共查询到20条相似文献,搜索用时 15 毫秒
1.
Isolated human red blood cell membrane fragments (RBCMF) were found to take up Ca++ in the presence of ATP.1 This ATP-dependent Ca++ uptake by RBCMF appears to be the manifestation of an active Ca++ transport mechanism in the red cell membrane reported previously (Schatzmann, 1966; Lee and Shin, 1969). The influences of altering experimental conditions on Ca++-stimulated Mg++ ATPase (Ca++ ATPase) and Ca++ uptake of RBCMF were studied. It was found that pretreatment of RBCMF at 50°C abolished both Ca++ ATPase and Ca++ uptake. Pretreatment of RBCMF with phospholipases A and C decreased both Ca++ ATPase and Ca++ uptake, whereas pretreatment with phospholipase D did not significantly alter either Ca++ ATPase or Ca++ uptake. Both Ca++ ATPase and Ca++ uptake had ATP specificity, similar optimum pH's, and optimum incubation temperatures. From these results, it was concluded that Ca++ uptake is intimately linked to Ca++ ATPase. 相似文献
2.
The transfer of -phosphate from 32P labeled adenosine-triphosphate (ATP) at low concentrations (10?10 to 10?7M) into the peripheral nerve of the lobster was found to be highly sensitive to external ionic environments. The phosphorylation process is inhibited at conditions similar to extracellular environments (high Na+, Ca++ and pH) and stimulated by those close to intracellular medium (high K+, Mg++ and low pH). This system is not related to NaK ATPase (pump ATPase) which is highly sensitive to ouabain and is active only at higher ATP concentrations (>10?6M). The system is membrane bound and sensitive to a variety of neuro-active agents which are known to interfere with ionic conductance changes in axons. 相似文献
3.
K A Markossian R M Nalbandyan 《Biochemical and biophysical research communications》1975,67(3):870-876
An electrometric system was used to measure Ca++ uptake by sarcoplasmic reticulum vesicles (SR). The method permits continuous recording of Ca++ uptake and thus the valuation of kinetic parameters. Furthermore, the ultrasensitivity of the method permits to follow changes in Ca++ concentration below 10?6 M. 相似文献
4.
S M Aloj L D Kohn G Lee M F Meldolesi 《Biochemical and biophysical research communications》1977,74(3):1053-1059
The relationship between uptake of Ca++ and incorporation of sn-[14C]-glycerol-3-phosphate into phosphatidate, diglyceride, and triglyceride was evaluated in microsomes isolated from livers of normal fed male rats. Uptake of Ca++ was dependent on concentration of Ca++ (0.1 – 2.5 mM), and accompanied by a decrease in the rate of glycerolipid synthesis. The quantity of Ca++ ion taken up at 20 μM CaCl2 in the presence of ATP was equivalent to that observed with 2.5 mM CaCl2 in the absence of ATP. The ATP dependent uptake of Ca++, like the passive uptake at higher concentrations of Ca++, was correlated with inhibition of incorporation of sn-glycerol-3-phosphate into phosphatidate. Accumulation of Ca++ in hepatic microsomes, therefore, appears to result in a calcium-dependent decrease in biosynthesis of phosphatidate and other glycerolipids. 相似文献
5.
Active calcium ion uptake by inside-out and right side-out vesicles of red blood cell membranes 总被引:8,自引:3,他引:5
下载免费PDF全文
![点击此处可从《The Journal of general physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The relationship between active extrusion of Ca++ from red cell ghosts and active uptake of Ca++ by isolated red cell membrane fragments was investigated by studying the Ca++ uptake activities of inside-out and right side-out vesicles. Preparations A and B which had mainly inside-out and right side-out vesicles, respectively, were isolated from red cell membranes and were compared with respect to Ca++ adenosine triphosphatase (ATPase) and ATP-dependent Ca++ uptake activities. Preparation A had nearly eight times more inside-out vesicles and took up eight times more 45Ca in the presence of ATP compared to preparation B. Separation of the 45Ca-labeled membrane vesicles by density gradient centrifugation showed that the 45Ca label was localized to the inside-out vesicle fraction. In addition, the 45Ca taken up in the presence of ATP was lost during a subsequent incubation in the absence of ATP. The rate of 45Ca loss was not influenced by the presence of EGTA, but was slowed in the presence of La+8 (0.1 mM) in the efflux medium. The results presented here support the thesis that the active uptake of Ca++ by red cell membrane fragments is due to the active transport of Ca++ into inside-out vesicles. 相似文献
6.
