共查询到20条相似文献,搜索用时 62 毫秒
1.
Lobão FA Façanha AR Okorokov LA Dutra KR Okorokova-Façanha AL 《FEMS microbiology letters》2007,274(1):17-23
The effect of aluminum on dimorphic fungi Yarrowia lipolytica was investigated. High aluminum (0.5–1.0 mM AlK(SO4 )2 ) inhibits yeast–hypha transition. Both vanadate-sensitive H+ transport and ATPase activities were increased in total membranes isolated from aluminum-treated cells, indicating that a plasma membrane H+ pump was stimulated by aluminum. Furthermore, Al-treated cells showed a stronger H+ efflux in solid medium. The present results suggest that alterations in the plasma membrane H+ transport might underline a pH signaling required for yeast/hyphal development. The data point to the cell surface pH as a determinant of morphogenesis of Y. lipolytica and the plasma membrane H+ -ATPase as a key factor of this process. 相似文献
2.
Terry A. Krulwich Arthur A. Guffanti Donna Seto-Young 《FEMS microbiology letters》1990,75(2-3):271-278
Abstract A Na+ /H+ antiporter catalyses coupled Na+ extrusion and H+ uptake across the membranes of extremely alkalophilic bacilli. This exchange is electrogenic, with H+ translocated inward > Na+ extruded. It is energized by the Δψ 2 component of the ΔμH+ that is established during primary proton pumping by the alkalophile respiratory chain complexes. These complexes abound in the membranes of extreme alkalophiles. Combined activity of the respiratory chain, the antiporter, and solute transport systems that are coupled to Na+ re-entry, allow the alkalophiles to maintain a cytoplasmic pH that is several pH units more acidic than optimal external pH values for growth. There is no compelling evidence for a specific and necessary role for any ion other than sodium in pH homeostasis, and although there is very high cytoplasmic buffering capacity in the alkaline range, active mechanisms for pH homeostasis are crucial. Energization of the antiporter as well as the proton translocating F 1 F 0 -ATPase that catalyses ATP synthesis in the extreme alkalophiles must accommodate the problem of the low net ΔμH+ and the very low concentrations of protons, per se, in the external medium. This problem is by-passed by other bioenergetic work functions, such as solute uptake or motility, that utilize sodium ions for energy-coupling in the place of protons. 相似文献
3.
Modulation of proton extrusion and ATP-dependent H+ transport through the plasma membrane in relation to the presence of 14-3-3 proteins in this membrane in response to osmotic shock was studied in tomato ( Lycopersicon esculentum Mill. cv. Pera) cell cultures. In vivo H+ extrusion by cells was activated rapidly and significantly after adding 100 m M NaCl, 100 m M KCl, 50 m M Na2 SO4 , 1.6% sorbitol or 2 µ M fusicoccin to the medium. The increase in H+ extrusion by cells treated with 100 m M NaCl was correlated with an increase of H+ transport by the plasma membrane H+ -ATPase (EC 3.6.1.35), but not with changes in ATP hydrolytic activity of this enzyme, suggesting an increased coupling ratio of the enzyme. Immunoblot experiments showed increased amounts of 14-3-3 proteins in plasma membrane fractions isolated from tomato cells treated with 100 m M NaCl as compared to control cells without changing the amount of plasma membrane H+ -ATPase. Together, these data indicate that in tomato cells an osmotic shock could enhance coupling between ATP hydrolysis and proton transport at the plasma membrane through the formation of a membrane 14-3-3/H+ -ATPase complex. 相似文献
4.
