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1.
Phillipe L. Janssens de Varebeke 《Phytochemistry》1975,14(10):2153-2155
The ability of putrescine, spermidine and spermine to replace Mg2+ ions in the charging reaction of tRNA was estimated for seventeen amino acids. The polyamines promoted only the transfer reaction in the case of Leu, Ile, Val, Tyr and Arg. A synergistic effect was observed when spermine was added to a suboptimal concentration of Mg2+ (charging at only 5% of the optimal level). This synergistic effect was not observed for Ala, Asp-NH2, His, Lys and Ser. Kinetic studies showed a slower aminoacylation rate in those experiments when spermine and Mg+2 (at 5% of the Mg2+ optimal concn) were used together than with Mg2+ (at the optimal concn) alone. 相似文献
2.
Roger J. Romani Bonita V. Sproule Irvin J. Mettler Sue E. Tuskes 《Phytochemistry》1975,14(12):2563-2567
Readily measurable yields of undamaged tRNA were obtained from tomato, pear and apple fruits by phenolic extraction at pH 8.8, removal of interfering alcohol insoluble substances by precipitation with 0·2 volumes of iso-PrOH and final purification by DEAE chromatography. Various other commonly used extraction and purification procedures were tested and found to be less effective. Active synthetases were isolated from acidic fruit tissues by adequate control of pH and maceration in the frozen state. After acylation with a radioactively labelled amino acid, fruit isoacceptor tRNA species were separated by reverse phase chromatography. 相似文献
3.
Partially purified preparations of Phe- and Tyr-tRNA synthetases were obtained from seed or seedlings of Phaseolus aureus, Delonix regia and Caesalpinia tinctoria, and the ability of a variety of structural analogues of Phe or Tyr to act as alternative substrates or inhibitors was tested. 3-Hydroxymethylphenylalanine, a natural product of C. tinctoria, formed a particularly effective substrate for the Tyr-tRNA synthetase from P. aureus. The structural features commensurate with substrate activity in an analogue molecule are discussed. 相似文献
4.
AspNH2-, Asp- and GluNH2-tRNA synthetases were purified from Phaseolus aureus; their optimum assay conditions, substrate specificities and salt sensitivities were investigated. AspNH2-tRNA synthetase from β-cyanoalanine-producing (Vicia sativa), and non-producing (P. aureus and V. faba) species was able to utilize the analogue as a substrate irrespective of the source of the enzyme. Asp-tRNA synthetase from P. aureus was able to utilize α-aminomalonate and threo-β-hydroxy Asp as a substrate. The transfer of 14C-GluNH2 to tRNA, catalyzed by GluNH2-tRNA synthetase, was only inhibited by high concentrations of those analogues tested; albizziine was the most efficient, but no difference could be demonstrated between the substrate specificities of the enzyme isolated from an albizziine-producer (A. julibrissin and a non-producer (P. aureus) species. 相似文献
5.
Changes in the activity of aminoacyl tRNA synthetases during growth of tobacco XD cells in suspension culture have been determined by the pyrophosphate exchange assay. Alanyl, arginyl, glutamyl, glutaminyl and seryl tRNA synthetases showed the lowest activity, whilst lysyl, histidyl, leucyl, isoleucyl, phenylalanyl threonyl and valyl tRNA synthetases were most active. Most synthetases, and total protein, increased to a maximum, at around 7 days, just before mid-exponential phase, and then fell. 相似文献
6.
Several aminoacyl-tRNA synthetases from the yellow lupin (Lupinus luteus) were stabilized against inactivation during storage at 0–4°, by entrapment in Sephadex or Biogel matrices and drying over P2O5. The degree of stabilization depended on the rate of drying of the gel and the pH of the medium and to a lesser extent on the ionic strength and protein concentration. With the exception of prolyl-tRNA synthetase, a greater stability was achieved with those enzymes which were relatively stable to thermal denaturation. Aminoacyl-tRNA synthetases for glutamic acid, glutamine, methionine and arginine, which become inactivated during purification, were considerably stabilized by this procedure. 相似文献
7.
Inhibition of the k-stimulated ATPase of the plasmalemma of pinto bean leaves by ozone 总被引:9,自引:3,他引:6
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Three varieties of Phaseolus vulgaris which differ in their sensitivity to ozone were examined for changes in some physiological and structural plasma membrane characteristics. Plasma membrane vesicles were prepared from control and ozone-treated (0.2 to 0.5 microliters per liter ozone for 5 hours) leaf tissue, and the (K+ + Mg2+)-ATPase activity determined and compared. No major changes were observed in the resistant varieties. The sensitive variety showed a severe inhibition of ATPase activity which was largely due to a decrease in the K+-stimulated component. This inhibition was completely reversed by the addition of sulfhydryl compounds.
