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1.
Tjakko Abee Jan Knol Klaas J. Hellingwerf Evert P. Bakker Annette Siebers Wil N. Konings 《Archives of microbiology》1992,158(5):374-380
Cells of the purple non-sulphur bacterium Rhodobacter sphaeroides express a high-affinity K+ uptake system when grown in media with low K+ concentrations. Antibodies againts the catalytic KdpB protein or the whole KdpABC complex of Escherichia coli crossreact with a 70.0 kDa R. sphaeroides protein that was expressed only in cells grown in media with low K+ concentrations. In membranes derived from R. sphaeroides cells grown with low K+ concentrations (induced cells), a high ATPase activity could be detected when assayed in Tris-HCl pH 8.0 containing 1 mM MgSO4. This ATPase activity increased upon addition of 1 mM KCl from 166 to 289 mol ATP hydrolysed x min-1 x g protein-1 (1.7-fold stimulation). The K+-stimulated ATPase activity was inhibited approximately 93% by 0.5 mM vanadate but hardly by N,N-dicyclohexylcarbo-diimide (DCCD). These results indicate that the inducible K+-ATPase in R. sphaeroides resembles the Kdp K+-translocating ATPase of Escherichia coli. This Kdp-like transport system is also expressed in R. capsulatus and Rhodospirillum rubrum during growth in media with low K+ concentrations suggesting a wide distribution of this transport system among phototrophic bacteria.Abbreviations
electrical potential difference across the cytoplasmic membrane
- pH
pH difference across the cytoplasmic membrane
- BSA
bovine serum albumine
- PAGE
polyacrylamide gel electrophoresis
- HEPES
4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid
- PMSF
phenyl-methyl-sulfonyl fluoride
- DCCD
N,N-dicyclohexylcarbodiimide
- AIB
2--aminoisobutyric acid
- TMG
methyl--d-thiogalactopyranoside 相似文献
2.
From genomic libraries of the purple non-sulfur bacteria Rhodospirillum rubrum Ha and Rhodobacter sphaeroides ATCC 17023 in the broad-host range cosmid pVK100, we cloned a 15- and a 14-kbp HindIII restriction fragment, respectively. Each of these fragments restored the ability to accumulate poly(3-hydroxybutyrate) (PHB), in the PHB-negative mutant Alcaligenes eutrophus PHB-4. These hybrid cosmids also complemented PHB-negative mutants derived from wild-type R. rubrum or R. sphaeroides. Both fragments hybridized with the PHB synthase structural gene of A. eutrophus H16 and conferred the ability to express PHB synthase activity. Only the 15-kbp HindIII fragment from R. rubrum conferred on the mutant PHB-4 the ability to form large PHB granules (length up to 3.5 microns). 相似文献
3.
4.
The strictly anaerobic homoacetogenic bacteria Acetobacterium woodii and Sporomusa sphaeroides differ with respect to their energy metabolism. Since growth as well as acetate and ATP formation of A. woodii is strictly dependent on Na+, but that of S. sphaeroides is not, the question arose whether these organisms also use different coupling ions for mechanical work, i.e. flagellar rotation.
During growth on fructose in the presence of Na+ (50 mM), cells of A. woodii were vigorously motile, as judged by light microscopy. At low Na+ concentrations (0.3 mM), the growth rate decreased by only 15%, but the cells were completely non-motile. Addition of Na+ to such cultures restored motility instantaneously. Motility, as determined in swarm agar tubes, was strictly dependent on
Na+; Li+, but not K+ partly substituted for Na+. Of the amilorides tested, phenamil proved to be a specific inhibitor of the flagellar motor of A. woodii. Growth and motility of S. sphaeroides was neither dependent on Na+ nor inhibited by amiloride derivatives. These results indicate that flagellar rotation is driven by ΔμNa
+ in A. woodii, but by ΔμH
+ in S. sphaeroides.
Received: 30 May 1995 / Accepted: 31 August 1995 相似文献
5.
The electron-transfer reactions and thermodynamic equilibria involving the quinone acceptor complex in bacterial reaction centers from R. sphaeroides were investigated. The reactions are described by the scheme: We found that the charge recombination pathway of D+QAQ?B proceeds via the intermediate state D+Q?AQB, the direct pathway contributing less than approx. 5% to the observed recombination rate. The method used to obtain this result was based on a comparison of the kinetics predicted for the indirect pathway (given by the product kAD-times the fraction of reaction centers in the Q?AQB state) with the observed recombination rate, kobsD+ →D. The kinetic measurements were used to obtain the pH dependence (6.1 ? pH ? 11.7) of the free energy difference between the states Q?AQB and QAQ?B. At low pH (less than 9) QAQ?B is stabilized relative to Q?AQB by 67 meV, whereas at high pH Q?AQB is energetically favored. Both Q?A and Q?B associate with a proton, with pK values of 9.8 and 11.3, respectively. The stronger interaction of the proton with Q?B provides the driving force for the forward electron transfer. 相似文献
6.
7.
Resonance Raman spectra of the π-cation of bacterio-chlorophyll a in solution at 30 K are reported and discussed. Outer CC bonds of the pyrroles and the methine bridges are weakened by the ionization, while CN and Mg-N bonds remain essentially unaffected. Resonance Raman spectra of reaction centers suggest that the positive charge on P-870+ should be localized on a single bacteriochlorophyll molecule by the lifetime of the scattering process (≈ 10?13 s). 相似文献
8.