In higher plant cells, there are some enzymes capable of utilizing pyrophosphate (PPi ) as an energy donor. Among these, membrane-bound proton pumping pyrophosphatases (H+ -PPi ase) have been identified. In addition to the well-known vacuolar H+ -PPi ase (V-PPi ase), there is evidence for the presence of a mitochondrial H+ -PPi ase. This enzyme is localized on the inner surface of the inner membrane and catalyzes the specific hydrolysis of PPi , coupled to proton transport, with a H+ /PPi stoichiometry of ca 2. This activity is Mg2+ -requiring, is stimulated by monovalent cations, and is inhibited by Ca2+ , F− and diphosphonates. The H+ -PPi ase contains a catalytic head which is constituted by a 35-kDa protein which is loosely bound to the inner membrane. This protein exhibits a PPi ase activity, stimulated by phospholipids, with characteristics very similar to the membrane-bound enzyme. The mitochondrial PPi ase is distinct from the V-PPi ase, because an antibody raised against the 35-kDa protein does not react with tonoplast membranes. The mitochondrial H+ -PPi ase seems to have an F-type structure, similar to the F-ATP synthase and the membrane-bound PPi ases from mammalian and yeast mitochondria. It is suggested that, beside synthesizing PPi , this enzyme may act as a buffer for the electrochemical proton gradient, by hydrolyzing PPi, during conditions of oxygen deprivation. 相似文献
5.
Alexander Wiedenmann Peter Dimroth Christoph von Ballmoos 《Molecular microbiology》2009,72(2):479-490
F1 F0 ATP synthases use the electrochemical potential of H+ or Na+ across biological membranes to synthesize ATP by a rotary mechanism. In bacteria, the enzymes can act in reverse as ATP-driven ion pumps creating the indispensable membrane potential. Here, we demonstrate that the F0 parts of a Na+ - and H+ -dependent enzyme display major asymmetries with respect to their mode of operation, reflected by the requirement of ∼100 times higher Na+ or H+ concentrations for the synthesis compared with the hydrolysis of ATP. A similar asymmetry is observed during ion transport through isolated F0 parts, indicating different affinities for the binding sites in the a/c interface. Together with further data, we propose a model that provides a rationale for a differential usage of membrane potential and ion gradient during ATP synthesis as observed experimentally. The functional asymmetry might also reflect an important property of the ATP synthesis mechanism in vivo . In Escherichia coli , we observed respiratory chain-driven ATP production at pH 7–8, while P -site pH values < 6.5 were required for ATP synthesis in vitro . This discrepancy is discussed with respect to the hypothesis that during respiration lateral proton diffusion could lead to significant acidification at the membrane surface. 相似文献
6.
Michael Gjedde Palmgren Marianne Sommarin Peter Ulvlskov Peter Leth Jørgensen 《Physiologia plantarum》1988,74(1):11-19
Plasma membrane vesicles were purified from 8-day-old oat ( Avena sativa L. cv. Brighton) roots in an aqueous polymer two-phase system. The plasma membranes possessed high specific ATPase activity [ca 4 μmol P1 (mg protein)−1 min−1 at 37°C]. Addition of lysophosphatidylcholine (lyso-PC) produced a 2–3 fold activation of the plasma membrane ATPase, an effect due both to exposure of latent ATP binding sites and to a true activation of the enzyme. Lipid activation increased the affinity for ATP and caused a shift of the pH optimum of the H+ -ATPase activity to 6.75 as compared to pH 6.45 for the negative H+ -ATPase. Activation was dependent on the chain length of the acyl group of the lyso-PC, with maximal activition obtained by palmitoyl lyso-PC. Free fatty acids also activated the membrane-bound H+ -ATPase. This activation was also dependent on chain length and to the degree of unsaturation, with linolenic and arachidonic acid as the most efficient fatty acids. Exogenously added PC was hydrolyzed to lyso-PC and free fatty acids by an enzyme in the plasma membrane preparation, presumably of the phospholipase A type. Both lyso-PC and free fatty acids are products of phospholipase A2 (EC 3.1.1.4) action, and addition of phospholipase A2 from animal sources increased the H+ -ATPase activity within seconds. Interaction with lipids and fatty acids could thus be part of the regulatory system for H+ -ATPase activity in vivo, and the endogenous phospholipase may be involved in the regulation of the H+ -ATPase activity in the plasma membranne. 相似文献
7.
