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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Newly replicated deoxyribonucleic acid (DNA) in Mycoplasma gallisepticum A5969 is membrane associated. Cells pulse-labeled 1 to 3 min with (3)H-thymidine are lysed by a freeze-thaw procedure. After brief sonic treatment to shear the DNA, differential centrifugation gives a cell fraction (P2) that is enriched sevenfold for pulse-labeled DNA. P2 contains 80% of the total adenosine triphosphatase activity, 65% of the total cholesterol, and morphologically intact terminal bleb structures. Three to four minutes are needed to fully label the DNA growing-point region, whereas 7 to 8 min are required to "chase" 50% of the (3)H-labeled DNA. This pulse-chase removes 80 to 85% of the nascent DNA from the P2 fraction.
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PMID:Membrane association of the deoxyribonucleic acid growing-point region in Mycoplasma gallisepticum. 426 49

The effects of modifications in the cholesterol and fatty acid contents of membranes on the transport of potassium have been studied in Mycoplasma mycoides subspecies capri. A decrease in the cholesterol content from 110 micrograms/mg of membrane protein to less than 10 micrograms/mg of membrane protein is associated with a decrease in the level of intracellular potassium from 40 micrograms of K/mg of protein to 23 micrograms of K/mg of cell protein. Replacement of oleate plus palmitate by elaidate alone in the growth medium has only limited effects on the intracellular K content. In metabolizing cells, 42K influxes were 0.42, 0.65, and 0.69 micrograms of K/mg of cell protein per min for cholesterol-rich cells supplemented with elaidate or with oleate plus palmitate and for cells adapted to low cholesterol and supplemented with elaidate, respectively. This increase in influx was associated with an increase in membrane fluidity as determined by fluorescence polarization experiments in which 1,6-diphenyl-1,3,5-hexatriene was used as a probe. For elaidate-supplemented cells, examination of the temperature dependence of 43K influx revealed the existence of a break or a discontinuity at temperatures corresponding to modifications in the physical state of the membrane. The lack of correspondence between the patterns of K+ influx and the Mg++-adenosine triphosphatase (ATPase) activity indicates that the sensitivity of this influx to the physical state of the membrane is not attributable to the Mg++-ATPase but likely reflects an effect of membrane lipids on the K+ carrier itself.
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PMID:Recent developments in the study of potassium transport in Mycoplasma mycoides subspecies capri. 612 24

Various physiological important activities of Mycoplasma gallisepticum were inhibited by the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline [Cu(DMP)2NO3]. The energy-yielding metabolism was inhibited because the conversion of pyruvate into lactate was found to be blocked by Cu(DMP)2NO3, indicating a selective inhibition of lactate dehydrogenase. Also, the production rate of acetate and the rate of oxygen uptake by whole cells of M. gallisepticum appeared to be strongly decreased. Experiments with crude cell extracts showed an inhibition of reduced nicotinamide adenine dinucleotide (NADH) oxidase by Cu(DMP)2NO3 and an even stronger inhibition of NADH oxidase and lactate dehydrogenase by CuSO4. No preferential inhibition of adenosine 5'-triphosphatase and pyruvate kinase was found. Investigations on the influence of Cu(DMP)2NO3 on deoxyribonucleic acid, ribonucleic acid, and protein synthesis with growing cells of M. gallisepticum showed a selective inhibition of the incorporation of [14C]thymidine into deoxyribonucleic acid. Cu(DMP)2NO3 induced a decrease in the total amount of accessible sulfhydryl groups of whole cells of M. gallisepticum, indicating that the observed diverse toxicity of Cu(DMP)2NO3 may be associated with the interaction of copper ions with protein sulfhydryl groups.
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PMID:Mode of action of the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline on Mycoplasma gallisepticum. 617 82

