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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membrane responses to cyclic adenosine monophosphate (cAMP) injections have been studied by means of voltage clamp, Ca-indicator dye, and ion substitution techniques in identified neurons from the abdominal ganglion of Limax maximus. The ventral abdominal giant cell (AGC) displayed a response consisting of a decrease in outward current usually accompanied by a smaller enhancement of voltage-gated Ca2+ influx. Both responses were eliminated by external Cd2+ or Mn2+ and required membrane voltages more positive than -40 mV for expression. The enhanced influx persisted in Ba2+-substituted saline, while the decrease in outward current was blocked. A group of dorsal neurons (RD1-3, LD1) showed a mixed Na-Ca influx induced by cAMP that could be activated over a wide range of membrane potentials (less than -100 to greater than -20 mV). This flux caused a measurable increase in internal Ca2+. The influx was insensitive to Cd2+ and Mn2+ but was reduced by prolonged exposure to Co2+. The relative magnitude of the Na-Ca flux ratio showed considerable variation between specimens. In immature animals the Ca component was absent. The results demonstrated that elevation of intracellular cAMP can cause cell-specific changes of membrane conductance within closely associated neurons.
Cell Mol Neurobiol 1984 Dec
PMID:Alteration of calcium conductances and outward current by cyclic adenosine monophosphate (cAMP) in neurons of Limax maximus. 609 50

Palytoxin, isolated from the zoanthid Palytoha species, is one of the most potent marine toxins. Palytoxin (1 nM-1 microM) caused a release of [3H]norepinephrine from clonal rat pheochromocytoma cells in a concentration-dependent manner. This releasing action of palytoxin was markedly inhibited or abolished by Co2+ or Ca2+ -free medium, but was not modified by tetrodotoxin. The release of [3H]norepinephrine induced by a low concentration (30 nM) of palytoxin was abolished in sodium-free medium and increased as the external Na+ concentrations were increased from 3 to 100 nM, but the release induced by a high concentration (1 microM) was unaffected by varying the concentration of external Na+ from 0 to 100 mM. The release of [3H]norepinephrine induced by both concentrations of palytoxin increased with increasing Ca2+ concentrations from 0 to 3 mM. Palytoxin caused a concentration-dependent increase in 22Na and 45Ca influxes into pheochromocytoma cells at concentrations of 0.1 nM-10 nM and 1 nM-1 microM, respectively. The palytoxin-induced 45Ca influx was markedly inhibited by Co2+, whereas the palytoxin-induced 22Na influx was not affected by tetrodotoxin. These results suggest that in pheochromocytoma cells the [3H]norepinephrine release induced by lower concentrations of palytoxin is primarily brought about by increasing tetrodotoxin-insensitive Na+ permeability across the cell membrane, whereas that induced by higher concentrations is mainly caused by a direct increase in Ca2+ influx into them.
Mol Pharmacol 1984 May
PMID:Mechanism of palytoxin-induced [3H]norepinephrine release from a rat pheochromocytoma cell line. 614 92

It has been observed that growth of Escherichia coli cells are inhibited when treated with cobalt chloride (300 microM). It has also been shown that CoCl2 preferentially inhibits translation without inhibiting the process of transcription (1, 2, 8). We report here, that during treatment of E. coli cells with CoCl2, both messenger RNA and stable RNA synthesis is slowed down about 2.5 folds. The rate of degradation of mRNA also decreases and both chemical and functional half-life of mRNA increases about 2.5 folds in Co-treated cells. This clearly shows that the process of transcription is also affected while translation is preferentially inhibited during CoCl2 treatment.
Mol Biol Rep 1981 Aug 14
PMID:RNA synthesis and degradation during preferential inhibition of protein synthesis by cobalt chloride in Escherichia coli K-12. 616 83

Effects of Co2+ on the fast axonal transport of individual proteins were examined in vitro in bullfrog spinal/sciatic nerves. 35S-methionine-labeled proteins, fast-transported in control and Co2+-treated preparations were separated via two-dimensional gel electrophoresis. While the overall amount of protein transported was reduced, no qualitative differences could be seen when gel fluorographic patterns were compared. Quantitative analyses of the 48 most abundantly transported species revealed two significantly different populations (p less than 0.01) differentially sensitive to Co2+ and distinguishable to a large extent by molecular weight. Those proteins less sensitive to Co2+ ranged from approximately 20,000 to 35,000 daltons while those more sensitive to Co2+ were greater than approximately 35,000 daltons. The finding that all proteins are affected by Co2+ supports the proposal that fast-transported proteins are subject to a common Co2+-sensitive, Ca2+-requiring step. The observed differential effects are consistent with more than one Ca2+-dependent step occurring during the initiation phase of fast transport.
Cell Mol Neurobiol 1981 Mar
PMID:Differential effects of cobalt on the initiation of fast axonal transport. 617 23