Ozone-induced plasma membrane permeability changes may be effected by damage to membrane proteins, perhaps by oxidation of amino acid sulfhydryl groups to disulfide and sulfenic moieties.
相似文献8.
A readily assayed H+ efflux from sycamore (Acer pseudoplatanus), rye (Lolium perenne), and bean (Phaseolus vulgaris cultivars Red Kidney and Small White) suspension-cultured cells has been detected and partially characterized. The H+ efflux has been shown to require a source of energy, to be significantly stimulated by Na+ and Mg2+ but not by K+ and Ca2+, and to have a pH optimum at 7. The study of this H+ efflux was undertaken because the characteristics of auxin-induced growth and of H+-induced growth are sufficiently similar to suggest that a H+ efflux may be an intermediate in the mechanism of auxin-induced growth. However, the H+ efflux from these suspension-cultured cells was found to be insensitive to exogenously added hormones. 相似文献
9.
Prolyl-tRNA synthetase from plants (e.g. Delonix regia) containing azetidine-2-carboxylic acid (A2C), activated imino acid analogues larger than proline (Pro) more efficiently than did the enzyme from plants lacking A2C. The reverse situation was observed for analogues, including A2C itself, that are smaller than Pro. The enzyme from A2C-producing species was quite labile and salt-sensitive, with a high pH optima for the ATP-32PPi exchange reaction, whereas the enzyme from non-producer species was stable and insensitive to salts, with a lower pH optimum. Certain analogues of Pro, which failed to stimulate ATP-32PPi in the presence of a particular type of Pro-tRNA synthetase, nevertheless could bind to the enzyme and inhibit the esterification of tRNA by Pro. In the absence of tRNA, no significant ATP-32PPi exchange was catalyzed by the Delonix enzyme on addition of A2C; the addition of tRNA resulted in a low but real level of activation of the analogue relative to Pro. These findings are discussed in relation to the ability of the enzyme from A2C-producing plants to discriminate against the analogue. 相似文献
10.
(H+ + K+)-ATPase-enriched membranes were prepared from hog gastric mucosa by sucrose gradient centrifugation. These membranes contained Mg2+-ATPase and p-nitrophenylphosphatase activities (68 ± 9 μmol Pi and 2.9 ± 0.6 μmol p-nitrophenol/mg protein per h) which were insensitive to ouabain and markedly stimulated by 20 mM KCl (respectively, 2.2- and 14.8-fold). Furthermore, the membranes autophosphorylated in the absence of K+ (up to 0.69 ± 0.09 nmol Pi incorporated/mg protein) and dephosphorylated by 85% in the presence of this ion. Membrane proteins were extracted by 1–2% (w/v) n-octylglucoside into a soluble form, i.e., which did not sediment in a 100 000 × g × 1 h centrifugation. This soluble form precipitated upon further dilution in detergent-free buffer. Extracted ATPase represented 32% (soluble form) and 68% (precipitated) of native enzyme and it displayed the same characteristic properties in terms of K+-stimulated ATPase and p-nitrophenylphosphatase activities and K+-sensitive phosphorylation: Mg2+-ATPase (μmol Pi/mg protein per h) 32 ± 9 (basal) and 86 ± 20 (K+-stimulated); Mg2+-p-nitrophenylphosphatase (μmol p-nitrophenol/mg protein per h) 2.6 ± 0.5 (basal) and 22.2 ± 3.2 (K+-stimulated); Mg2+-phosphorylation (nmol Pi/mg protein) 0.214 ± 0.041 (basal) and 0.057 ± 0.004 (in the presence of K+). In glycerol gradient centrifugation, extracted enzyme equilibrated as a single peak corresponding to an apparent 390 000 molecular weight. These findings provide the first evidence for the solubilization of (H+ + K+)-ATPase in a still active structure. 相似文献
11.
BENJAMIN JACOBY 《Physiologia plantarum》1975,35(1):1-4
The light-stimulated absorption of 86Rb+ by Phaseolus vulgaris L. leaf slices was found to be sensitive to dichlorophenyldimethylurea in air as well as in nitrogen, whereas light-stimulated 22Na+ absorption in nitrogen was not sensitive to this inhibitor. The absorption of 22Na+ is not affected by light in air. The absorption of 42K+ is enhanced by a dichlorophenyldimethylurea-insensitive light effect under anaerobic conditions and further increased by light in the absence of the inhibitor. Light-enhanced 42K+ absorption in air was also inhibited by dichlorophenyldimethylurea. Previous work showed that light-stimulated 86Rb+ and 42K+ absorption by Phaseolus vulgaris leaf slices is restricted to the guard cells. The present results are discussed with reference to the effect of light on stomatal opening. 相似文献
12.