We have studied the links between the mechanisms of Na(+), K(+) and H(+) movements in glycolysing Mycoplasma mycoides var. Capri cells. In the light of the results reported in the preceding paper [Benyoucef, Rigaud & Leblanc (1982) Biochem. J.208, 529-538], we investigated certain properties of the membrane-bound ATPase of Mycoplasma cells, with special reference to its ionic requirements and sensitivity to specific inhibitors. Our findings show, first, that, although Na(+) stimulated ATPase activity, K(+) did not affect it, and, secondly, that NN'-dicyclocarboidi-imide and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD) were potent inhibitors of the basal ATPase activity, which was unaffected by vanadate and ouabain. We also investigated the movements of Na(+) and H(+) under the experimental conditions applied to the study of the K(+) uptake reported in the preceding paper, and found that when ;Na(+)-loaded cells' previously equilibrated with (22)Na(+) were diluted in a sodium-free medium, addition of glucose induced a rapid efflux of (22)Na(+). This energy-dependent efflux was independent of the presence of KCl in the medium. Studies of the changes in internal pH by 9-aminoacridine fluorescence or [(14)C]methylamine distribution indicated that the movement of Na(+) was coupled to that of protons moving in the opposite direction, a finding that supports the presence of an Na(+)/H(+) antiport. When Na(+)-loaded cells are diluted in an Na(+)-rich medium the Na(+)/H(+) antiport is still active, but cannot decrease the intracellular Na(+) concentration. Under such conditions, net (22)Na(+) extrusion is specifically dependent on the presence of K(+) in the medium. The present results and those derived from the study of K(+) accumulation (the preceding paper) can be rationalized by assuming that Mycoplasma mycoides var. Capri cells contain two transport systems for Na(+) extrusion: an Na(+)/H(+) antiport and an ATP-consuming Na(+)/K(+)-exchange system.
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PMID:Cation transport mechanisms in Mycoplasma mycoides var. Capri cells. The nature of the link between K+ and Na+ transport. 621 66

The results presented show that in Mycoplasma mycoides var. Capri, regulation of glucose uptake by its non-metabolizable analogue methyl alpha-D-glucoside, can be used to control intracellular ATP content. This in turn leads to a control of the rate of proton extrusion catalysed by the Mg2+-dependent ATPase (phi (cHxN)2C H+) and the respective amplitudes of the components of delta mu H+. When Mycoplasma cells are incubated with 10 mM methyl alpha-D-glucoside, the amplitude of phi (cHxN)2C H+, of the electrical potential delta psi and of the chemical gradient delta pH become continuous functions of external glucose concentration within the limits of the non-energized and fully energized states. Analysis of the relationships between graduated amplitudes of delta psi, delta pH and phi (cHxN) 2C H+ show that the primary form of energy stored by a delta mu H+ generator is the electrical potential.
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PMID:Gradation of the magnitude of the electrochemical proton gradient in Mycoplasma cells. 626 Apr 82

Attachment values of Mycoplasma pneumoniae to glass are normally very low when tested in buffer containing bovine serum albumin (10 mg/ml). However, the addition of one of the metabolizable sugars glucose, fructose, or mannose increased attachment more than 10-fold. The effect was dose dependent with a distinct optimum at about 0.25 mg/ml. Higher concentrations reduced this effect. Not only the sugars themselves but also the products of their catabolism, pyruvate and phosphoenolpyruvate, enhanced attachment. Pyruvate was effective in the same range of concentrations as the sugars, whereas phosphoenolpyruvate enhanced attachment at a significantly lower concentration (0.001 mg/ml). Higher levels of these substances also resulted in a decrease of attachment. The glucose-induced increase could be partially inhibited by glucose analogs, especially by 3-O-methyl-glucopyranoside, and by various inhibitors or glycolysis. Furthermore, attachment was strongly reduced by the uncoupling agents carbonylcyanide m-chlorophenylhydrazone and 2,4-dinitrophenol, as well as by dicyclohexylcarbodiimide, an inhibitor of the membrane-bound Mg2+-adenosine triphosphatase, whereas the ionophore valinomycin increased attachment by about 30%. These findings provide strong evidence for coupling between the attachment process of M. pneumoniae to glass and the utilization of metabolic energy.
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PMID:Role of energy metabolism in Mycoplasma pneumoniae attachment to glass surfaces. 678 36