Explants of fetal mouse spinal cord and cerebral cortex generate organotypic slow-wave and repetitive-spike discharges in vitro which can be abolished by agents which reduce the concentration of Ca++ available to the tissue. Synaptically mediated discharges are rapidly blocked in Ca++-free balanced salt solution (BSS), or in regular BSS after addition of 10?3 M EGTA, 5–10 × 10?3 M Mg++, or 10?4 M xylocaine, but simple spike potentials can still propagate. When low concentrations of cyclic AMP or dibutyryl cyclic AMP (2 × 10?6 M) are added to the Ca ++-free BSS or Ca++-antagonist-BSS, a temporary (1–20 min) restoration of characteristic complex bioelectric activities occurs (or the onset of depression is delayed if cyclic AMP is initially added). Phosphodiesterase inhibitors, e.g. 10?3 M caffeine, are also effective in restoring these blockades, whereas 5′AMP and ATP are not. Application of 10?6 M cyclic AMP or 10?3 M caffeine in regular BSS greatly enhances excitability of some CNS explants, resembling convulsive effects observed in CNS in situ. The data suggest that cyclic AMP can mobilize Ca++ from membranebound Ca pools within neurons in CNS explants so as to permit Ca++-dependent release of neurotransmitter during Ca++ deficits. Thus, it may also be that under normal conditions, cyclic AMP can regulate the availability of Ca++ for synaptic transmission in the central nervous system, thereby modulating the efficacy of synaptic functions. 相似文献
7.
R Wierichs A Hagenmeyer H Bader 《Biochemical and biophysical research communications》1980,92(4):1124-1129
Vanadate inhibits the Ca++-ATPase of sarcoplasmic reticulum from pig heart half maximally at about 10?5 M. Mg++ promotes this inhibition by vanadate whereas increasing Ca++-concentrations protect the enzyme against vanadate inhibition. Keeping the ratio constant there was no influence of ATP on the vanadate inhibition at concentrations up to 5 × 10?3 M ATP. Whenever the ratio was higher than 1:1 the inhibitory effect of vanadate on the Ca++-ATPase was increased. 相似文献
8.
The accumulation of Ca++ by microsomal (sarcotubular) preparations of rabbit skeletal muscle in the presence of oxalate, and the concurrent splitting of nucleoside triphosphate, displayed moderate nucleotide specificity in the sequence ATP > GTP, CTP, ITP > UTP > (ADP) > ATetraP for the former, ATP > (ADP) > ITP > GTP > CTP > UTP > ATetraP for the latter process. The "calcium pump" was weakly inhibited by caffeine, and was inhibited together with the ATPase by pyridoxalphosphate. Carnosine had no effect as such nor in the presence of pyridoxalphosphate except at high concentration; thiourea and p-chloromercuribenzoate were inhibiting while iodoacetate was inactive. Ca++ accumulation and ATPase were inhibited by atabrine (not tested on ATPase), dinitrophenol, and amytal. High concentrations of oligomycin and rutamycin inhibited Ca++ uptake while slightly stimulating ATPase. Antimycin A stimulated the Ca++ uptake. These results are discussed in the light of their possible relation to partial reactions in oxidative phosphorylation. The Ca++ uptake and relaxing factor activities did not behave identically throughout. This is in part ascribed to changes in reactivity of actomyosin in the relaxation test, in part to the participation of relaxing substances other than the calcium pump. 相似文献
9.