(1) Current models for the mechanism of cyclic electron transport in Rhodopseudomonas sphaeroides and Rhodopseudomonas capsulata have been investigated by observing the kinetics of electron transport in the presence of inhibitors, or in photosynthetically incompetent mutant strains. (2) In addition to its well-characterized effect on the Rieske-type iron sulfur center, 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole (UHDBT) inhibits both cytochrome b50 and cytochrome b?90 reduction induced by flash excitation in Rps. sphaeroides and Rps. capsulata. The concentration dependency of the inhibition in the presence of antimycin (approx. 2.7 mol UHDBT/mol reaction center for 50% inhibition of extent) is very similar to that of its inhibition of the antimycin-insensitive phase of ferricytochrome c re-reduction. UHDBT did not inhibit electron transfer between the reduced primary acceptor ubiquinone (Q?I) and the secondary acceptor ubiquinone (QII) of the reaction center acceptor complex. A mutant of Rps. capsulata, strain R126, lacked both the UHDBT and antimycin-sensitive phases of cytochrome c re-reduction, and ferricytochrome b50 reduction on flash excitation. (3) In the presence of antimycin, the initial rate of cytochrome b50 reduction increased about 10-fold as the Eh(7.0) was lowered below 180 mV. A plot of the rate at the fastest point in each trace against redox potential resembles the Nernst plot for a two-electron carrier with Em(7.0) ≈ 125 ± 15 mV. Following flash excitation there was a lag of 100–500 μs before cytochrome b50 reduction began. However, there was a considerably longer lag before significant reduction of cytochrome c by the antimycin-sensitive pathway occurred. (4) The herbicide ametryne inhibited electron transfer between Q?I and QII. It was an effective inhibitor of cytochrome b50 photoreduction at Eh(7.0) 390 mV, but not at Eh(7.0) 100 mV. At the latter Eh, low concentrations of ametryne inhibited turnover after one flash in only half of the photochemical reaction centers. By analogy with the response to o-phenanthroline, it is suggested that ametryne is ineffective at inhibiting electron transfer from Q?I to the secondary acceptor ubiquinone when the latter is reduced to the semiquinone form before excitation. (5) At Eh(7.0) > 200 mV, antimycin had a marked effect on the cytochrome b50 reduction-oxidation kinetics but not on the cytochrome c and reaction center changes or the slow phase III of the electrochromic carotenoid change on a 10-ms time scale. This observation appears to rule out a mechanism in which cytochrome b50 oxidation is obligatorily and kinetically linked to the antimycin-sensitive phase of cytochrome c reduction in a reaction involving transmembrane charge transfer at high Eh values. However, at lower redox potentials, cytochrome b50 oxidation is more rapid, and may be linked to the antimycin-sensitive reduction of cytochrome c. (6) It is concluded that neither a simple linear scheme nor a simple Q-cycle model can account adequately for all the observations. Future models will have to take account of a possible heterogeneity of redox chains resulting from the two-electron gate at the level of the secondary quinone, and of the involvement of cytochrome b?90 in the rapid reactions of the cyclic electron transfer chain 相似文献
9.
Reaction centres from Rhodopseudomonas sphaeroides, strain R-26, have been solubilised in hexane by the use of phospholipids and cations. Two procedures have been developed: (I) a two-step technique involving the formation of detergent-free proteoliposomes from detergent solubilised reaction centres and phospholipids and mixing these with hexane in the presence of cations; (II) directly sonicating detergent-solubilised reaction centres with phosopholipids before mixing with hexane and cations.The yield of the extracted complex varied with the ratios of protein, phospholipid and cations, species of phospholipid, and sonication time. The spectral characteristics of the complex in the organic phase were similar to those of detergent-solubilised reaction centres. The stability of the reaction centres appeared to be dependent on the presence of phospholipid and water in the hexane. The usefulness of the hexane solution as a model membrane system is discussed and its possible future applications are considered. 相似文献
10.
(1) Three analogs of merocyanine dyes added to suspensions of chromatophore vesicles showed absorbance changes responding to the change in surface potential induced by salt addition and to the change in membrane potential induced by illumination. (2) The extent of the light-induced absorbance changes of the dyes was linearly related, in the presence and absence of uncouplers, to that of carotenoid spectral shift which is an intrinsic probe of the intramembrane electric field. (3) Comparison of the merocyanine absorbance changes induced by salt addition with those induced by illumination indicated that the surface potential change in the outer surface of chromatophore membranes during illumination was very small. (4) Judging from the spectra of these absorbance and from the low permeabilities of the dyes to membrane, the absorbance change are attributed to change in distribution of the dyes between the medium and the outer surface region in chromatophore membranes. The extent of the light-induced absorbance changes of merocyanine dyes depended on the salt concentration of the medium. The types of dependence were different among three merocyanine analogs. This is explained by the mechanism mentioned above assuming appropriate parameters. It is suggested that, under continuous illumination, an equilibrium of the electrochemical potential of H+ is reached between the bulk aqueous phase and the outer surface region in the membrane where the merocyanine dyes are distributed. 相似文献