The adenosine triphosphatase (ATPase) system in worker honey-bee brains showed an increased activity of 57 per cent in Na+K+ATPase and 63 per cent in Mg2+ATPase from adult emergence to 7 days post-emergence. Mg2+ATPase activity remained about the same throughout the remainder of adult life, while Na+K+ATPase remained the same until the sixth week, when a decline occurred. The percentage mortality of the bees exceeded 90 per cent at the time of decline of Na+K+ATPase. The in vitro inhibition of Mg2+ATPase and Na+K+ATPase by 10 μM DDT was between 40 and 50 per cent and about 20 per cent, respectively. A somewhat greater sensitivity to DDT was determined in brains of older honey-bees. 相似文献
13.
The dynamics of Na+, K+, and proline accumulation in various organs of non nodulated Vigna sinensis and Phaseolus aureus was followed during their acclimation to two levels of salinities for a period of 35 days and was correlated to the vegetative growth of the two species. The rate of Na+ and K+ absorption is at a maximum during the first 15 to 20 days of culture. K+ absorption is not completely inhibited even at 100 mM NaCl although the endogenous Na+ largely surpasses that of K+ in certain organs. Low salinity rather accelerates K+ absorption in both species. The relative growth rates (RGR) correlate with the rate of Na+ and K+ accumulation. At low salinity (10 mM NaCl), the RGR of V. sinensis is greater than that of P. aureus. However, at high salinity (100 mM NaCl) the RGR is the same for both species. The growth of the younger parts of the two species is not arrested by salt treatment. Very high accumulation of Na+ is avoided in organs with less vacuolated tissues. At no time does the endogenous K : Na ratio in these organs fall below 1.0. Certain organs, especially the roots, hypocotyls, and the lower parts of the stems are capable of storing large quantities of Na+. In V. sinensis, the accumulated Na+ and K+ are evenly distributed among the various organs while in P. aureus they are rather concentrated in the roots. External salinity creates water deficiency in the younger plant parts and as a consequence, proline accumulates especially in the youngest aerial organs - more in P. aureus than in V. sinensis. The accumulation of this amino acid in both the species is dependent on time and correlates directly, not only with the water deficit, but also with the K+ contents. In contrast, it does not seem to depend directly on the endogenous Na+ content. The relative salt tolerance of the two species and the possible role of K+, Na+ and proline in the osmotic adjustments of the two species under saline conditions are discussed. 相似文献
14.
A Study of the Aminoacyl-sRNA Synthetases of Phaseolus vulgaris in Relation to Germination 总被引:3,自引:2,他引:1
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Optimum conditions for the extraction and assay by ATP-pyrophosphate exchange of the aminoacyl-sRNA synthetases of the various tissues of french bean (Phaseolus vulgaris) seeds and seedlings are described. Extracts of plumules, after passage through Sephadex G-25, were assayed for synthetase activity using an amino acid mixture as substrate, when a 30 to 100-fold stimulation of exchange above the endogenous level was obtained. This marked enhancement of exchange by added amino acids is largely attributed to the use of dilute extracts. 相似文献
15.
Pro-tRNA synthetase from Phaseolus aureus was photoinactivated in the presence of methylene blue or rose bengal. Pro and several imino acid analogues protected the enzyme against dye-mediated photoinactivation but ATP was ineffective. Together with kinetic data, this evidence suggested that a His-residue near the Pro-binding site was involved in the enzyme reaction. In the absence of methylene blue, Phaseolus enzyme was stable to light whilst that from Delonix was rapidly and reversibly photoinactivated. ATP as well as Pro, protected the Delonix enzyme against dye-independent photoinactivation. In the presence of methylene blue, the Delonix enzyme was more rapidly photoinactivated than in the absence of the dye. p-Chloromercuribenzoate (pCMB)-inhibited enzyme from both Phaseolus and Delonix was reactivated by sulphydryl reducing reagents. Reactivation of Delonix enzyme was markedly temperature-dependent whilst Phaseolus enzyme was reactivated equally efficiently at all temperatures tested. ATP, tRNA, Pro and several analogues of Pro, protected both the Phaseolus and Delonix enzymes against pCMB inhibition. The possible roles of the His-residue and SH group are discussed in relation to the known differences in substrate specificity between the Phaseolus and Delonix enzymes. 相似文献
16.
Binding of Sr2+ to bean mitochondria (Phaseolus vulgaris) shows a dissociation constant of 25 × 10−6 and results in 40 to 50 nmoles of Sr2+ bound per mg protein. The binding is partially inhibited by valinomycin plus K+, 2, 4-dinitrophenol, as well as ruthenium red at a level of the 120 nmoles per mg protein. These compounds also partially inhibit active uptake of Sr2+. Calcium and Mg2+ also partially inhibit binding in the same magnitude as previously reported for inhibition of transport. Phosphate which is required for divalent cation transport is without effect on the binding of Sr2+. The possible role of the observed binding sites in divalent cation transport is discussed. 相似文献
17.