Roger F. Castilho Paulo C. Carvalho-Alves Anibal E. Vercesi Sérgio T. Ferreira 《Molecular and cellular biochemistry》1996,159(2):105-114
The major protein in the sarcoplasmic reticulum (SR) membrane is the Ca2+ transporting ATPase which carries out active Ca2+ pumping at the expense of ATP hydrolysis. The aim of this work was to elucidate the mechanisms by which oxidative stress induced by Fenton's reaction (Fe2+ + H2O2 HO· + OH–+ Fe3+) alters the function of SR. ATP hydrolysis by both SR vesicles (SRV) and purified ATPase was inhibited in a dose-dependent manner in the presence of 0–1.5 MM H2O2 plus 50 M Fe2+ and 6 mM ascorbate. Ca2+ uptake carried out by the Ca2+-ATPase in SRV was also inhibited in parallel. The inhibition of hydrolysis and Ca2+ uptake was not prevented by butylhydroxytoluene (BHT) at concentrations which significantly blocked formation of thiobarbituric acid-reactive substances (TBARS), suggesting that inhibition of the ATPase was not due to lipid peroxidation of the SR membrane. In addition, dithiothreitol (DTT) did not prevent inhibition of either ATPase activity or Ca2+ uptake, suggesting that inhibition was not related to oxidation of ATPase thiols. The passive efflux of 45Ca2+ from pre-loaded SR vesicles was greatly increased by oxidative stress and this effect could be only partially prevented (ca 20%) by addition of BHT or DTT. Trifluoperazine (which specifically binds to the Ca2+-ATPase, causing conformational changes in the enzyme) fully protected the ATPase activity against oxidative damage. These results suggest that the alterations in function observed upon oxidation of SRV are mainly due to direct effects on the Ca2+-ATPase. Electrophoretic analysis of oxidized Ca2+-ATPase revealed a decrease in intensity of the silver-stained 110 kDa Ca2+-ATPase band and the appearance of low molecular weight peptides (MW < 100 kDa) and high molecular weight protein aggregates. Presence of DTT during oxidation prevented the appearance of protein aggregates and caused a simultaneous increase in the amount of low molecular weight peptides. We propose that impairment of function of the Ca2+-pump may be related to aminoacid oxidation and fragmentation of the protein.Abbreviations AcP
acetylphosphate
- BHT
butylhydroxytoluene
- DTT
dithiothreitol
- Hepes
4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid
- SDS
sodium dodecyl sulfate
- SDS-PAGE
polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate
- SR
sarcoplasmic reticulum
- SRV
sarcoplasmic reticulum vesicles
- TBA
thiobarbituric acid
- TBARS
thiobarbituric acid-reactive substances
- TFP
trifluoperazine 相似文献
10.
P. Kutsky J.R. Falck G.B. Weiss S. Manna N. Chacos J. Capdevila 《Prostaglandins & other lipid mediators》1983,26(1):13-21
The 5,6- 8,9-; 11,12- and 14,15-epoxyeicosatrienoic acids and their respective hydration products, the vic-doisl, recently reported as metabolites of arachidonic acid in rat liver microsomes, were examined for effect on release of 45Ca from canine aortic smooth muscle miscrosomes. At 10−6 M, the diols had no effect, but the 5,6-; 11,12- and 14,15-epoxyacids increased the loss of 45Ca. Further studies with the 14,15-epoxyacid demonstrated a dose-dependent decrease of Ca++ uptake (ATP present) in canine aortic microsomes in 0.03 mM Ca++, whereass Ca++ binding (ATP absent) was not affected. Ca++ uptake, binding and release in rat liver microsomes was similarly affected by the 14,15-epoxyacid, the major epoxyeicosatrienoic acid derivative produced by rat liver miscrosomal incubations. It is suggested that a alterations in Ca++ metabolism might be a possible mechanism of actions for these derivatives of arachidonic acid. 相似文献
11.
Mechanisms for Intracellular Calcium Regulation in Heart : I. Stopped-Flow Measurements of Ca++ Uptake by Cardiac Mitochondria 总被引:11,自引:2,他引:9
下载免费PDF全文
![点击此处可从《The Journal of general physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Initial velocities of energy-dependent Ca++ uptake were measured by stopped-flow and dual-wavelength techniques in mitochondria isolated from hearts of rats, guinea pigs, squirrels, pigeons, and frogs. The rate of Ca++ uptake by rat heart mitochondria was 0.05 nmol/mg/s at 5 µM Ca++ and increased sigmoidally to 8 nmol/mg/s at 200 µM Ca++. A Hill plot of the data yields a straight line with slope n of 2, indicating a cooperativity for Ca++ transport in cardiac mitochondria. Comparable rates of Ca++ uptake and sigmoidal plots were obtained with mitochondria from other mammalian hearts. On the other hand, the rates of Ca++ uptake by frog heart mitochondria were higher at any Ca++ concentrations. The half-maximal rate of Ca++ transport was observed at 30, 60, 72, 87, 92 µM Ca++ for cardiac mitochondria from frog, squirrel, pigeon, guinea pig, and rat, respectively. The sigmoidicity and the high apparent Km render mitochondrial Ca++ uptake slow below 10 µM. At these concentrations the rate of Ca++ uptake by cardiac mitochondria in vitro and the amount of mitochondria present in the heart are not consistent with the amount of Ca++ to be sequestered in vivo during heart relaxation. Therefore, it appears that, at least in mammalian hearts, the energy-linked transport of Ca++ by mitochondria is inadequate for regulating the beat-to-beat Ca++ cycle. The results obtained and the proposed cooperativity for mitochondrial Ca++ uptake are discussed in terms of physiological regulation of intracellular Ca++ homeostasis in cardiac cells. 相似文献
12.
