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1.
Exposure of bovine pulmonary artery smooth muscle plasma membrane suspension with the oxidant H2O2 (1 mM) stimulated Ca2+ATPase activity. We sought to determine the role of matrix metalloprotease-2 (MMP-2) in stimulating Ca2+ATPase activity by H2O2 in the smooth muscle plasma membrane. The smooth muscle membrane possesses a Ca2+-dependent protease activity in the gelatin containing zymogram having an apparent molecular mass of 72 kDa. The 72 kDa protease
activity was found to be inhibited by EGTA, 1: 10-phenanthroline, a2-macroglobulin and tissue inhibitor of metalloprotease-2
(TIMP-2) indicating that the Ca2+-dependent 72 kDa protease is the MMP-2. Western immunoblot studies of the membrane suspension with polyclonal antibodies
of MMP-2 and TIMP-2 revealed that MMP-2 and TIMP-2, respectively, are the ambient matrix metalloprotease and the corresponding
tissue inhibitor of metalloprotease in the membrane.
In addition to increasing the Ca2+ATPase activity, H2O2 also enhanced the activity of the smooth muscle plasma membrane associated protease activity as evidenced by its ability
to degrade14C-gelatin. The protease activity and the Ca2+ATPase activity were prevented by the antioxidant, vitamin E, indicating that the effect produced by H2O2 was due to reactive oxidant species(es). Both basal and H2O2 stimulated MMP-2 activity and Ca2+ATPase activity were inhibited by the general inhibitors of matrix metalloproteases: EGTA, 1: 10-phenanthroline, α2-macroglobulin and also by TIMP-2 (the specific inhibitor of MMP-2) indicating that H2O2 increased MMP-2 activity and that subsequently stimulated Ca2+ATPase activity in the plasma membrane. This was further confirmed by the following observations: (i) adding low doses of
MMP-2 or H2O2 to the smooth muscle membrane suspension caused submaximal increase in Ca2+ATPase activity, and pretreatment with TIMP-2 prevents the increase in Ca2+ATPase activity; (ii) combined treatment of the membrane with low doses of MMP-2 and H2O2 augments further the Ca2+ATPase activity caused by the respective low doses of either H2O2 or MMP-2; and (iii) pretreatment with TIMP-2 prevents the increase in Ca2+ATPase activity in the membrane caused by the combined treatment of MMP-2 and H2O2. 相似文献
2.
Plant calcium pumps, similarly to animal Ca2+ pumps, belong to the superfamily of P-type ATPase comprising also the plasma membrane H+-ATPase of fungi and plants, Na+/K+ ATPase of animals and H+/K+ ATPase of mammalian gastric mucosa. According to their sensitivity to calmodulin the plant Ca2+-ATPases have been divided into two subgroups: type IIA (homologues of animal SERCA) and type IIB (homologues of animal PMCA).
Regardless of the similarities in a protein sequence, the plant Ca2+ pumps differ from those in animals in their cellular localization, structure and sensitivity to inhibitors. Genomic investigations
revealed multiplicity of plant Ca2+-ATPases; they are present not only in the plasma membranes and ER but also in membranes of most of the cell compartments,
such as vacuole, plastids, nucleus or Golgi apparatus. Studies using yeast mutants made possible the functional and biochemical
characterization of individual plant Ca2+-ATMPases. Plant calcium pumps play an essential role in signal transduction pathways, they are responsible for the regulation
of [Ca2+] in both cytoplasm and endomembrane compartments. These Ca2+-ATPases appear to be involved in plant adaptation to stress conditions, like salinity, chilling or anoxia. 相似文献
3.
