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

Acid shock of Chlamydomonas results in flagellar excision and induction of flagellar protein RNAs. The magnitude of flagellar RNA accumulations after flagellar excision by mechanical shear depends on the extracellular Ca2+ concentration. In this report, we demonstrate that the magnitude and duration of flagellar RNA accumulations are signaled by an acid shock-induced Ca2+ influx. RNA accumulations were greater in cells acid shocked in 500 microM CaCl2 than in 200 microM CaCl2, although the accumulation durations were similar. RNA accumulations of lower magnitude and shorter duration were observed in cells in Ca2+-containing buffer treated with CdCl2. RNA accumulations were of still lower magnitude and shorter duration in cells shocked in buffer without added CaCl2 than in cells shocked in 200 or 500 microM CaCl2 or in the presence of CdCl2. RNA accumulations similar to those in cells shocked in buffer without added CaCl2 were measured in cells following acid shock in buffer containing 200 microM CaCl2 and supplemented with neomycin, ruthenium red, or LaCl3. Acid shock of the adf-1 mutant resulted in RNA accumulations of shorter duration and lower magnitude than those measured in adf-1 cells stimulated by mechanical shear. These results are consistent with an hypothesis that acid shock generates two genetically and pharmacologically distinct signals governing flagellar RNA induction; the first signal is independent of a Ca2+ influx and flagellar excision and results in low magnitude accumulations of short duration, and the second is a consequence of a Ca2+ influx and results in accumulations of high magnitude and long duration.
Plant Mol Biol 1997 Feb
PMID:Calcium influx signals normal flagellar RNA induction following acid shock of Chlamydomonas reinhardtii. 904 67

A microassay is demonstrated for functional characterization of the Ca(2+)-release channel (CRC) of sarcoplasmic reticulum (SR) of skeletal muscle using swine with susceptibility to malignant hyperthermia (MH). Diluted muscle homogenates, indo-1 and ratiometric dual-emission spectrofluorometry are used to monitor Ca(2+)-lowering activity in real-time in the presence and absence of ryanodine at exposures that open and close the CRC. Reactions are initiated with 50 microM CaCl2 to raise ionized Ca2+ concentration near 1 microM and MgATP to activate the Ca(2+)-ATPase pump. Oxalate is included to precipitate Ca2+ within the SR. The assay requires less than 30 mg muscle, which may be cryopreserved, and is completed within 20 min of thawing the tissue. Maximum SR Ca(2+)-ATPase pumping and CRC activities, degree of CRC activation, and Ca(2+)-buffering capacity can be determined. Using this assay we studied muscle from MH-susceptible swine and demonstrated that whereas maximal Ca(2+)-ATPase pumping and CRC activities are normal, the CRC activity after addition of a bolus of Ca2+ is 50% greater in heterozygotes and 100% greater in homozygotes for the MH mutation. Hypersensitivity to CRC agonists, such as caffeine, and an associated hyposensitivity to CRC antagonists such as Mg2+ is also demonstrated. Genotypes for the MH mutation site can be discriminated from each other by determining Ca(2+)-lowering activities and the effect of ryanodine on them.
Mol Cell Biochem 1997 Feb
PMID:Rapid, simple and sensitive microassay for skeletal muscle homogenates in the functional assessment of the Ca-release channel of sarcoplasmic reticulum: application to diagnosis of susceptibility to malignant hyperthermia. 905 82

A low molecular weight heparin fraction with high anticoagulant activity was isolated from the precipitate of the interaction with the first component of the human complement system. Our results confirmed the predictions: under very strict conditions of pH (6.3), CaCl2 concentration (2 mM), ionic strength (25 mM) and protein/heparin ratio (1/1), the first component of the complement recognizes the high antithrombin III affinity fraction of heparin, and allows a concentration of the biological activity of the original low molecular weight-heparin.
Cell Mol Biol (Noisy-le-grand) 1997 Mar
PMID:The first component of the human complement system recognizes the active fraction of heparin. 913 Jun 7