Effects of morphine tolerance and dependence on Mg++ dependent ATPase activity of synaptic vesicles.
The effect of morphine on ATPase of synaptic plasma membranes (SPM) and synaptic vesicles isolated from the mouse brain was studied. The activity of synaptic vesicle Mg++-dependent ATPase from mice rendered morphine tolerant and dependent by pellet implantation was 40% higher than that from placebo implanted mice. However, the activities of Mg++-dependent ATPase and Na+, K+ activated ATPase of SPM of tolerant and nontolerant mice were not significantly different. The activity of synaptic vesicular Mg++-dependet ATPase was dependent on the concentration of Mg++ but not of Ca++; maximum activity was obtained with 2 mM MgCl2. On the other hand, Mg++-dependent ATPase activity of SPM was dependent on both Mg++ and Ca++, activity being maximum using 2 mM MgCl2 and 10?5 M CaCl2. It is suggested that this stimulation of ATPase activity may alter synaptic transmission and may thus be involved in some aspects of morphine tolerance and dependence. 相似文献
13.
Summary We have shown that a Ca++-ionophore activity is present in the (Ca+++Mg++)-ATPase of rabbit skeletal muscle sarcoplasmic reticulum (A.E. Shamoo & D.H. MacLennan, 1974.Proc. Nat. Acad. Sci. USA
71:3522). Methylmercuric chloride inhibited the (Ca+++Mg++)-ATPase and Ca++ transport, but had no effect on the activity of the Ca++ ionophore. Mercuric chloride inhibited ATPase, transport and ionophore activity. The ATPase and transport functions were more sensitive to methylmercuric chloride than to mercuric chloride. The two functions were inhibited concomitantly by methylmercuric chloride but slightly lower concentrations of mercuric chloride were required to inhibit Ca++ transport than were required to inhibit ATPase. Methylmercuric chloride and mercuric chloride probably inhibited ATPase and Ca++ transport by blocking essential-SH groups. However, it appears that there are no essential-SH groups in the Ca++ ionophore and that mercuric chloride inhibited the Ca++ ionophore activity by competition with Ca++ for the ionophoric site. Blockage of Ca++ transport by mercuric chloride probably occurs both at sites of essential-SH groups and at sites of ionophoric activity. These data suggest the separate identity of the sites of ATP hydrolysis and of Ca++ ionophoric activity. 相似文献
14.
Our laboratory has recently reported that intestinal bile acid malabsorption in cystic fibrosis (CF) is a primary mucosal cell defect. Others have suggested that elevated intracellular Ca++ levels in other cell types in CF may represent a common primary dysfunction in Ca++ efflux in these cells. We examined the possibility that intestinal bile acid absorption and Ca++ efflux in mucosal cells may be linked physiologically. Brush border membrane vesicles (BBMV) prepared from guinea pig ileum served as the experimental model to test this hypothesis. Ca++ (2.5×10?3M) present in the incubation medium did not alter the uptake of taurocholic acid (TCA) by BBMV. Also, TCA uptake into BBMV preloaded with Ca++ was not significantly different from that in BBMV not previously loaded with Ca++. Furthermore, with TCA present in the incubation medium, Ca++ efflux from preloaded BBMV was not altered. These data suggest that ileal TCA uptake, as measured by BBMV, is not dependent upon either intra- or extravesicular Ca++. Also, Ca++ efflux from BBMV is unaffected by TCA uptake. Although separate lines of evidence suggest that intestinal bile acid malabsorption and reduced plasma membrane Ca++ flux are primary defects in CF, we conclude that in the normal intestine these functions are independent physiological processes. 相似文献
15.