Reduced expressions of calmodulin genes and protein and reduced ability of calmodulin to activate plasma membrane Ca2+‐ATPase in the brain of protein undernourished rats: modulatory roles of selenium and zinc supplementation
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Olusegun L. Adebayo Alka Khera Rajat Sandhir Gbenga A. Adenuga 《Cell biochemistry and function》2016,34(2):95-103
The roles of protein undernutrition as well as selenium (Se) and zinc (Zn) supplementation on the ability of calmodulin (CaM) to activate erythrocyte ghost membrane (EGM) Ca2+‐ATPase and the calmodulin genes and protein expressions in rat's cortex and cerebellum were investigated. Rats on adequate protein diet and protein‐undernourished (PU) rats were fed with diet containing 16% and 5% casein, respectively, for a period of 10 weeks. The rats were then supplemented with Se and Zn at a concentration of 0.15 and 227 mg l−1, respectively, in drinking water for 3 weeks. The results obtained from the study showed significant reductions in synaptosomal plasma membrane Ca2+‐ATPase (PMCA) activity, Ca2+/CaM activated EGM Ca2+ATPase activity and calmodulin genes and protein expressions in PU rats. Se or Zn supplementation improved the ability of Ca2+/CaM to activate EGM Ca2+‐ATPase and protein expressions. Se or Zn supplementation improved gene expression in the cerebellum but not in the cortex. Also, the activity of PMCA was significantly improved by Zn. In conclusion, it is postulated that Se and Zn might be beneficial antioxidants in protecting against neuronal dysfunction resulting from reduced level of calmodulin such as present in protein undernutrition. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
4.
The objective of this study was to investigate the influences of carbonyl stress induced by malondialdehyde (MDA), a typical
intermediate of lipid peroxidation, on intracellular free Ca2+ concentration ([Ca2+]i) alterations in cultured hippocampal neurons of rat. The microphotographic study clearly demonstrated that the hippocampal
neurons became gradually damaged following exposure to different concentrations of MDA. Further study indicated that the plasma
membrane Ca2+-ATPase (PMCA) activity was inhibited by MDA in a concentration- and time-dependent manner. The supplementation of 100 μM
MDA was found to cause a notable early phase increase of [Ca2+]i in hippocampal neuron cultures followed by a more pronounced late-phase elevation of [Ca2+]i. Such effect of MDA was prevented by the addition of nimodipine, an inhibitor of L-type calcium channel or by an extracellular
Ca2+ chelator EGTA. The identification of the calcium signalling pathways were studied by applying U73122, an inhibitor of PL-C,
and H-89, an inhibitor of protein kinase A (PKA), showing the involvement of PL-C/IP3 pathway but not the PKA/cAMP pathway.
These results suggested that MDA-related carbonyl stress caused damages of rat hippocampal neurons by triggering Ca2+ influx and influencing Ca2+ homeostasis in cultured neurons, and also MDA may act as a signalling molecule regulating Ca2+ release from intracellular stores. 相似文献
5.
A chicken pectoralis muscle membrane fraction enriched in a Mg2+- or Ca2+-activated (‘basic’) ATPase was obtained by sucrose gradient centrifugation. Enzymatic properties of the ‘basic’ ATPase were determined and used to localize its enzymatic activity in situ by ultrastructural cytochemistry. The enzyme was activated by Mg2+ or Ca2+ but not by Sr2+, Ba2+, Co2+, Ni2+ or Pb2+. It was present in a membranous fraction with a buoyant density of 1.10-1.12 (24–27.5% (w/w) sucrose). ‘Basic’ ATPase activity had a sedimentation pattern similar to the putative plasma membrane enzymes, 5′-nucleotidase and leucyl β-naphthylamidase, but different from that of sarcoplasmic reticulum Ca2+ ATPase. Also unlike sarcoplasmic reticulum Ca2+ ATPase, ‘basic’ ATPase was resistant to N-ethylmaleimide and aldehyde fixatives, was active in a medium containing a high Ca2+ concentration (3 mM), and was lost when exposed to Triton X-100 or deoxycholate. In cytochemical studies, a low Pb2+ concentration was used to capture the enzymatically released phosphate ions. Under conditions which eliminated interfering (Na+ + K+) ATPase and sarcoplasmic reticulum Ca2+ ATPase activities, electron-dense lead precipitates were present at the plasmalemma and T-system membranes. These studies suggest that ‘basic’ ATPase activity is associated with plasmalemma and T-system membranes of skeletal muscle. 相似文献
6.