The heptadecapeptide orphanin FQ (OFQ) has been identified as the endogenous ligand for a G protein-coupled receptor (OFQ-R), which, despite its high degree of sequence similarity to opioid receptors, fails to bind opioid ligands. We developed two radioligands for the OFQ-R: a tritiated native OFQ peptide ([3H]OFQ) and a radioiodinated form in which Leu14 was substituted by tyrosine (125I-Tyr14-OFQ). Their binding properties were examined in human embryonic kidney (HEK) 293 and Chinese hamster ovary (CHO) cells heterologously expressing the OFQ-R at different levels (HEK 293 expressed 40-fold more OFQ-R than did CHO). Both ligands exhibited rapid, monophasic association kinetics in each cell line. Dissociation of both ligands from OFQ-R expressed in HEK 293 cells was biphasic, whereas dissociation of 125I-Tyr14-OFQ from OFQ-R expressed in CHO cells was monophasic and slow. Saturation binding analysis revealed two affinity states in HEK 293 cells with binding parameters in accord with those determined kinetically. In CHO cells, 125I-Tyr14-OFQ detected a single affinity state with an intermediate Kd value of 54 pM. Optimal binding of the radioligands required 1-5 mM MgCl2, whereas millimolar concentrations of ZnCl2, CaCl2, MnCl2, and NaCl reduced specific binding of both ligands. A nonhydrolyzable GTP analog [guanosine-5'-(beta,gamma-imido)triphosphate] reduced the affinity of both OFQ ligands to their receptor without significant changes in the total binding capacity, indicating functional interactions between the OFQ-R and G proteins. In rat brain membranes, specific, saturable binding of 125I-Tyr14-OFQ was demonstrated to be pharmacologically identical to the heterologously expressed OFQ-R. Taken together, these results indicate that 125I-Tyr14-OFQ and [3H]OFQ exhibit virtually identical characteristics and are suitable for the pharmacological analysis of the OFQ-R.
Mol Pharmacol 1997 May
PMID:Interaction of [3H]orphanin FQ and 125I-Tyr14-orphanin FQ with the orphanin FQ receptor: kinetics and modulation by cations and guanine nucleotides. 914 20

Acetaldehyde (ACA), an ethanol metabolite, exerts both stimulatory and depressive effects on isolated myocardial tissue, but its impact on individual cardiac myocytes is unknown. The purpose of this study was to determine whether ACA-induced myocardial depression is due to an intrinsic alteration of the contractile properties of heart at the cellular level. Mechanical properties of adult rat ventricular myocytes were evaluated using a video edge-detection system. Myocytes were electrically stimulated to contract at 0.5 Hz under isotonic conditions in a physiological buffer containing 1 mM CaCl2. Contractile properties analyzed include: peak twitch amplitude (PTA), time-to-PTA (TPT), time-to-relengthening (TR90) and maximal velocities of shortening and relengthening (+/-dL/dt). Ca2+ transients were measured as fura-2 fluorescence intensity (FFI) changes. ACA (1-30 mM) disproportionately depressed PTA and FFI in a dose-dependent manner, with maximal inhibitions of 57 and 19%, respectively. Neither the durations nor maximal velocities of shortening and relengthening were affected by ACA. The depression of cell shortening by ACA was either attenuated or blocked by BayK 8644 or elevated extracellular Ca2+ (2.7 mM). In addition, ACA also reduced caffeine-induced FFI changes. These results suggest that ACA-induced myocardial depression in multicellular preparations is due to an intrinsic action on individual myocytes. The mechanism underlying ACA-induced myocardial depression may be due, in part, to either reduced Ca2+ entry through voltage-dependent Ca2+ channels and/or depression of sarcoplasmic reticular Ca2+ release.
Cell Mol Biol (Noisy-le-grand) 1997 Sep
PMID:Acetaldehyde depresses shortening and intracellular Ca2+ transients in adult rat ventricular myocytes. 935 29