M Kurebe 《Life sciences》1979,24(3):275-281
The delipidated Ca++-ATPase prepared from intestinal brush border membranes showed a higher activity of Ca++-independent ATPase, a lower Km value for ATP and a higher Km value for Ca++ than its original membrane Ca++-ATPase. The addition of phosphatidylcholine re-activated the delipidated Ca++-ATPase to approximately 89 % of its original membrane Ca++-ATPase activity but did not restore the affinity for Ca++. This phospholipid raised the Km value for ATP but had little effect on the Km value for Ca++. Palmitic acid elevated the Km value for Ca++ but did not change the Km value for ATP. Kinetic analyses of these data suggest that the hydrocarbon chain of phosphatidylcholine is an important rate-limiting factor for the access of Ca++ to the enzyme and the polar head groups of phosphorylcholine and ester bond may be the factor for the access of ATP. 相似文献
16.
R 24571: a new powerful inhibitor of red blood cell Ca++-transport ATPase and of calmodulin-regulated functions 总被引:21,自引:0,他引:21
K Gietzen A Wüthrich H Bader 《Biochemical and biophysical research communications》1981,101(2):418-425
Compound R 24571 (1-[bis(p-chlorophenyl)methyl]-3-[2,4-dichloro-β-(2,4-dichlorobenzyloxy)phenethyl]imidazoliniumchloride) is found to be a powerful inhibitor of red blood cell Ca++-ATPase as well as Ca++ transport into inside-out red blood cell vesicles with an IC50-value of 0.5 and 2 μM, respectively. The inhibitory action of R 24571 is more specific on the calmodulin-dependent fraction of Ca++-transport ATPase as compared to the basal Ca++-transport ATPase (determined in the absence of calmodulin) and can be antagonized by increasing concentrations of calmodulin in an apparently competitive manner. With respect to other ATPases the action of R 24571 is relatively specific for red blood cell Ca++-transport ATPase. Mg++-ATPase requires a 40 times higher concentration for halfmaximal inhibition (IC50 = 20 μM) whereas (Na+ + K+)-transport ATPase is only slightly affected in the investigated concentration range (≤20 μM). 相似文献
17.
Kabeer I. Ahammad Sahib Durisala Desaiah 《Journal of biochemical and molecular toxicology》1986,1(4):55-66
Previous studies from this laboratory have indicated that tricyclohexyltin hydroxide (Plictran) is a potent inhibitor of both basal- and isoproterenol-stimulated cardiac sarcoplasmic reticulum (SR) Ca2+-ATPase, with an estimated IC-50 of 2.5 × 10?8M. The present studies were initiated to evaluate the mechanism of inhibition of Ca2+-ATPase by Plictran. Data on substrate and cationic activation kinetics of Ca2+-ATPase indicated alteration of Vmax and Km by Plictran (1 and 5×10?8M), suggesting a mixed type of inhibition. The beta-adrenergic agonist isoproterenol increased Vmax of both ATP- and Ca2+-dependent enzyme activities. However, the Km of enzyme was decreased only for Ca2+ Plictran inhibited isoproterenol-stimulated Ca2+-ATPase activity by altering both and Vmax and Km of ATP as well as Ca2+-dependent enzyme activities, suggesting that after binding to a single independent site, Plictran inhibits enzyme catalysis by decreasing the affinity of enzyme for ATP as well as for Ca2+ Preincubation of enzyme with 15 μM cAMP or the addition of 2mM ATP to the reaction mixture resulted in slight activation of Plictran-inhibited enzyme. Pretreatment of SR with 5 × 10?7M propranolol and 5 × 10?8M Plictran resulted in inhibition of basal activity in addition to the loss of stimulated activity. Preincubation of heart SR preparation with 5 × 10?5M coenzyme A in combination with 5 × 10?8M Plictran partly restored the beta-adrenergic stimulation. These results suggest that some critical sites common to both basal- and beta-adrenergic-stimulated Ca2+-ATPase are sensitive to binding by Plictran, and the resultant conformational change may lead to inhibition of beta-adrenergic stimulation. 相似文献
18.
