Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have studied the effect of protein phosphokinase (EC 2.7.1.37; ATP:protein phosphotransferase) and phosphoprotein phosphatase (EC 3.1.3.16; phosphoprotein phosphohydrolase) on reverse transcriptase (RNA-dependent DNA nucleotidyltransferase) activity of Rous sarcoma virus. Protein kinase from Rous sarcoma virus-transformed chick embryo fibroblasts was purified by DEAE-cellulose chromatography, Sephadex gel filtration, and isoelectric focusing. Purified reverse transcriptase from Rouse sarcoma virus was preincubated with protein kinase and ATP under conditions allowing incorporation of phosphate into substrate protein. After the preincubation, reverse transcriptase activity was assayed in the presence of poly(rA).oligo(dT) as template. A 2- to 5-fold increase of reverse transcriptase activity was found after the preincubation of reverse transcriptase with protein kinase and ATP. Incubation of reverse transcriptase with heat-treated, inactive protein kinase and ATP had no effect on transcriptase activity. When the transcriptase preparation was incubated with protein kinase and [gamma-32P]ATP and subsequently purified by chromatography on phosphocellulose and Sephadex gel filtration, significant amounts of 32P-labeled proteins were found in the fractions exhibiting reverse transcriptase activity, suggesting 32P incorporation into transcriptase or transcriptase-associated proteins. A 20-60% decrease of reverse transcriptase activity was observed after incubation of reverse transcriptase with phosphatase. The results suggest that phosphorylative modification of reverse transcriptase may be critical in the regulation of reverse transcriptase-catalyzed DNA synthesis.
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PMID:Protein kinase and its regulatory effect on reverse transcriptase activity of Rous sarcoma virus. 5 72

1. We have used the patch-clamp technique to study modulation of the inwardly rectifying K+ current (IK(IR)) in cultured bovine pulmonary artery endothelial cells (CPAE cells). In whole-cell mode, IK(IR) was defined as the Ba(2+)-sensitive current. In single channel recordings, we observed a strongly inwardly rectifying and K(+)-selective channel with a conductance of 31 +/- 3 pS. 2. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and functional data suggest that the endothelial IRK is most probably Kir2.1. 3. Intracellular ATP is required to prevent run-down of IRK in whole-cell mode. Single channel activity disappeared in inside-out patches exposed to ATP-free solution and in cell-attached patches on cells exposed to metabolic inhibition (KCN, 2-deoxyglucose). 4. The non-hydrolysable ATP analogues, ATP gamma S and adenylyl imidodiphosphate (AMP-PNP), did not prevent run-down. Run-down did not occur in the presence of okadaic acid, a phosphatase inhibitor, but was enhanced in the presence of protamine, an activator of phosphatase 2A (PP2A). 5. GTP gamma S and AlF4- inhibited IRK, also in the presence of ATP. GTP beta S antagonized the GTP gamma S effect. Pretreatment of the cells with PTX did not affect the GTP gamma S-induced inhibition. Okadaic acid, however, slowed this inhibition. 6. Neither activation of protein kinase A (PKA) nor activation of protein kinase C (PKC) affected IRK. Additionally, neither cytochalasin B nor a high concentration of intracellular Ca2+ affected the time course of IRK run-down. 7. We conclude that run-down of IRK is probably due to dephosphorylation by PP2A. Activation of a PTX-insensitive G protein inhibits this current by a mechanism that is neither mediated via the PKA and PKC pathways nor by intracellular Ca2+, but supposedly by a G protein-dependent activation of a phosphatase.
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PMID:Modulation of inwardly rectifying potassium channels in cultured bovine pulmonary artery endothelial cells. 940 63

FK506, an immunosuppressant drug used to prevent allograft rejection in organ transplantations, accelerates functional recovery and nerve regeneration in the rat sciatic nerve crush model. While the mechanism by which FK506 increases regeneration is unknown, in contrast to immunosuppression, it does not involve calcineurin inhibition. Using the reverse-transcriptase polymerase chain reaction (RT-PCR) technique and a digoxigenin-labeled probe, we show that subcutaneous injections of FK506 (10 mg/kg/day) markedly increases the level of axotomy-induced growth-associated protein (GAP-43) mRNA in dorsal root ganglion (DRG) neurons. Quantitation of DRG neurons revealed that FK506 produced a 33% increase in the numbers of neurons exhibiting intense staining. Increased synthesis of GAP-43 may play a role in FK506's ability to speed nerve regeneration.
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PMID:The immunosuppressant FK506 increases GAP-43 mRNA levels in axotomized sensory neurons. 950 7

The transient outward K+ current (Ito) modulates transmembrane Ca2+ influx into cardiomyocytes, which, in turn, might act on Ito. Here, we investigated whether Ca2+ modifies functional expression of Ito. Whole-cell Ito were recorded using the patch clamp technique in single right ventricular myocytes isolated from adult rats and incubated for 24 h at 37 degrees C in a serum-free medium containing various Ca2+ concentrations ([Ca2+]o). Increasing the [Ca2+]o from 0.5 to 1.0 and 2.5 mM produced a gradual decrease in Ito density without change in current kinetics. Quantitativereverse transcriptase-PCR showed that a decrease of the Kv4.2 mRNA could account for this decrease. In the acetoxymethyl ester form of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM)-loaded myocytes (a permeant Ca2+ chelator), Ito density increased significantly when cells were exposed for 24 h to either 1 or 2.5 mM [Ca2+]o. Moreover, 24-h exposure to the Ca2+ channel agonist, Bay K8644, in 1 mM [Ca2+]o induced a decrease in Ito density, whereas the Ca2+ channel antagonist, nifedipine, blunted Ito decrease in 2.5 mM [Ca2+]o. The decrease of Ito in 2.5 mM [Ca2+]o was also prevented by co-incubation with either the calmodulin inhibitor W7 or the calcineurin inhibitors FK506 or cyclosporin A. Furthermore, in myocytes incubated for 24 h with 2.5 mM [Ca2+]o, calcineurin activity was significantly increased compared with 1 mM [Ca2+]o. Our data suggest that modulation of [Ca2+]i via L-type Ca2+ channels, which appears to involve the Ca2+/calmodulin-regulated protein phosphatase calcineurin, down-regulates the functional expression of Ito. This effect might be involved in many physiological and pathological modulations of Ito channel expression in cardiac cells, as well other cell types.
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PMID:Ca2+ controls functional expression of the cardiac K+ transient outward current via the calcineurin pathway. 1528 Mar 54