FKS1 and FKS2 are alternative subunits of the glucan synthase complex, which is responsible for synthesizing 1,3-beta-glucan chains, the major structural polymer of the Saccharomyces cerevisiae cell wall. Expression of FKS1 predominates during growth under optimal conditions. In contrast, FKS2 expression is induced by mating pheromone, high extracellular [Ca2+], growth on poor carbon sources, or in an fks1 mutant. Induction of FKS2 expression in response to pheromone, CaCl2, or loss of FKS1 function requires the Ca2+/calmodulin-dependent protein phosphatase calcineurin. Therefore, a double mutant in calcineurin (CNB1) and FKS1 is inviable due to a deficiency in FKS2 expression. To identify novel regulators of FKS2 expression, we isolated genes whose overexpression obviates the calcineurin requirement for viability of an fks1 mutant. Two components of the cell integrity signaling pathway controlled by the RHO1 G protein (MKK1 and RLM1) were identified through this screen. This signaling pathway is activated during growth at moderately high temperatures. We demonstrate that calcineurin and the cell integrity pathway function in parallel, through separable promoter elements, to induce FKS2 expression during growth at 39 degrees C. Because RHO1 also serves as a regulatory subunit of the glucan synthase, our results define a regulatory circuit through which RHO1 controls both the activity of this enzyme complex and the expression of at least one of its components. We show also that FKS2 induction during growth on poor carbon sources is a response to glucose depletion and is under the control of the SNF1 protein kinase and the MIG1 transcriptional repressor. Finally, we show that FKS2 expression is induced as cells enter stationary phase through a SNF1-, calcineurin-, and cell integrity signaling-independent pathway.
Mol Cell Biol 1998 Feb
PMID:Temperature-induced expression of yeast FKS2 is under the dual control of protein kinase C and calcineurin. 944 98

The effect of regucalcin, a Ca2+-binding protein, on Ca2+ transport system in rat renal cortex microsomes was investigated. The presence of regucalcin (10[-8] to 10[-6] M) in the reaction mixture caused a significant increase in Ca2+-ATPase activity and ATP-dependent 45Ca2+ uptake in the microsomes. Regucalcin (10[-7] M) increased Ca2+-ATPase activity independently of increasing concentrations of CaCl2. The microsomal Ca2+-ATPase activity and 45Ca2+ uptake were markedly decreased by the presence of vanadate (0.1 mM) or N-ethylmaleimide (NEM; 5 mM) in the absence or presence of regucalcin. Dithiothreitol (DTT; 5 mM) markedly elevated Ca2+-ATPase activity and 45Ca2+ uptake in the microsomes. The DTT effects were not further enhanced by regucalcin (10[-7] M). Meanwhile, the microsomal Ca2+-ATPase activity and 45Ca2+ uptake were significantly decreased by the presence of dibutyryl cyclic AMP (DcAMP; 10[-5] and 10[-3] M) or inositol 1,4, 5-trisphosphate (IP3; 10[-7] and 10[-5] M). The effect of regucalcin (10[-7] M) on Ca2+ATPase activity and 45Ca2+ uptake was weakened in the presence of DcAMP or IP3. The present results demonstrate that regucalcin has a stimulatory effect on ATP-dependent Ca2+ uptake in the microsomes of rat renal cortex due to acting on the thiol groups of Ca2+-ATPase.
Mol Cell Biochem 1997 Dec
PMID:Regucalcin increases Ca2+-ATPase activity and ATP-dependent calcium uptake in the microsomes of rat kidney cortex. 945 Jun 63