Abstract Cytochrome components which participate in the oxidation of nitrite in Nitrobacter winogradskyi have been highly purified and their properties studied in detail. Cytochrome a 1 c 1 is an iron-sulphur molybdoenzyme which has haems a and c and acts as a nitrite-cytochrome c oxidoreductase. Cytochrome c -550 is homologous to eukaryotic cytochrome c and acts as the electron mediator between cytochrome a 1 c 1 and aa 3 -type cytochrome c oxidase. The oxidase is composed of two kinds of subunits, has two molecules of haem a and two atoms of copper in the molecule, and oxidizes actively eukaryotic ferrocytochrome c as well as its own ferrocytochrome c -550. Further, a flavoenzyme has been obtained which has transhydrogenase activity and catalyses reduction of NADP+ with benzylviologen radical. This enzyme may be responsible for production of NADPH in N. winogradskyi . The electron transfer against redox potential from NO2 − to cythochrome c could be pushed through prompt removal by cytochrome aa 3 of H+ formed by the dehydrogenation of NO2 − + H2 O. As cytochrome c in anaerobically kept cell-free extracts is rapidly reduced on addition of NO2 − , a membrane potential does not seem necessary for the reduction of cytochrome c by cytochrome a 1 c 1 with NO2 − in vivo. 相似文献
8.
Abstract. Rates of proton extrusion and potassium (86 Rb) influx by intact roots of barley ( Hordeum vulgare cvs . Fergus, Conquest and Betzes) plants were simultaneously measured in short-term (15min) experiments. The nature and extent of apparent coupling between these ion fluxes was explored by manipulating conditions of temperature, pH and cation composition and concentration during flux determinations. In addition, the influence of salt status upon these fluxes was examined. At low K+ concentrations (0.01 to 1 mol m−3 ), H+ efflux and K+ influx were strongly correlated in both low- and high-K+ roots, although K+ : H+ exchange stoichiometries were almost consistently greater than 2:1. At higher concentrations (1 to 5 mol m−3 ), H+ efflux was either reduced or remained unchanged while K+ influxes increased. In the presence of Na2 SO4 , rates of H+ extrusion demonstrated similar cation dependence, although below 10 mol m−3 Na2 SO4 , H+ fluxes were generally 50% lower than in equivalent concentrations of K2 SO4 . These observations are considered in the context of current hypotheses regarding the mechanisms of k+ /H+ exchange. 相似文献
9.
YIYONG ZHU TINGJUN DI GUOHUA XU XI CHEN HOUQING ZENG FENG YAN & QIRONG SHEN 《Plant, cell & environment》2009,32(10):1428-1440
The preference of paddy rice for NH4 + rather than NO3 - is associated with its tolerance to low pH since a rhizosphere acidification occurs during NH4 + absorption. However, the adaptation of rice root to low pH has not been fully elucidated. This study investigated the acclimation of plasma membrane H+ -ATPase of rice root to low pH. Rice seedlings were grown either with NH4 + or NO3 - . For both nitrogen forms, the pH value of nutrient solutions was gradually adjusted to pH 6.5 or 3.0. After 4 d cultivation, hydrolytic H+ -ATPase activity, V max , K m , H+ -pumping activity, H+ permeability and pH gradient across the plasma membrane were significantly higher in rice roots grown at pH 3.0 than at 6.5, irrespective of the nitrogen forms supplied. The higher activity of plasma membrane H+ -ATPase of adapted rice roots was attributed to the increase in expression of OSA1, OSA3, OSA7, OSA8 and OSA9 genes, which resulted in an increase of H+ -ATPase protein concentration. In conclusion, a high regulation of various plasma membrane H+ -ATPase genes is responsible for the adaptation of rice roots to low pH. This mechanism may be partly responsible for the preference of rice plants to NH4 + nutrition. 相似文献
10.
Abstract A cytochrome aa3 terminal oxidase was isolated from protoplast membrane vesicles of Micrococcus luteus grown under aerobic conditions. The purified complex showed similarities to cytochrome c oxidase (EC 1.9.3.1) of the electron transport chain of mitochondria and many prokaryotes. The enzyme was solubilized by subsequent treatment with the detergents CHAPS and n-dodecyl-β-d-maltoside and purified by ion-exchange chromatography using poly-L-lysine agarose and TMAE-fractogel-650 (S) columns, followed by hydroxyapatite chromatography. The purified complex is composed of two major subunits with apparent molecular masses of 54 and 32 kDa. After purification the isolated enzyme contains 12.1 nmol of heme A (mg protein)−1 and exhibits absorption maxima at 424 nm and 598 nm in the oxidized state and at 442 nm and 599 nm in the reduced state. The CO-difference spectrum shows peaks at 428 and 590 nm which is indicative of heme a 3 , furthermore oxygen consumption was found to be sensitive to cyanide. 相似文献
11.