Jiayu Liu Yufan Niu Jingjing Zhang Yuqing Zhou Zheng Ma Xuan Huang 《Plant Cell, Tissue and Organ Culture》2018,132(3):413-424
Calcium (Ca2+) signals are essential transducers and regulators in many adaptive and developmental processes in plants. Protective responses of plants to a variety of environmental stress factors are mediated by transient changes of Ca2+ concentration in plant cells. Ca2+ ions are quickly transported by channel proteins present on the plasma membrane. During responses to external stimuli, various signal molecules are transported directly from extracellular to intracellular compartments via Ca2+ channel proteins. Three types of Ca2+ channels have been identified in plant cell membranes: voltage-dependent Ca2+-permeable channels (VDCCs), which is sorted to depolarization-activated Ca2+-permeable channels (DACCs) and hyperpolarization-activated Ca2+-permeable channels (HACCs), voltage-independent Ca2+-permeable channels (VICCs). They make functions in the abiotic stress such as TPCs, CNGCs, MS channels, annexins which distribute in the organelles, plasma membrane, mitochondria, cytosol, intracelluar membrane. This review summarizes recent advances in our knowledge of many types of Ca2+ channels and Ca2+ signals involved in abiotic stress resistance and responses in plant cells. 相似文献
7.
Kannan Subburaj Elimban Vijayan Fandrich Robert R. Kardami Elissavet Dhalla Naranjan S. 《Molecular and cellular biochemistry》1999,197(1-2):187-194
Cardiac plasma membrane Ca2+/Mg2+ ecto-ATPase (myoglein) requires millimolar concentrations of either Ca2+ or Mg2+ for maximal activity. In this paper, we report its localization by employing an antiserum raised against the purified rat cardiac Ca2+/Mg2+ ATPase. As assessed by Western blot analysis, the antiserum and the purified immunoglobulin were specific for Ca2+/Mg2+ ecto-ATPase; no cross reaction was observed towards other membrane bound enzymes such as cardiac sarcoplasmic reticulum Ca2+-pump ATPase or sarcolemmal Ca2+-pump ATPase. On the other hand, the cardiac Ca2+/Mg2+ ecto-ATPase was not recognized by antibodies specific for either cardiac sarcoplasmic reticulum Ca2+-pump ATPase or plasma membrane Ca2+-pump ATPase. Furthermore, the immune serum inhibited the Ca2+/Mg2+ ecto-ATPase activity of the purified enzyme preparation. Immunofluorescence of cardiac tissue sections and neonatal cultured cardiomyocytes with the Ca2+/Mg2+ ecto-ATPase antibodies indicated the localization of Ca2+/Mg2+ ecto-ATPase in association with the plasma membrane of myocytes, in areas of cell-matrix or cell-cell contact. Staining for the Ca2+/Mg2+ ecto-ATPase was not cardiac specific since the antibodies detected the presence of membrane proteins in sections from skeletal muscle, brain, liver and kidney. The results indicate that Ca2+/Mg2+ ecto-ATPase is localized to the plasma membranes of cardiomyocytes as well as other tissues such as brain, liver, kidney and skeletal muscle. 相似文献
8.
The effects of ethanol in vitro on calmodulin-dependent Ca2+-activated ATPase (CaM–Ca2+-ATPase) activity were studied in synaptic plasma membranes (SPM) prepared from the brain of normal and chronically ethanol-treated rats. In SPM from normal animals, ethanol at 50–200 mM inhibited the Ca2+-ATPase activity. Lineweaver-Burk analysis indicates that the inhibition was the result of a decreased affinity of the enzyme for calmodulin, whereas the maximum activity of the enzyme was not changed. Arrhenius analysis indicates that the enzyme activity was influenced by lipid transition of the membranes, and ethanol in vitro resulted in a shift of the transition temperature toward a lower value. From animals receiving chronic ethanol treatment (3 weeks), the SPM were resistant to the inhibitory effect of ethanol on the enzyme activity. The resistance to ethanol inhibition was correlated with a higher enzyme affinity for calmodulin and a higher transition temperature, as compared with normal SPM. Since the calmodulin-dependent Ca2+-ATPase in synaptic plasma membranes is believed to be the Ca2+ pump controlling free Ca2+ levels in synaptic terminals, its inhibition by ethanol could therefore lead to altered synaptic activity.Abbreviations used ATPase
adenosine triphosphatase
- CaM
calmodulin
- CaM–Ca2+-ATPase
calmodulin-dependent Ca2+-activated ATPase
- EGTA
ethylene-bis(oxyethylenenitrilo)tetraacetic acid
- EtOH
ethanol
- Hepes
N—2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- SPM
synaptic plasma membranes
- TFP
trifluoperazine
- Tris
tris(hydroxymethyl)aminomethane
- Km
Michaelis constant
- Td
transition temperature
- Vmax
maximum velocity 相似文献
9.