The effect of regucalcin, a novel Ca2+-binding protein, on Ca2+/calmodulin-dependent cyclic adenosine monophosphate (AMP) phosphodiesterase activity in the cytosol of rat renal cortex was investigated. Regucalcin with physiologic concentration (10[-7] M) in rat kidney had no effect on cyclic AMP phosphodiesterase activity in the absence of CaCl2 and calmodulin. However, the activatory effect of both CaCl2 (10 microM) and calmodulin (20 U/ml) on cyclic AMP phosphodiesterase was markedly inhibited by the addition of regucalcin (10[-8] to 10[-6] M) in the enzyme reaction mixture. The inhibitory effect of regucalcin on the enzyme activity was also seen in the presence of CaCl2 (5-50 microM) or calmodulin (5-50 U/ml) with increasing concentrations. The presence of trifluoperazine (10 microM), an antagonist of calmodulin, caused a partial inhibition of Ca2+/calmodulin-dependent cyclic AMP phosphodiesterase activity. This inhibition was further enhanced by the addition of regucalcin (10[-7] M). The inhibitory effect of regucalcin (10[-7] M) was not seen in the presence of 20 microM trifluoperazine. Moreover, the activatory effect of calmodulin (20 U/ml) on cyclic AMP phosphodiesterase was not entirely seen, when calmodulin was added 10 min after incubation in the presence of CaCl2 (10 microM) and regucalcin (10[-7] M). The present results demonstrates that regucalcin has an inhibitory effect on Ca2+/calmodulin-dependent cyclic AMP phosphodiesterase activation in the cytosol of rat renal cortex.
Mol Cell Biochem 1997 Dec
PMID:Inhibitory effect of regucalcin on Ca2+/calmodulin-dependent cyclic AMP phosphodiesterase activity in rat kidney cytosol. 945 Jun 64

The effect of regucalcin on Ca2+/calmodulin-dependent protein kinase activity in the cytosol of rat renal cortex was investigated. Regucalcin is a calcium-binding protein which exists in rat liver and renal cortex. Protein kinase activity in renal cortex cytosol was markedly increased by the addition of CaCl2 (0.5 mM) plus calmodulin (10 microg/ml) in the enzyme reaction mixture . This increase was completely prevented by the addition of trifluoperazine (25 microM), an antagonist of calmodulin. The cytosolic Ca2+/calmodulin-dependent protein kinase activity was clearly inhibited by the addition of regucalcin; an appreciable effect of regucalcin was seen at 0.01 microM. The cytosolic Ca2+/calmodulin-dependent protein kinase activity was fairly increased by increasing concentrations of added Ca2+ (100-1000 microM). This increase was markedly blocked by the presence of regucalcin (0.1 microM). The inhibitory effect of regucalcin on the protein kinase activity was also seen with varying concentrations of calmodulin (2-20 microg/ml). These results demonstrate that regucalcin can regulate Ca2+/calmodulin-dependent protein kinase activity in renal cortex cells.
Mol Cell Biochem 1997 Dec
PMID:Inhibitory effect of regucalcin on Ca2+/calmodulin-dependent protein kinase activity in rat renal cortex cytosol. 945 Jun 68

The effects of the removal and replacement of divalent cations on the ultrastructure of 10 to 12 nm fibrillin-1-containing microfibrils have been studied, in order to investigate the conformation of fibrillin-1 calcium-binding epidermal growth factor-like (cbEGF-like) domains within the microfibril. The NMR structure of a covalently linked pair of cbEGF-like domains from fibrillin-1 recently identified a rigid rod-like conformation for the domain pair stabilised by interdomain calcium binding. This suggested that tandem arrays of fibrillin-1 cbEGF-like domains may adopt an extended conformation within a microfibril. If correct, then removal of bound calcium from fibrillin-1 would be expected to increase the flexibility of each cbEGF-like interdomain linkage, resulting in a decrease in the length of the interbead region of the microfibril (and thus a decrease in bead to bead periodicity), a concomitant increase in its diameter, and an overall increase in the flexibility of the microfibril. Our results show that removal of calcium by treatment with EGTA causes a large alteration of the microfibril structure, resulting in microfibrils with a reduced beaded periodicity, a disrupted interbead region and an increased overall flexibility. These effects are readily reversible by the re-addition of calcium (in the form of CaCl2), but not by the addition of magnesium (MgCl2). This is consistent with conformational changes in cbEGF-like domains causing the major structural effects on the microfibril. These results provide the first direct experimental evidence to support an extended rod-like conformation for multiple tandem repeats of fibrillin-1 cbEGF-like domains within the microfibril, as predicted by the NMR structure of an isolated fibrillin-1 cbEGF-like domain pair.
J Mol Biol 1998 Mar 13
PMID:Metal ion dependency of microfibrils supports a rod-like conformation for fibrillin-1 calcium-binding epidermal growth factor-like domains. 956 91


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