A simple procedure was devised to prepared membranes from Mycoplasma gallisepticum cells. The cells were lysed in an isosmotic NaCl solution by dicyclohexylcarbodiimide, which blocks ATPase activity and interferes with the regulation of cell volume. The procedure can be used to isolate membranes of other osmotically resistant mycoplasmas.
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PMID:Isolation of mycoplasma membranes by dicyclohexylcarbodiimide-induced lysis. 706 81

Fluorescence polarization and ESR experiments using various probes demonstrated that addition of glucose to resting Mycoplasma capricolum and Mycoplasma mycoides subs capri had, if any, a very limited effect on the physical state of their membrane lipids. Under the same conditions the degree of exposure of primary amino groups of membrane proteins to the aqueous surrounding, estimated from fluorescence labeling by fluorescamine and the cycloheptaamylose-fluorescamine complex was significantly increased. This energy dependent increase was blocked by dicyclohexylcarbodiimide (DCCD), an inhibitor of the membrane bound Mg2+ stimulated ATPase of mycoplasma and by carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) which, in mycoplasma, only affects the chemical component of the proton-motive force. Variations in the proton activity gradient across the membrane induced by changing the pH of the labeling medium resulted in parallel variations in the ratio of relative intensities of labeling of energized to resting cells. The values taken by this ratio were up to two for a maximal proton gradient of 0.9 pH unit and tended to unity when the intracellular and extracellular pH tended to equalize. It is concluded that, upon mycoplasma cell energization, membrane proteins undergo a conformational change resulting in the exposure of new free amino groups. This conformational change is primarily dependent on the existence of a delta ph across the membrane and occurs in the absence of important modifications in the physical state of membrane lipids.
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PMID:Effects of energization on membrane organization in mycoplasma. 709 58

The electrochemical proton gradient across mycoplasmal membranes was studied. The transmembrane proton-motive potential, delta p, is composed of two parameters, a transmembrane electric potential difference, delta psi, and a transmembrane proton gradient, delta pH, according to the formula delta p = delta psi -(A x delta pH). Membrane potentials were determined with use of potential-sensitive cyanine dyes. The delta psi for both Mycoplasma mycoides subspecies capri and Mycoplasma gallisepticum was -48 mV +/- 10%, with the inside negative; the delta psi of Acholeplasma laidlawii was -28mV +/- 20%. The delta pH was determined by measuring the distribution of [14C]5,5-dimethyl oxazolidine-2,4-dione between the intracellular space and the medium. The intracellular pH of glycolyzing mycoplasmas was generally more alkaline than the extracellular medium: at an external pH of 7.0, the internal pH was 7.4 and hence delta pH = 0.4, a value corresponding to -24 mV. Thus, the delta p of both M. mycoides subspecies capri and M. gallisepticum was calculated to be -72 mV and that of A. laidlawii, to be -52 mV. The data further indicate that the delta p is generated by a membrane-bound electrogenic, proton-translocating adenosine triphosphatase that operates in the direction of hydrolysis of adenosine triphosphatase, which formed by glycolysis, and leads to proton extrusion.
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PMID:The electrochemical potential across mycoplasmal membranes. 712 58

To sequence the entire 800 kilobase pair genome of the bacterium Mycoplasma pneumoniae, a plasmid library was established with contained the majority of the EcoR1 fragments from M.pneumoniae. The EcoR1 fragments were subcloned from an ordered cosmid library comprising the complete M.pneumoniae genome. Individual plasmid clones were sequenced in an ordered fashion mainly by primer walking. We report here the initial results from the sequence analysis of -56 kb comprising the dnaA region as a potential origin of replication, the ATPase operon and a region coding for a cluster of ribosomal protein genes. The data were compared with the corresponding genes/operons from Bacillus subtilis, Escherichia coli, Mycoplasma capricolum and Mycoplasma gallisepticum.
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PMID:Sequence analysis of 56 kb from the genome of the bacterium Mycoplasma pneumoniae comprising the dnaA region, the atp operon and a cluster of ribosomal protein genes. 860 3


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