Lone Baunsgaard Kees Venema Kristian B. Axelsen José Manuel Villalba Annikki Welling Bernd Wollenweber Michael G. Palmgren 《The Plant journal : for cell and molecular biology》1996,10(3):451-458
Transport across the plasma membrane is driven by an electrochemical gradient of H+ ions generated by the plasma membrane proton pump (H+ -ATPase). Random mutants of Arabidopsis H+ -ATPase AHA1 were isolated by phenotypic selection of growth of transformed yeast cells in the absence of endogenous yeast H+ -ATPase (PMA1). A Trp-874-Leu substitution as well as a Trp-874 to Lys-935 deletion in the hydrophilic C-terminal domain of AHA1 conferred growth of yeast cells devoid of PMA1. A Trp-874-Phe substitution in AHA1 was produced by site-directed mutagenesis. The modified enzymes hydrolyzed ATP at 200–500% of wild-type level, had a sixfold increase in affinity for ATP (from 1.2 to 0.2 mM; pH 7.0), and had the acidic pH optimum shifted towards neutral pH. AHA1 did not contribute significantly to H+ extrusion by transformed yeast cells. The different species of aha1, however, displayed marked differences in initial rates of net H+ extrusion and in their ability to sustain an electrochemical H+ gradient. These results provide evidence that Trp-874 plays an important role in auto-inhibition of the plant H+ -ATPase and may be involved in controlling the degree of coupling between ATP hydrolysis and H+ pumping. Finally, these results demonstrate the usefulness of yeast as a generalized screening tool for isolating regulatory mutants of plants transporters. 相似文献
12.
YUKIO FUJINO KEIKO MITSUNAGA IKUO YASUMASU 《Development, growth & differentiation》1987,29(6):591-597
Embryos kept with omeprazole, a specific H+ , K+ -ATPase inhibitor, in a period of development between the mesenchyme blastula and the pluteus corresponding stage became abnormal plutei having quite small spicules, somewhat poor pluteus arms and apparently normal archenterons. In micro-mere-derived cells, kept with omeprazole at pH 8.2 in a period between 15 and 40 hr of culture at 20°C, omeprazole strongly inhibited spicule formation but did not block the outgrowth of pseudopodial cables, in which spicule rods were to be formed. These indicate that omeprazole probably exerts no obvious inhibitory effects other than spicule rods formation. Omeprazole-sensitive H+ , K+ -ATPase, an H+ pump, seems to be indispensable for CaCO3 deposition (formation of spicule rod) in these spicule forming cells. H+ , produced in overall reaction for CaCO3 formation: Ca2+ + CO2 +H2 O°CaCO3 +2H+ , is probably released from the cells by this H+ pump and hence, this reaction tends to go to CaCO3 production to form spicule rods. Omeprazole, known to become effective following its conversion to a specific inhibitor of H+ , K+ -ATPase at acidic pH, is able to inhibit formation of spicule rod at alkaline pH in sea water. This is probably due to an acidification of sea water near the cell surface by H+ ejection in H+ , K+ -ATPase reaction. 相似文献
13.
