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

We have investigated the functional properties of four rat neuronal nicotinic acetylcholine receptor types expressed in Xenopus oocytes after injection of pairwise combinations of mRNA encoding alpha 2 or alpha 3 receptor subunits with mRNA encoding beta 2 or beta 4 receptor subunits. Current responses evoked by rapid application of cholinergic agonists (acetylcholine, nicotine, or 1,1-dimethyl-4-phenylpiperazinium) were recorded from voltage-clamped oocytes. Substituting BaCl2 for CaCl2 in the external solution increased the apparent Kd values of beta 4 subunit-containing receptors for acetylcholine but decreased the apparent Kd values of beta 2 subunit-containing receptors. Inhibition curves for the cholinergic antagonist (+)-tubocurarine were measured in BaCl2 medium at low agonist concentrations. (+)-Tubocurarine was a competitive antagonist of acetylcholine at neuronal nicotinic acetylcholine receptors that coexpressed the beta 2 subunit; the estimated Kb values were 3.6 microM (alpha 2 beta 2 receptors) and 390 nM (alpha 3 beta 2 receptors). In contrast, (+)-tubocurarine enhanced the peak responses evoked by low acetylcholine concentrations at alpha 2 beta 4 and alpha 3 beta 4 neuronal nicotinic acetylcholine receptors, without being a partial agonist. The maximal increase was observed at 5 microM and 10 microM (+)-tubocurarine for alpha 2 beta 4 and alpha 3 beta 4 receptors, respectively. Higher (+)-tubocurarine concentrations inhibited cholinergic responses, thus yielding a "bell-shaped" concentration-response curve.
Mol Pharmacol 1994 Dec
PMID:Unusual pharmacology of (+)-tubocurarine with rat neuronal nicotinic acetylcholine receptors containing beta 4 subunits. 780 38

Trypanosoma cruzi microsomes were found to possess membrane-bound alpha(1,2), alpha(1,3) and alpha(1,6) mannosidase activities that had an almost neutral optimum pH value, did not require CaCl2 for activity and were inhibited by swainsonine but not by deoxymannojirimycin. A mannosidase activity that degraded p-nitrophenylmannoside and that was inhibited by swainsonine was also present in the parasite microsomes. Experiments performed with intact cells showed that processing of protein-linked Man9GlcNAc2 was inhibited by deoxymannojirimycin but not by swainsonine. It was concluded that the activities detected were not involved in protein-linked Man9GlcNAc2 processing.
Cell Mol Biol (Noisy-le-grand) 1994 Nov
PMID:The presence in Trypanosoma cruzi microsomes of alpha(1,2), alpha(1,3) and alpha(1,6) mannosidase activities not involved in protein-linked Man9GlcNAc2 processing. 784 66

The action of carnitine in regulating fowl sperm motility was investigated. As the concentration of L-carnitine was increased (0-20 mM), the motility of intact and demembranated fowl spermatozoa was reduced at 30 degrees C. Even the presence of 1 mM CaCl2 before the addition of 10 mM carnitine could not prevent the inhibition of motility at 30 degrees C and 40 degrees C. However, motility was restored by reducing the concentrations of carnitine. Carnitine also inhibited the oxygen consumption and ATP concentrations of intact spermatozoa, and caused a reduction in intracellular free Ca2+ concentrations. Phosphorylation of a 50 kDa protein and dephosphorylation of 24 kDa and 30 kDa proteins of demembranated spermatozoa were observed after the addition of carnitine. In contrast, the flagellar ATPase activity of crude dynein extract was not affected by the addition of carnitine. These results suggest that inhibitory effect of carnitine for motility may be directly on the axonemal phosphoproteins, but not directly on the dynein ATPase activity. The physiological role of carnitine for fowl spermatozoa in the ductus deferens is discussed.
Mol Reprod Dev 1994 Jul
PMID:Inhibition of flagellar motility of fowl spermatozoa by L-carnitine: its relationship with respiration and phosphorylation of axonemal proteins. 791 83

Intact and permeabilized glioma C6 cells were incubated with [14C]serine in media containing low (100 nM) or high (2 mM) [Ca2+] and serine incorporation into phosphatidylserine was examined. In all cases thapsigargin, a blocker of the endoplasmic reticulum Ca(2+)-ATPase, diminished this process, whereas the action of the ionophore A23187 was dependent on the external calcium concentration and time of incubation. In permeabilized cells incubated at 100 nM Ca2+, serine incorporation into phosphatidylserine was diminished when the endoplasmic reticulum Ca2+ levels were lowered by the ionophore. In intact cells incubated at 2 mM CaCl2, addition of A23187 had no effect for the first 30 min and later decreased [14C]serine incorporation. This result seems to be not connected with the degradation of already formed phosphatidylserine, or with an enhanced metabolic conversion of this phospholipid, but with the decrease of its synthesis. The mechanism of this last process appears to be involved in the ionophore-induced perturbation of cellular Ca2+ homeostasis. Our results indicate that phosphatidylserine synthesis is a Ca(2+)-regulated process.
Biochem Mol Biol Int 1993 Dec
PMID:Effect of ionophore A23187 and thapsigargin on serine incorporation into phosphatidylserine in intact and permeabilized glioma C6 cells at high and low Ca2+ concentrations. 813 13