Hongzhong Chen Liwen Wang Tetsuo Takano Shenkui Liu Xinxin Zhang 《Acta Physiologiae Plantarum》2016,38(4):94
Cation/H+ exchangers (CAXs) are membrane proteins that transport Ca2+ and other cations using the H+ gradient generated by H+-ATPase or H+-pyrophosphatase. This study reports the characterization of CAX2 from Puccinellia tenuiflora with respect to molecular and functional properties. PutCAX2 was cloned from a cDNA library of P. tenuiflora seedlings. The expression of PutCAX2 in shoots and roots was induced by Ca2+ and Ba2+ treatments. A green fluorescent protein (GFP) marker revealed that PutCAX2 was located on the endoplasmic reticulum (ER) membrane. Four yeast transformants were created using GFP fusion PutCAX2 and truncated PutCAX2s, and their growth in the presence of various cations (Fe3+, Al3+, Mn2+, Cu2+, Co2+, Ni2+, Mg2+, Zn2+, Na+, Li+, Ca2+, and Ba2+) was analyzed. The N-terminally truncated PutCAX2 (GFP-ΔNPutCAX2) and the N and C-terminally truncated PutCAX2 (GFP-ΔNCPutCAX2) transformants grew well in the presence of 100 and 150 mM Ca2+ or 8 and 20 mM Ba2+, whereas the GFP-PutCAX2 and C-terminally truncated PutCAX2 (GFP-ΔCPutCAX2) transformants did not show any tolerance to Ca2+ or Ba2+. The Ba2+ content in whole yeast cells expressing GFP-ΔNPutCAX2 or GFP-ΔNCPutCAX2 was lower than that in other yeast transformants. Moreover, the efflux experiment showed that the Ba2+ efflux rate of yeast cells expressing GFP-ΔNPutCAX2 and GFP-ΔNCPutCAX2 was higher than that of other yeast cells. To our knowledge, this is the first report on the molecular and functional characterization of a novel ER-localized CAX protein from a wild halophyte plant; the results suggest that the N-terminus of PutCAX2 acts as an auto-inhibitory domain, which affects the Ca2+ and Ba2+ tolerance of yeast. 相似文献
10.
Juyou Wu Cong Jin Haiyong Qu Xueting Jiang Jun Wu Guohua Xu Shaoling Zhang 《Acta Physiologiae Plantarum》2012,34(3):969-975
Calcium (Ca2+) plays crucial roles in regulation of pollen tube growth. The influx of Ca2+ into the pollen tube is mediated by ion channels, and the density and activity of Ca2+ channels in pollen plasma membranes critically determines their electrical properties. In this report, using whole-cell and single-channel patch-clamping techniques, we investigated developmental changes of hyperpolarization-activated Ca2+ channel activity in pear (Pyrus pyrifolia) pollen and its relationship with pollen viability. For both pollen and pollen tubes, hyperpolarization-activated Ca2+ channels had the same conductance and cAMP sensitivity, indicating that they were the same channels. However, the Ca2+ current density in pollen tube protoplasts was greater than that in pollen protoplasts. Compared with day-3 flowers’ pollen, hyperpolarization-activated Ca2+ current density was significantly lower in day 0 and day 3 flowers’ pollen, which was consistent with the pollen germination and pollen tube growth, indicating that pollen protoplasts’ increased Ca2+ current density may have enhanced the pollen viability. During pollen tube elongation, pollen tube plasma membrane Ca2+ current density increased with increased length pollen tubes up to 300 μm. All of these results indicated that hyperpolarization-activated Ca2+ channel activity was associated with in pear pollen development and may have a causal link between Ca2+ channel activity and pollen viability. 相似文献
11.