With the use of the strain-overproducer restriction endonuclease R.EcoRV was isolated and purified to homogeneity. The molecular mass of the enzyme was determined by gel filtration and polyacrylamide gel electrophoresis to be 25 000 daltons. According to the data of immunological tests R.EcoRV differs in its antigenic characteristics from restriction endonucleases R.EcoRI and R.EcoRII. Dependence of enzyme activity on pH, ionic strength, temperature, presence of divalent cations (Mn2+, Mg2+, Co2+, Zn2+, Ni2+ and Cd2+) and organic solvents (glycerol, dimethylsulfoxide, ethanol) has been studied. It was shown that under conditions of replacement of Mg2+ for Mn2+ or after addition of organic solvents relaxation of R.EcoRV specificity takes place. It was shown also that R.EcoRV is able to digest T-even bacteriophage DNAs with different types and extents of modification. DNA modified by the action of MR.EcoRV system in vivo is susceptible to R.EcoRV in vitro. Under conditions of relaxed specificity noncanonical sites are susceptible to R.EcoRV attack. The fragments resulted may be cloned in canonical pBR322 EcoRV site.
Mol Biol (Mosk)
PMID:[EcoRV restrictase: physical and catalytic properties of homogenous enzyme]. 620 Jul 65

A new method of estimation of the distance RLM between the nitroxide spin label (NSL) and the paramagnetic metal ions (PMI), such as Co2+, Ni2+, Cu2+, Mn2+, VO2+, Cr3+, Fe3+ is suggested. The influence of the longitudinal relaxation time T1 of the PMI on the line shape of the NSL at 77 degrees K has been studied. It was found that the efficiency of the dipole-dipole interaction between NSL and PMI depends strongly on the T1 value of the PMI. Measurements of the RLM for 4 spin-labelled proteins (haemoglobin, nitrogenase, cytochrome P450 and Ca2+-dependent ATPase) by three various methods have proved the correctness of the new method and also its simplicity.
Mol Biol (Mosk)
PMID:[New method for measuring the distances between the nitroxide spin label and paramagnetic metal ions in macromolecules]. 626 67

The catalytic subunit of phosphoprotein phosphatase (Mr = 35,000) is inactivated by phosphate compounds such as trimetaphosphate, PPi, and ATP. The inactivation of phosphoprotein phosphatase by these phosphate compounds is time- and concentration-dependent, is not reversed by dilution or gel filtration and is protected by Pi. A dissociation constant for the enzyme-trimetaphosphate complex and a rate constant for the reaction were calculated to be 4.6 x 10(-4) M and 0.29 min-1, respectively. The inactivation of phosphatase by PPi and ATP shows more complex kinetics than that by trimetaphosphate. The addition of EDTA to PPi and ATP exhibits more potent inactivation, even though EDTA alone does not inactivate phosphatase. This phosphoprotein phosphatase is not labeled by [gamma-32P]ATP. The inactivation of phosphatase by PPi or ATP can only be reversed by Mn2+ or Co2+, among all other metals or cationic compounds tried. The reactivation also requires sulfhydryl compounds. The effectiveness of sulfhydryl compounds follows the order: dithioerythritol greater than mercaptoethanol greater than cysteine. Glutathione was without effect. Metal analysis of the catalytic subunit did not reveal any significant amounts of Ca, Cd, Co, Cu, Fe, Mg, Mn, Ni, Sn, or Zn. Phosphoprotein phosphatase activity from zinc-deficient rat livers also eliminated the possibility of this phosphatase being a zinc metalloenzyme. Inactivation does not seem to be due to a loss of a critical metal ion. Other mechanisms for inactivation are presented.
Mol Cell Biochem 1982 Jan 16
PMID:Inactivation and reactivation of phosphoprotein phosphatase. 627 82