María P. Hortigón-Vinagre Solenne Chardonnet Cédric Montigny Yolanda Gutiérrez-Martín Philippe Champeil Fernando Henao 《Free radical biology & medicine》2011,50(11):1700-1713
Exposure of sarcoplasmic reticulum membranes to 4-hydroxy-2-nonenal (HNE) resulted in inhibition of the maximal ATPase activity and Ca2+ transport ability of SERCA1a, the Ca2+ pump in these membranes. The concomitant presence of ATP significantly protected SERCA1a ATPase activity from inhibition. ATP binding and phosphoenzyme formation from ATP were reduced after treatment with HNE, whereas Ca2+ binding to the high affinity sites was altered to a lower extent. HNE reacted with SH groups, some of which were identified by MALDI-TOF mass spectrometry, and competition studies with FITC indicated that HNE also reacted with Lys515 within the nucleotide binding pocket of SERCA1a. A remarkable fact was that both the steady-state ability of SR vesicles to sequester Ca2+ as well as the ATPase activity of SR membranes in the absence of added ionophore or detergent were sensitive to concentrations of HNE much smaller than those which affected the maximal ATPase activity of SERCA1a. This was due to increase in the passive permeability to Ca2+ of HNE-treated SR vesicles, an increase in permeability which did not arise from alteration of the lipid component of these vesicles. Judging from immunodetection with an anti-HNE antibody, this HNE-dependent increase in permeability probably arose from modification of proteins of about 150–170 kDa, present in very low abundance in longitudinal SR membranes (and in slightly larger abundance in SR terminal cisternae). HNE-induced promotion, via these proteins, of Ca2+ leakage pathways, might be involved in the general toxic effects of HNE. 相似文献
19.
Ca2+ binding by skeletal muscle microsomes in 5 mM ATP exhibited saturation kinetics in the range of Ca2+ concentrations between 3 · 10?8 and 10?5 M. Approximately 140 nmoles binding sites per mg protein were found. These had a Ca2+ binding constant of approximately 4.5 · 106 M?1 with half saturation at 2.2 · 10?7 M Ca2+. In the presence of oxalate, much larger amounts of Ca2+ (approx. 6 μmoles/mg protein) were taken up by the microsomes (Ca2+ uptake), but the rate of Ca2+ uptake increased linearly with [Ca2+] when ionized Ca2+ concentrations were below 3 · 10?6 M. At Ca2+ concentrations above 3 · 10?6, Ca2+ uptake was inhibited. Double reciprocal plots of the Ca2+ dependence of the initial rates of Ca2+ uptake in the concentration range between 3 · 10?7 M and 10?5 M, unlike those of Ca2+ binding, did not demonstrate saturation kinetics, but could be interpreted as representing a non-saturable system with inhibition at higher Ca2+ concentrations. In view of these differences, and because Ca2+-binding sites were almost fully saturated at 10?6 M Ca2+, whereas Ca2+ uptake rate increased linearly with increasing [Ca2+] to approximately 3 · 10?6 M, the Ca2+-binding sites are not shown kinetically to participate in oxalate-dependent Ca2+ uptake. 相似文献
20.
Jing Hui Xue Hiroko Takahashi Masayoshi Yamaguchi 《Journal of cellular biochemistry》2001,80(2):285-292
The effect of regucalcin, which is a regulatory protein of Ca2+ signaling, on Ca2+‐ATPase activity in isolated rat renal cortex mitochondria was investigated. The presence of regucalcin (50, 100, and 250 nM) in the enzyme reaction mixture led to a significant increase in Ca2+‐ATPase activity. Regucalcin significantly stimulated ATP‐dependent 45Ca2+ uptake by the mitochondria. Ruthenium red (10−6 M) or lanthunum chloride (10−6 M), an inhibitor of mitochondrial Ca2+ uptake, markedly inhibited regucalcin (100 nM)‐increased mitochondrial Ca2+‐ATPase activity and 45Ca2+ uptake. The effect of regucalcin (100 nM) in elevating Ca2+‐ATPase activity was completely prevented by the presence of digitonin (10−2%), a solubilizing reagent of membranous lipids, vanadate, an inhibitor of phosphorylation of ATPase, or dithiothreitol (50 mM), a protecting reagent of the sulfhydryl (SH) group of the enzyme. The activating effect of regucalcin (100 nM) on Ca2+‐ATPase activity was not further enhanced by calmodulin (0.30 μM) or dibutyryl cyclic AMP (10−4 M), which could increase Ca2+‐ATPase activity. Trifluoperazine (TFP; 50 μM), an antagonist of calmodulin, significantly decreased Ca2+‐ATPase activity. The activating effect of regucalcin on the enzyme was also seen in the presence of TFP, indicating that regucalcin's effect is not involved in mitochondrial calmodulin. The present study demonstrates that regucalcin can stimulate Ca2+‐pump activity in rat renal cortex mitochondria, and that the protein may act on an active site (SH group) related to phosphorylation of mitochondrial Ca2+‐ATPase. J. Cell. Biochem. 80:285–292, 2000. © 2000 Wiley‐Liss, Inc. 相似文献