Powered by the mitochondrial membrane potential, Ca2+ permeates the mitochondria via a Ca2+ channel termed Ca2+ uniporter and is pumped out by a Na+/Ca2+ exchanger, both of which are located on the inner mitochondrial membrane. Mitochondrial Ca2+ transients are critical for metabolic activity and regulating global Ca2+ responses. On the other hand, failure to control mitochondrial Ca2+ is a hallmark of ischemic and neurodegenerative diseases. Despite their importance, identifying the uniporter and exchanger remains elusive and their inhibitors are non-specific. This review will focus on the mitochondrial exchanger, initially describing how it was molecularly identified and linked to a novel member of the Na+/Ca2+ exchanger superfamily termed NCLX. Molecular control of NCLX expression provides a selective tool to determine its physiological role in a variety of cell types. In lymphocytes, NCLX is essential for refilling the endoplasmic reticulum Ca2+ stores required for antigendependent signaling. Communication of NCLX with the store-operated channel in astroglia controls Ca2+ influx and thereby neuro-transmitter release and cell proliferation. The refilling of the Ca2+ stores in the sarcoplasmic reticulum, which is controlled by NCLX, determines the frequency of action potential and Ca2+ transients in cardiomyocytes. NCLX is emerging as a hub for integrating glucose-dependent Na+ and Ca2+ signaling in pancreatic β cells, and the specific molecular control of NCLX expression resolved the controversy regarding its role in neurons and β cells. Future studies on an NCLX knockdown mouse model and identification of human NCLX mutations are expected to determine the role of mitochondrial Ca2+ efflux in organ activity and whether NCLX inactivation is linked to ischemic and/or neurodegenerative syndromes. Structure-function analysis and protein analysis will identify the NCLX mode of regulation and its partners in the inner membrane of the mitochondria. 相似文献
12.
Identification and Characterization of the Ca-ATPase which Drives Active Transport of Ca at the Plasma Membrane of Radish Seedlings 总被引:1,自引:0,他引:1
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In microsomes from 24-hour-old radish (Raphanus sativus L.) seedlings ATP-dependent Ca2+ uptake occurs only in inside-out plasma membrane vesicles (F Rasi-Caldogno, MC Pugliarello, MI De Michelis [1987] Plant Physiol 83: 994-1000). A Ca2+-dependent ATPase activity can be shown in the same microsomes, when assays are performed at pH 7.5. The Ca2+-dependent ATPase is stimulated by the Ca2+ ionophore A23187 and is localized at the plasma membrane. Ca2+-dependent ATPase activity and ATP-dependent Ca2+ uptake present very similar saturation kinetics with erythrosin B (50% inhibition at about 0.1 micromolar), free Ca2+ (half-maximal rate at about 70 nanomolar), and MgATP (Km 15-20 micromolar). Ca2+ uptake can be sustained by GTP or ITP at about 60% the rate measured in the presence of ATP; only very low Ca2+ uptake is sustained by CTP or UTP and none by ADP. These results indicate that the Ca2+-ATPase described in this paper is the enzyme which drives active transport of Ca2+ at the plasma membrane of higher plants. 相似文献
13.
The anoxia-dependent elevation of cytosolic Ca2+ concentration, [Ca2+]cyt, was investigated in plants differing in tolerance to hypoxia. The [Ca2+]cyt was measured by fluorescence microscopy in single protoplasts loaded with the calcium-fluoroprobe Fura 2-AM. Imposition of
anoxia led to a fast (within 3 min) significant elevation of [Ca2+]cyt in rice leaf protoplasts. A tenfold drop in the external Ca2+ concentration (to 0.1 mM) resulted in considerable decrease of the [Ca2+]cyt shift. Rice root protoplasts reacted upon anoxia with higher amplitude. Addition of plasma membrane (verapamil, La3+ and EGTA) and intracellular membrane Ca2+-channel antagonists (Li+, ruthenium red and cyclosporine A) reduced the anoxic Ca2+-accumulation in rice. Wheat protoplasts responded to anoxia by smaller changes of [Ca2+]cyt. In wheat leaf protoplasts, the amplitude of the Ca2+-shift little depended on the external level of Ca2+. Wheat root protoplasts were characterized by a small shift of [Ca2+]cyt under anoxia. Plasmalemma Ca2+-channel blockers had little effect on the elevation of cytosolic Ca2+ in wheat protoplasts. Intact rice seedlings absorbed Ca2+ from the external medium under anoxic treatment. On the contrary, wheat seedlings were characterized by leakage of Ca2+. Verapamil abolished the Ca2+ influx in rice roots and Ca2+ efflux from wheat roots. Anoxia-induced [Ca2+]cyt elevation was high particularly in rice, a hypoxia-tolerant species. In conclusion, both external and internal Ca2+ stores are important for anoxic [Ca2+]cyt elevation in rice, whereas the hypoxia-intolerant wheat does not require external sources for [Ca2+]cyt rise. Leaf and root protoplasts similarly responded to anoxia, independent of their organ origin. 相似文献
14.