Activation of muscarinic cholinergic receptors on 1321N1 human astrocytoma cells results in a 40-70% inhibition of isoproterenol- or prostaglandin E1 (PGE1)-stimulated accumulation of cyclic AMP. Previous investigations have demonstrated that this effect is due to a Ca2+-dependent activation of phosphodiesterase in the presence of muscarinic receptor agonists. However, during prolonged exposure of 1321N1 cells to a cholinergic agonist, a series of adaptive changes occurs which culminates in a complete loss of the muscarinic receptor-mediated inhibition of cyclic AMP accumulation. These alterations include: (a) A 50-100% increase in the capacity of isoproterenol and PGE1 to stimulate cyclic AMP accumulation. This phenomenon was rapid in onset, reached a maximum in 15-20 min, and disappeared over the next 2 hr even in the continued presence of carbachol. (b) A loss of the effects of muscarinic receptor stimulation on cyclic AMP accumulation. This phenomenon was apparent within 15 min after addition of carbachol, and complete desensitization was observed after 75 min. The loss of muscarinic receptor-mediated effects on cyclic AMP levels was due to a loss of the Ca2+-dependent stimulation of phosphodiesterase activity by muscarinic receptor agonists. (c) A loss of muscarinic receptors as assessed by [3H]quinuclidinyl benzilate binding. This effect was apparent after 90 min in the presence of carbachol. More than 80% of the receptors were lost after 24 hr, with no change occurring in the KD of [3H]quinuclidinyl benzilate. The concentration-effect curve for carbachol-induced changes in agonist responsiveness of the cyclic AMP system was similar to that for carbachol-induced reductions in cyclic AMP levels. Coincubation of carbachol with a saturating concentration of atropine prevented these adaptive changes from occurring. Although incubation of cells in Ca2+-free buffer or in the presence of 20 mM Co2+ prevented the inhibitory effects of muscarinic receptor stimulation on cyclic AMP accumulation, carbachol preincubations under these conditions still produced the adaptive changes in agonist responsiveness. The divalent cation ionophore, A23187, mimics the effects of muscarinic receptor stimulation on cyclic AMP levels by activating phosphodiesterase. Following complete carbachol-induced loss of responsiveness to muscarinic receptor agonists, A23187 was still capable of inhibiting cyclic AMP accumulation.
Mol Pharmacol 1983 Mar
PMID:Muscarinic cholinergic receptor-mediated control of cyclic AMP metabolism. Agonist-induced changes in nucleotide synthesis and degradation. 630 Jun 48

Hepatic pyruvate kinase phosphatase activity has been assayed in native conditions, in Sephadex G-25 filtered extracts of rat hepatocytes, by measuring the reactivation rate of glucagon-inactivated pyruvate kinase-L. The ionic requirements for this reaction, as well as the possible regulatory role of some pyruvate kinase ligands, have been investigated. Pyruvate kinase phosphatase activity was dependent on divalent cations (Mg2+, Mn2+ or Co2+). Mg2+ ions highly enhanced the reactivation rate of pyruvate kinase, while the presence of 100 mM KF inhibited this process. Physiological concentrations of phosphoenolpyruvate or fructose 1,6-bisphosphate inhibited pyruvate kinase phosphatase activity. These inhibitory effects were partially antagonized by the presence of L-alanine. Our results suggest that ligands of pyruvate kinase could play a role in the control of pyruvate kinase phosphatase activity(ies), possibly by modifying the conformational state of the substrate protein.
Mol Cell Biochem 1983
PMID:Modulation of pyruvate kinase phosphatase activity in hepatocyte extracts by pyruvate kinase-L ligands. 630 88

1. Spontaneous transmitter release was studied at the frog sartorius neuromuscular junction in the presence of a variety of cations before and after treatment with the specific presynaptic neurotoxin, beta-bungarotoxin (beta-BuTX). 2. Treatment with beta-BuTX produced a maintained increase in spontaneous release, as indicated by the miniature end-plate potential (m.e.p.p.) frequency. It was demonstrated that the m.e.p.p. frequency remained dependent on the extracellular calcium concentration. 3. A 30 mM increase in extracellular sodium chloride produced a reversible increase in frequency only after beta-BuTX treatment, indicating that beta-BuTX had increased the permeability of the presynaptic terminal. 4. Furthermore, several divalent cations other than calcium were shown to either maintain or greatly increase the m.e.p.p. frequency after beta-BuTX treatment (before toxin treatment replacement of calcium by these divalent cations produced only small changes in frequency). The relative effectiveness of the divalent cations tested in increasing spontaneous transmitter release after toxin treatment was Co2+ congruent to Ni2+ greater than Mg2+ greater than Ca2+ congruent to Sr2+ greater than Mn2+. The effect of cobalt, which increased the m.e.p.p. frequency 6.5 times after toxin treatment, was studied in detail.
Cell Mol Neurobiol 1982 Dec
PMID:Alterations in spontaneous transmitter release by divalent cations after treatment of the neuromuscular junction with beta-bungarotoxin. 630 1


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