Metabotropic glutamate receptors (mGluRs) are G protein-linked receptors that operate through the formation of different second messengers. Utilizing quantitative autoradiographic techniques, we have characterized [3H]glutamate binding to mGluRs in discrete regions of adult rat brain. [3H]Glutamate binding, in the presence of high concentrations of alpha-amino-3-hydroxymethyl-4-isoxazolepropionic acid (10 microM), N-methyl-D-aspartate (100 microM), and 2.5 mM calcium chloride (CaCl2), was saturable. Scatchard plots were linear in all regions examined and revealed similar affinity constants of about 500 nM. The largest number of sites was found in the outer cerebral cortical layers (10 pmol/mg of protein). [3H]Glutamate binding was displaced by quisqualate, trans-1-amino-1,3-cyclopentane dicarboxylic acid (t-ACPD) (racemic mixture), and (1S,3R)-ACPD but not by (1R,3S)-ACPD. The guanine nucleotide analogue guanosine-5'-O-(3-thio) triphosphate (100 microM) reduced the binding by affecting the affinity but not the total number of sites, as predicted for G protein-coupled receptor sites. Quisqualate displacement curves were always biphasic and resolved two binding sites, with Ki values in the low nanomolar (15 nM) and micromolar (63 microM) ranges. (1S,3R)-ACPD displaced [3H]glutamate binding both in the absence and in the presence of 2.5 microM quisqualate, suggesting that both high and low affinity quisqualate sites are linked to mGluRs. (1S,3R)-ACPD competition curves were broad (Hill coefficient = 0.73) but monophasic under both conditions, with Ki values in the micromolar range (14-116 microM), suggesting that (1S,3R)-ACPD acts on the two quisqualate sites with similar apparent affinities. The regional distributions of the two sites were different. The highest levels of the high affinity quisqualate binding site were found in the cerebellar molecular layer. The highest levels of the low affinity quisqualate binding sites were found in the outer cerebral cortex. The pharmacological profile and regional distribution suggest that the high and low affinity quisqualate-sensitive components of [3H]glutamate binding sites might correspond to the mGluR1/mGluR5 and mGluR2/mGluR3 subgroups of cloned mGluRs, respectively.
Mol Pharmacol 1994 Apr
PMID:Metabotropic glutamate receptor heterogeneity in rat brain. 818 41

Crystals suitable for an X-ray diffraction investigation have been obtained of recombinant Coprinus cinereus peroxidase expressed in Aspergillus oryzae. The crystals were grown by the hanging drop method with polyethylene glycol 6000 as the precipitant. A pH range from 6.2 to 8.0 and CaCl2 or MgCl2 present at a concentration of 0.35 M were essential for the crystal growth. A metastable monoclinic modification can be obtained under certain conditions, and with variations in temperature they are transformed into a stable orthorhombic modification. With CaCl2 as the additive, the unit cell dimensions were a = 74.9 A, b = 76.8 A and c = 128.2 A. With two peroxidase molecules per asymmetric unit, the solvent content is 49% (v/v). In the diffraction pattern, the reflections Okl are systematically very weak for k = 2n + 1. Combined with an analysis of the Patterson function, this showed that the two independent molecules are related by the pseudotranslational symmetry 0.29a + 0.5b. The possible space groups are P2(1)2(1)2(1) or P2(1)22(1) because of this pseudosymmetry. The crystals diffract to a resolution of 2.9 A.
J Mol Biol 1993 Aug 05
PMID:Crystallization and X-ray diffraction analysis of recombinant Coprinus cinereus peroxidase. 839 39

Secretin, vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP) each exert potent positive contractile responses directly in rat ventricular cardiomyocytes. However, the contractile-coupling mechanisms associated with these responses have not been determined. In the present study, the involvement of L-type calcium channels in the contractile responses elicited by each peptide has been investigated using the selective antagonists at L-type calcium channels, verapamil and diltiazem. Ventricular cardiomyocytes, isolated from the hearts of adult rats, were stimulated to contract at 0.5 Hz in the presence of CaCl2 (2 mM) and adenosine deaminase (5U/ml). Cardiomyocytes were pre-incubated for 3 min prior to stimulation, in the absence of L-type calcium channel antagonist, and in the presence of verapamil (< or = 1 microM) or diltiazem (< or = 1 microM). Verapamil (< or = 1 microM) and diltiazem (< or = 1 microM) inhibited the contractile responses elicited by isoprenaline (100 nM) and forskolin (40 microM), used as positive controls, significantly, and in a concentration-dependent manner, but did not inhibit significantly the contractile response elicited by phenylephrine (2 microM), which was employed as a negative control. Verapamil (< or = 1 microM) and diltiazem (< or = 1 microM) inhibited the contractile responses to secretin (20 nM) and VIP (20 nM) significantly, and in a concentration-dependent manner, but did not inhibit the contractile response to CGRP. These data indicate that the positive contractile responses to secretin and VIP in mammalian ventricular cardiomyocytes involve the influx of calcium ion via L-type calcium channels, while the positive contractile response to CGRP does not.
J Mol Cell Cardiol 1995 Sep
PMID:Inhibition by verapamil and diltiazem of agonist-stimulated contractile responses in mammalian ventricular cardiomyocytes. 852 57