The distribution of ATPase activity in the heads of uncapacitated, capacitated, and acrosome-reacting guinea-pig spermatozoa was examined cytochemically using the Wachstein-Meisel's technique. In uncapacitated spermatozoa, the reaction products of the enzyme activity were localized on both the inner surface of the plasma membrane and the outer surface of the outer acrosomal membrane. The activity was Mg2+-dependent and inhibited by both Ca2+ and SH-blocking agents. This Mg2+-dependent ATPase activity was also demonstrated at the same sites in capacitated spermatozoa, whereas it was completely absent in acrosome-reacting spermatozoa. Although we did not determine the exact time of inactivation of the enzyme, it appeared to occur before the plasma membrane fused with the underlying outer acrosomal membrane. The abrupt loss of the Mg2+-dependent ATPase activity in the plasma and outer acrosomal membranes immediately before the onset of the acrosome reaction seems to suggest that inactivation of this enzyme by Ca2+ is one of the important biochemical events involved in the acrosome reaction. 相似文献
15.
Yeast suffers from a variety of environmental stresses, such as osmotic pressure and ethanol produced during fermentation.
Since calcium ions are protective for high concentrations of ethanol, we investigated whether Ca2+ flux occurs in response to ethanol stress. We find that exposure of yeast to ethanol induces a rise in the cytoplasmic concentration
of Ca2+. The response is enhanced in cells shifted to high-osmotic media containing proline, galactose, sorbitol, or mannitol. Suspension
of cells in proline and galactose-containing media increases the Ca2+ levels in the cytoplasm independent of ethanol exposure. The enhanced ability for ethanol to induce Ca2+ flux after the hypertonic shift is transient, decreasing rapidly over a period of seconds to minutes. There is partial recovery
of the response after zymolyase treatment, suggesting that cell wall integrity affects the ethanol-induced Ca2+ flux. Acetate inhibits the Ca2+ accumulation elicited by the ethanol/osmotic stress. The Ca2+ flux is primarily via the Cch1 Ca2+ influx channel because strains carrying deletions of the cch1 and mid1 genes show greater than 90% reduction in Ca2+ flux. Furthermore, a functional Cch1 channel reduced growth inhibition by ethanol. 相似文献
16.
Intracellular Ca2+ is vital for cell physiology. Disruption of Ca2+ homeostasis contributes to human diseases such as heart failure, neuron-degeneration, and diabetes. To ensure an effective
intracellular Ca2+ dynamics, various Ca2+ transport proteins localized in different cellular regions have to work in coordination. The central role of mitochondrial
Ca2+ transport mechanisms in responding to physiological Ca2+ pulses in cytosol is to take up Ca2+ for regulating energy production and shaping the amplitude and duration of Ca2+ transients in various micro-domains. Since the discovery that isolated mitochondria can take up large quantities of Ca2+ approximately 5 decades ago, extensive studies have been focused on the functional characterization and implication of ion
channels that dictate Ca2+ transport across the inner mitochondrial membrane. The mitochondrial Ca2+ uptake sensitive to non-specific inhibitors ruthenium red and Ru360 has long been considered as the activity of mitochondrial
Ca2+ uniporter (MCU). The general consensus is that MCU is dominantly or exclusively responsible for the mitochondrial Ca2+ influx. Since multiple Ca2+ influx mechanisms (e.g. L-, T-, and N-type Ca2+ channel) have their unique functions in the plasma membrane, it is plausible that mitochondrial inner membrane has more than
just MCU to decode complex intracellular Ca2+ signaling in various cell types. During the last decade, four molecular identities related to mitochondrial Ca2+ influx mechanisms have been identified. These are mitochondrial ryanodine receptor, mitochondrial uncoupling proteins, LETM1
(Ca2+/H+ exchanger), and MCU and its Ca2+ sensing regulatory subunit MICU1. Here, we briefly review recent progress in these and other reported mitochondrial Ca2+ influx pathways and their differences in kinetics, Ca2+ dependence, and pharmacological characteristics. Their potential physiological and pathological implications are also discussed. 相似文献
17.