The unidirectional influx of methionine into the brush border epithelium of chicken jejunum has been studied. Tissues leached of Na+ transport methionine from a medium devoid of Na+ with reduced apparent affinity (Kt) and maximal flux (Jmax). Addition of Na+ to the medium during a 1-min incubation with substrate, or during a 30-min preincubation, restored Kt but affected Jmax slightly. Theophylline was found to maintain Jmax in the absence of Na+. Essentially complete restoration of Kt and Jmax could be attained when theophylline-treated tissue was exposed to Na+ for 30 min. Influx from a Na+ medium was unaffected by theophylline pretreatment in Na+-containing buffer. Kt was increased without an effet upon Jmax when influx was studied from choline medium following preincubation in Na+.Modifiers of tissue cyclic AMP levels were investigated in conjunction with theophylline. Histamine and carbachol were found to inhibit theophylline-stimulated transport. Secretin was found to stimulate influx in Na+-leached tissue, but did not potentiate the theophylline effect. Amino acids in the incubation medium inhibited theophylline-stimulated influx, whereas preloaded lysine or methionine had no effect.The results are interpreted in terms of a model which envisions roles for cellular and external Na+ and for cyclic AMP in the activation and regulation of amino acid transport in intestine. 相似文献
18.
19.
Role of Cations in Accumulation and Release of Phosphate by Acinetobacter Strain 210A 总被引:3,自引:2,他引:1
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Johan W. van Groenestijn Gerard J. F. M. Vlekke Dsire M. E. Anink Maria H. Deinema Alexander J. B. Zehnder 《Applied microbiology》1988,54(12):2894-2901
Cells of the strictly aerobic Acinetobacter strain 210A, containing aerobically large amounts of polyphosphate (100 mg of phosphorus per g [dry weight] of biomass), released in the absence of oxygen 1.49 mmol of Pi, 0.77 meq of Mg2+, 0.48 meq of K+, 0.02 meq of Ca2+, and 0.14 meq of NH4+ per g (dry weight) of biomass. The drop in pH during this anaerobic phase was caused by the release of 1.8 protons per PO43− molecule. Cells of Acinetobacter strain 132, which do not accumulate polyphosphate aerobically, released only 0.33 mmol of Pi and 0.13 meq of Mg2+ per g (dry weight) of biomass but released K+ in amounts comparable to those released by strain 210A. Stationary-phase cultures of Acinetobacter strain 210A, in which polyphosphate could not be detected by Neisser staining, aerobically took up phosphate simultaneously with Mg2+, the most important counterion in polyphosphate. In the absence of dissolved phosphate in the medium, no Mg2+ was taken up. Cells containing polyphosphate granules were able to grow in a Mg-free medium, whereas cells without these granules were not. Mg2+ was not essential as a counterion because it could be replaced by Ca2+. The presence of small amounts of K+ was essential for polyphosphate formation in cells of strain 210A. During continuous cultivation under K+ limitation, cells of Acinetobacter strain 210A contained only 14 mg of phosphorus per g (dry weight) of biomass, whereas this element was accumulated in amounts of 59 mg/g under substrate limitation and 41 mg/g under Mg2+ limitation. For phosphate uptake in activated sludge, the presence of K+ seemed to be crucial. 相似文献
20.
Rates of 14C-photosynthate unloading from excised seed-coathalves of Phaseolus vulgaris L. plants were stimulated by externalKCI concentrations in excess of 10 mM with an optimal responseat 100150 mM KCI. The cellular pattern of 14C-photosynthatemetabolism was not altered by KCI but the treatment preferentiallystimulated the release of sucrose from the seed-coats. Photosynthateunloading was insensitive to Cl and was stimulated bya range of membrane-permeable cations (Na+, Mg2+ and tetraphenylphosphoniumion) in addition to K+. The K+ ionophore, valinomycin, abolishedthe K+ stimulation of 14C-photosynthate unloading. A switchto a wash solution containing K+ elicited a rapid burst of 14C-photosynthateunloading; the rate constant for the final phase of 14C-efflux(probably across the tonoplast) was unaffected by K+. The KCItreatment did not change the passive permeability of eitherthe plasmalemma or tonoplast. While sucrose influx across theplasmalemma was insensitive to K+, sucrose transfer to the vacuolewas slowed. The results obtained support the postulate thatK+ (and other membrane permeable cations) preferentially stimulatesucrose efflux across the plasmalemma of the unloading cellsby serving to carry positive charge in the opposite direction. Phaseolus vulgaris, bean, photosynthate unloading, potassium stimulation, seed-coat 相似文献