading cyclic di-GMP (c-di-GMP), a molecule that stimulates bacterial biofilm formation. In this work, we examined the in vivo and in vitro behavior of the response regulator-diguanylate cyclase WspR. When phosphorylated in response to a signal associated with surface growth, WspR has a tendency to form oligomers that are visible in cells as subcellular clusters. Our results show that the formation of phosphorylated WspR (WspR-P) subcellular clusters is important for potentiating the diguanylate cyclase activity of WspR-P, making it more active in c-di-GMP production. We conclude that oligomer formation visualized as subcellular clusters is an additional mechanism by which the activities of response regulator-diguanylate cyclases can be regulated.

121 citations

Journal ArticleDOI
TL;DR: Results indicate that the inhibition of CRF, (-)-isoproterenol, and VIP-stimulated ACTH secretion by SRIF may be regulated by its inhibitory action on adenylate cyclase.
Abstract: The AtT-20/D16-16 mouse pituitary tumor cell secretes corticotropin (ACTH) in response to corticotropin-releasing factor (CRF), (-)-isoproterenol, and vasoactive intestinal peptide (VIP). These responses are associated with a rapid increase in cyclic AMP formation. Somatostatin (SRIF) markedly decreases the stimulatory effect of CRF, (-)-isoproterenol, and VIP on both cyclic AMP formation and immunoreactive ACTH secretion. Forskolin and cholera toxin, adenylate cyclase activators, also stimulate cyclic AMP formation and ACTH secretion in AtT-20 cells and these responses are all inhibited by SRIF. The ACTH secretory responses to melittin and to the calcium ionophore A23187, neither of which increases cyclic AMP in AtT-20 cells, were not inhibited by SRIF. SRIF did not affect the binding of a tritiated beta-adrenergic receptor antagonist to AtT-20 membranes nor did it decrease basal cyclic AMP formation even in the presence of excess phosphodiesterase inhibitor, indicating that the reduction of cyclic AMP levels by SRIF did not involve either an interference with beta-adrenergic agonist binding to receptors or stimulation of cyclic AMP degradation. These results indicate that the inhibition of CRF-, (-)-isoproterenol-, and VIP-stimulated ACTH secretion by SRIF may be regulated by its inhibitory action on adenylate cyclase.

121 citations

Journal ArticleDOI
D Ochs1, C Kaletta1, K D Entian1, Annette G. Beck-Sickinger1, K Poralla1 
TL;DR: The pentacyclic hopanoids, a class of eubacterial lipids, are synthesized by squalene-hopene cyclase and side chain-elongating enzymes and no significant similarity to existing sequenced proteins was found.
Abstract: The pentacyclic hopanoids, a class of eubacterial lipids, are synthesized by squalene-hopene cyclase and side chain-elongating enzymes. With the aid of DNA probes based on the amino-terminal sequence of purified squalene-hopene cyclase from Bacillus acidocaldarius, clones of Escherichia coli that express this enzyme in the cytoplasmic membrane were isolated. According to the DNA sequence, the cyclase contained 627 amino acids with a molecular mass of 69,473 Da. A high percentage of the amino acids were basic. No significant similarity to existing sequenced proteins was found.

121 citations

Journal ArticleDOI
TL;DR: The effect of parathyroid hormone was much greater with tubules isolated from the renal cortex than with those from the medulla, and incorporating an ATP-regenerating system (phosphoenolpyruvates and pyruvate kinase) enhanced the sensitivity of the system.
Abstract: Tubules were isolated from kidneys of rats after incubation with collagenase and the effect of parathyroid hormone on adenyl cyclase in this tissue was studied. Adenyl cyclase in homogenates of tubules was assayed by measuring conversion of ATP-α-32P to cyclic 3′,5′-AM32P. Incorporating an ATP-regenerating system (phosphoenolpyruvate and pyruvate kinase) enhanced the sensitivity of the system. Virtually all of the enzyme activity in the renal cortex was found in the tubules. Parathyroid hormone caused rapid activation of the enzyme in tubules from the renal cortex; enzyme activity was directly proportional to the concentration of parathyroid hormone over the range of 0.05 to 5 μg/ml. The effect of parathyroid hormone was much greater with tubules isolated from the renal cortex than with those from the medulla. In contrast, arginine vasopressin activated the enzyme in the medulla but not the cortex. Epinephrine, glucagon and thyrocalcitonin caused an increase in enzyme activity but showed no dose-response ...

121 citations

Journal ArticleDOI
TL;DR: It is suggested that stimulation of PMN functions by chemoattractants may utilize an N-coupled process to generate a Ca2+ signal which could in turn raise intracellular cAMP levels indirectly and thereby provide negative regulation.

120 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202324
202257
202145
202048
201939
201856