Succinate production by a respiratory-deficient yeast was inibited by substances known to depolarize the plasma membrane. These substances include high concentrations of the permeable cation potassium, the ATPase inhibitor diethylstilbestrol, the polyene antibiotic amphotericin B, and the uncouplers carbonyl cyanidem-chlorophenylhydrazone and dinitrophenol. Results suggest that succinate effux from yeast cells is driven by membrane energization in the form of an electrical potential. As sucinate is one of the major by-products of alcoholic fermentation, deenergization of yeast plasma membrane may be a useful approach to increasing the yield of ethanol in industrial fermentations. 相似文献
18.
The plasma membrane was isolated from a calcareous red alga, Serraticardia maxima (Yendo) Silva (Corallinaceae), by aqueous two-phase partitioning. Its purity was examined with marker enzymes, Mg2+-dependent ATPase, inosine diphosphatase, cytochrome c oxidase and NADH-cytochrome c reductase, as well as the sensitivity of Mg2+-dependent ATPase to vanadate, azide and nitrate. The results showed that the isolated plasma membrane was purified enough to study its functions. Electron microscopic observations on thin tissue sections revealed that most vesicles of the isolated plasma membrane were stained by the plasma membrane specific stain, phosphotungstic acid-chromic acid. Mg2+- or Ca2+-dependent ATPases were associated with the plasma membrane. Ca2+-dependent ATPase was activated at physiological cytoplasmic concentrations of Ca2+ (0.1–10 μmol/L). However, calmodulin (0.5 μmol/L) did not affect its activity. The pH optimum was 8.0, in contrast to 7.0 for Mg2+-dependent ATPase. The isolated plasma membrane vesicles were mostly right side-out. To test for H+-translocation, right side-out vesicles were inverted; 27% of vesicles were inside-out after treatment with Triton X-100. The inside-out plasma membrane vesicles showed reduction of quinacrine fluorescence in the presence of 1 mmol/L ATP and 100 μmol/L Ca2+. The reduced fluorescence was recovered with the addition of 10 mmol/L NH4Cl, or 5 μmol/L nigericin plus 50 mmol/L KCl. UTP and CTP substituted for ATP, but ADP did not. Ca2+-dependent ATPase might pump H+ out in the physiological state. The acidification by this pump might be coupled with alkalinization at the calcifying sites, which induces calcification. 相似文献
19.
In the last few years, major progress has been made to elucidate the structure, function, and regulation of P-type plasma
membrane H+-and Ca2+-ATPases. Even though a number of regulatory proteins have been identified, many pieces are still lacking in order to understand
the complete regulatory mechanisms of these pumps. In plant plasma membrane H+- and Ca2+-ATPases, autoinhibitory domains are situated in the C- and N-terminal domains, respectively. A model for a common mechanism
of autoinhibition is discussed. 相似文献
20.
Das S Chakraborti T Mandal M Mandal A Chakraborti S 《Molecular and cellular biochemistry》2002,237(1-2):85-93
Treatment of bovine pulmonary artery smooth muscle plasma membrane suspension with the oxidant tert-butylhydroperoxide (t-buOOH) increases Ca2++ATPase activity. The smooth muscle plasma membrane possesses a Ca2++ dependent protease activity in the gelatin containing zymogram having an apparent molecular mass of 72 kDa. The 72 kDa protease activity was found to be inhibited by EGTA and the tissue inhibitor of metalloprotease-2 (TIMP-2). Since 72 kDa is the molecular mass of MMP-2 and since in our present study the 72 kDa protease in the gelatin containing zymogram is inhibited by matrix metalloprotease inhibitors, EGTA and TIMP-2, it may be suggested that the 72 kDa protease is the MMP-2. In addition to the increasing Ca2++ATPase activity, t-buOOH also enhances the activity of the membrane associated Ca2++ dependent protease that degrades 14C-gelatin. The oxidant triggered protease activity and the Ca2++ATPase activity were found to be prevented by the antioxidant vitamin E, and also by the Ca2++ dependent matrix metalloprotease inhibitors: EGTA and TIMP-2. Adding MMP-2 to the smooth muscle plasma membrane suspension caused an increase in Ca2++ATPase activity and pretreatment with TIMP-2 prevents the increase in Ca2++ATPase activity. Combined treatment of the smooth muscle plasma membrane with low doses of MMP-2 and t-buOOH augments further the Ca2++ATPase activity caused by the respective doses of either t-buOOH or MMP-2. Pretreatment with TIMP-2 prevents the increase in Ca2++ATPase activity elicited by the low doses of MMP-2 and/or t-buOOH. 相似文献