In vivo and in vitro effects of boron on the plasma membrane proton pump of sunflower roots 总被引:3,自引:0,他引:3
Marta Roldán rés Belver Pilar Rodríguez-Rosales Nuria Ferrol Juan Pedro Donaire 《Physiologia plantarum》1992,84(1):49-54
The effect of boron excess and deficiency on H+ efflux from excised roots from sunflower ( Heliarahus annuus L. cv. Enano) seedlings and on plasma membrane H+ -ATPase (EC 3.6.1.35) in isolated KI-washed microsomes has been investigated. When seedlings were grown in media with toxic levels of H3 BO3 (5 m M ) or without added boron and exposed to light conditions, an inhibition of the capacity for external acidification by excised roots was observed as compared to roots from seedlings grown with optimal H3 BO3 concentration (0.25 m M ). Toxic and deficient boron conditions also inhibited the vanadate-sensitive H+ -ATPase of microsomes isolated from the roots. The mechanism of boron toxicity was investigated in vitro with microsorne vesicles. A strong effect of boron on the vanadate-sensitive, ATP-dependent H+ transport was found, but the vanadate-sensitive phospho-bydrolase activity was not affected. These results suggest that boron could exert an effect on the plasma membrane properties, directly or indirectly regulating, proton transport. 相似文献
14.
Abstract: Using receptors expressed from mouse brain mRNA in Xenopus oocytes, we found that enhancement of type A γ-aminobutyric acid (GABAA ) receptor-gated Cl− channel response is a common action of structurally diverse anesthetics, suggesting that the GABAA receptor plays an important role in anesthesia. To determine if GABAA receptor subunit composition influences actions of anesthetics, we expressed subunit cRNAs in Xenopus oocytes and measured effects of enflurane on GABA-activated Cl− currents. Potentiation of GABA-activated currents by enflurane was dependent on the composition of GABAA receptor protein subunits; the order of sensitivity was α1 β1 > α1 β1 γ2s =α1 β1 γ2L > total mRNA. The results suggest that anesthetics with simple structures may act on the GABAA receptor protein complex to modulate the Cl− channel activity and provide a molecular explanation for the synergistic clinical interactions between benzodiazepines and general anesthetics. 相似文献
15.
Cleared maize ( Zea mays L. cv. LG 11) root homogenates were prepared and layered on the top of sucrose step gradients (10, 35 and 45%). The ATP- and pyrophosphate (PPi )-dependent proton-pumping activities were recovered almost completely at the 10%/35% interface, corresponding to the microsomal fraction (Golgi, tonoplast and endoplasmic reticulum). The PPi -dependent proton pump was characterized by the fluorescence quenching of quenching of quinacrine. The pH optimum was 7 to 8. The H+ -PPase was Mg2+ -dependent and the Km for PPi (in the presence of 3 m M MgSO4 ) was 28 μ M . The pump was electrogenic, K+ -dependent and a permeant anion was necessary to dissipate the membrane potential (NO3 − = I− >Br− > Cl− ). No activity was detected in the presence of electroneutral proton inonophores or, when valinomycin was added, with electrogenic ionophores. The H+ -PPase was insensitive to vanadate, oligomycin and molybdate. -Diethylstilbestrol (DES) and N,N'-dicyclohexylcarbodiimide (DCCD) were strongly inhibitory at 100 μ M . 相似文献
16.
KAORI KOHZUMA JEFFREY A. CRUZ KINYA AKASHI SAKI HOSHIYASU YURI NAKAJIMA MUNEKAGE AKIHO YOKOTA & DAVID M. KRAMER 《Plant, cell & environment》2009,32(3):209-219
Proton motive force (pmf) across thylakoid membranes is not only for harnessing solar energy for photosynthetic CO2 fixation, but also for triggering feedback regulation of photosystem II antenna. The mechanisms for balancing these two roles of the proton circuit under the long-term environmental stress, such as prolonged drought, have been poorly understood. In this study, we report on the response of wild watermelon thylakoid 'proton circuit' to drought stress using both in vivo spectroscopy and molecular analyses of the representative photosynthetic components. Although drought stress led to enhanced proton flux via a ∼34% increase in cyclic electron flow around photosystem I (PS I), an observed ∼fivefold decrease in proton conductivity, gH + , across thylakoid membranes suggested that decreased ATP synthase activity was the major factor for sustaining elevated qE . Western blotting analyses revealed that ATP synthase content decreased significantly, suggesting that quantitative control of the complex plays a pivotal role in down-regulation of gH + . The expression level of cytochrome b 6 f complex – another key control point in photosynthesis – also declined, probably to prevent excess-reduction of PS I electron acceptors. We conclude that plant acclimation to long-term environmental stress involves global changes in the photosynthetic proton circuit, in which ATP synthase represents the key control point for regulating the relationship between electron transfer and pmf. 相似文献
17.