We have characterized the structure and expression of a senescence-associated gene (sen1) of Arabidopsis thaliana. The protein-coding region of the gene consists of 5 exons encoding 182 amino acids. The encoded peptide shows noticeable similarity to the bacterial sulfide dehydrogenase and 81% identity to the peptide encoded by the radish din1 gene. The 5'-upstream region contains sequence motifs resembling the heat-shock- and ABA-responsive elements and the TCA motif conserved among stress-inducible genes. Examination of the expression patterns of the sen1 gene under various senescing conditions along with measurements of photochemical efficiency and of chlorophyll content revealed that the sen1 gene expression is associated with Arabidopsis leaf senescence. During the normal growth phase, the gene is strongly induced in leaves at 25 days after germination when inflorescence stems are 2-3 cm high, and then the mRNA level is maintained at a comparable level in naturally senescing leaves. In addition, dark-induced senescence of detached leaves or of leaves in planta resulted in a high-level induction of the gene. Expression of the sen1 gene was also strongly induced in leaves subjected to senescence by 0.1mM abscisic acid or 1 mM ethephon treatment. The induced expression of the gene by dark treatment was not significantly repressed by treatment with 0.1 mM cytokinin or 50 mM CaCl2 which delayed loss of chlorophyll but not that of photochemical efficiency.
Plant Mol Biol 1996 Feb
PMID:A senescence-associated gene of Arabidopsis thaliana is distinctively regulated during natural and artificially induced leaf senescence. 862 6

Protein kinases are important in eukaryotic signal transduction pathways. In this study we designed degenerate oligonucleotides corresponding to two conserved regions of protein kinases and using the polymerase chain reaction (PCR) have amplified a 141 bp fragment of DNA from mungbeans (Vigna radiata Rwilcz cv. Berken). Sequence analysis of the PCR products indicates that they encode several putative protein kinases with respect to their identity with other known plant protein kinases. Using one of the six fragments (CPK3-8), we isolated a 2022 bp cDNA (VrCDPK-1) from a Vigna radiata lambda gt11 library. VrCDPK-1 has a 96 bp 5'-untranslated region and a 465 bp 3'-untranslated region and an open reading frame of 1461 bp. VrCDPK-1 contains all of the conserved regions commonly found in calcium dependent protein kinases (CDPK). VrCDPK-1 shares 24 to 89% sequence identity with previously reported sequences for plant CDPKs at the protein level. Southern analysis revealed the presence of several copies of the CDPK gene. VrCDPK-1 expression was stimulated when mungbean cuttings were treated with CaCl2, while treatment with MgCl2 had no effect. We are reporting for the first time a CDPK gene in mungbean which is inducible by mechanical strain. Cuttings treated with indole-3-acetic acid (IAA) or subjected to salt stress showed an increase in VrCDPK-1 expression. There was a dramatic stimulation in VrCDPK-1 expression 6 h after cuttings were treated with cycloheximide.
Plant Mol Biol 1996 Mar
PMID:Calcium-dependent protein kinase gene expression in response to physical and chemical stimuli in mungbean (Vigna radiata). 870 24

Fibrinogen showed essentially no binding (KD > 1 mM) to platelet alpha IIb beta 3 integrin in solution in the presence of Triton or octylglucoside above critical micellar concentrations. Under these conditions the integrin was an alpha beta monomer. After removal of the detergent from the Triton containing buffer (25 mM Tris/HCl;, 150 mM NaCl, 1 mM CaCl2, 1 mM MgCl2, pH 7.4) the integrin formed aggregates with hexamers as the most prominent species, as demonstrated by analytical ultracentrifugation and electron microscopy. Tracer sedimentation equilibrium experiments indicate that fibrinogen binds to the integrin aggregates, but with a surprisingly large KD (at least 3 microM). This value is 10- to 100-fold higher than values determined by solid phase assays or with integrins reconstituted onto lipid bilayers.
J Mol Recognit
PMID:Binding of fibrinogen to platelet integrin alpha IIb beta 3 in solution as monitored by tracer sedimentation equilibrium. 872 17


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