Marco Zancani Valentino Casolo Angelo Vianello Francesco Macrí 《Physiologia plantarum》1998,103(3):304-311
The H+ /PPi stoichiometry of the mitochondrial H+ ‐PPi ase from pea ( Pisum sativum L.) stem was determined by two kinetic approaches, and compared with the H+ /substrate stoichiometries of the mitochondrial H+ ‐ATPase, and the vacuolar H+ ‐PPi ase and H+ ‐ATPase. Using sub‐mitochondrial particles or preparations enriched in vacuolar membranes, the rates of substrate‐dependent H+ ‐transport were evaluated: by a mathematical model, describing the time‐course of H+ ‐gradient (ΔpH) formation; or by determining the rate of H+ ‐leakage following H+ ‐pumping inhibition by EDTA at the steady‐state ΔpH. When the H+ ‐transport rates were divided by those of PPi or ATP hydrolysis, measured under identical conditions, apparent stoichiometries of ca 2 were determined for the mitochondrial H+ ‐PPi ase and H+ ‐ATPase, and for the vacuolar H+ ‐ATPase. The stoichiometry of the vacuolar H+ ‐PPi ase was found to be ca 1. From these results, it is suggested that the mitochondrial H+ ‐PPi ase may, in theory, function as a primary H+ ‐pump poised towards synthesis of PPi and, therefore, acting in parallel with the main H+ ‐ATPase. 相似文献
18.
19.
Abstract Washed cells of Rhodopseudomonas sphaeroides forma sp. denitrificans , grown under photodenitrifying conditions, exhibited K+ uptake dependent on the transmembrane proton gradient (Δ pH). These cells also acidified the suspension medium in response to K+ pulses both aerobically and anaerobically in light and in the dark. The results indicate that the photodenitrifier has a reversible K+ /H+ exchange activity which reflects its role in regulating the intracellular K+ concentration, as well as intracellular pH. The acidification of the external medium resulting from K+ pulses was inhibited by carbonyl cyanide- m -chlorophenylhydrazone (CCCP) indicating that the antiporter is energy-dependent. Addition of KCl to washed cells depolarized the membrane potential (Δψ) with a concomitant increase in ΔpH, indicating that the K+ /H+ antiporter was electrogenic. 相似文献
20.
C. A. E. M. van Hooijdonk R. M. L. Colbers J. Piek & P. E. J. van Erp 《Cell proliferation》1997,30(8):351-364
In many cell types cytoplasmic alkalization is an early marker for cell activation. An amiloride-sensitive Na+ /H+ exchanger is an important regulator of this process. However, in keratinocytes the existence of a Na+ /H+ exchanger nor a proliferation-associated increase in intracellular pH (pHi ) has been demonstrated.
The aim of this study was to investigate whether or not keratinocytes, derived from the BALB/MK cell line, contain a Na+ /H+ exchanger and whether cytoplasmic alkalization is proliferation-associated in these cells. This mouse keratinocyte cell line can easily be switched between a proliferative and a quiescent state under defined culture conditions. The novel pH-sensitive dye seminaphthorhodafluor (SNARF)-calcein proved to be very suitable for flow cytometric pHi measurements in BALB/MK cells. Initial measurements of the pHi using a cocktail of the established fluorochromes 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF) and SNARF-1 failed because of the differential uptake and binding kinetics of these pH-sensitive dyes.
Using SNARF-calcein we were able to show proliferation to be associated with increased pHi . However, culture conditions were critical for these measurements. Our data indicate that the Na+ /H+ exchanger is involved in this process, since acid load and pHi -recovery experiments showed the alkalization to be amiloride-sensitive. 相似文献
The aim of this study was to investigate whether or not keratinocytes, derived from the BALB/MK cell line, contain a Na
Using SNARF-calcein we were able to show proliferation to be associated with increased pH