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At least 19 recordsLinked to original sources
PubMed1978

Proteins exposed at the surface of chromatophores of Rhodospirillum rubrum: the orientation of isolated chromatophores.

The exposure of proteins at the surface of isolated chromatophores (i.e., the cytoplasmic face of intracytoplasmic membranes) of Rhodospirillum rubrum was studied by proteolysis as well as by enzymatic iodination with 125I. Analyses were performed after polyacrylamide gel electrophoresis of chromatophore proteins solubilized with sodium dodecyl sulfate. Reversible light induced proton uptake by partially digested chromatophores was used as a criterion for the integrity of the permeability barrier and thus, as evidence for proteolysis only of proteins outside of this barrier. Trypsin or alpha-chymotrypsin completely cleaved four proteins which were identified as the heavy subunit of succinate dehydrogenase (Mr = 64 000), the alpha- and beta-subunits of coupling factor ATPase (Mr = 55 000 and 51 000), and the heavy (H) subunit of photochemical reaction centers (Mr = 31 000). alpha-Chymotrypsin, in addition, attacked the protein (Mr = 9000) of light harvesting bacteriochlorophyll preparations. By enzymatic iodination, the same proteins were labeled as were digested with trypsin or alpha-chymotrypsin except for the protein of Mr = 9000. In addition, significant label was incorporated into three more proteins, one of which (Mr = 41 000) could be identified as a major protein of the cell wall. The complete cleavage with trypsin of four proteins exposed at the surface indicated that isolated chromatophores were homogeneously oriented regardless of the method employed for cell breakage, i.e., passage through a French pressure cell at different forces or osmotic shock of sphaeroplasts.

Bacterial Chromatophores↗
PubMed1976

Membranes of Rhodospirillum rubrum: physicochemical properties of chromatophore fractions isolated from osmotically and mechanically disrupted cells.

Isolation of highly purified membrane fractions from phototrophically grown Rhodospirillum rubrum was achieved by velocity and isopyknic sedimentation under carefully controlled ionic conditions. Bacteriochlorophyll-rich and succinic dehydrogenase-rich chromatophores that were essentially devoid of contamination by non-chromatophore protein were separated from a denser fraction in extracts disrupted in a French pressure cell. Highly purified chromatophores and a nearly photopigment-free envelope fraction were also obtained from cells lysed by treatment with ethylenediaminetetraacetate-lysozyme-Brij 58. After lysis with lysozyme and ethylenediaminetetraacetate alone, about 50% of the total photosynthetic pigment was released in chromatophores similar to those isolated by the above procedures. Chromatophores prepared by each method were found to have very similar near-infrared absorption spectra, overall chemical composition, equilibrium buoyant densities in CsCl, and protein patterns in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The protein profiles of the dense, outer membrane-rich fractions were different from those of the chromatophores. The release of much of the photosynthetic apparatus as discrete chromatophores is osmotically lysed extracts necessitates a reevaluation of the concept that isolated chromatophores arise only from mechanical comminution of a larger membrane structure.

Bacterial Chromatophores↗
PubMed1975

Role of ubiquinone-10 in electron transport system of chromatophores from Rhodospirillum rubrum.

The role of ubiquinone-10 in the activities for the reduction of free cytochrome c2 and bound cytochrome cc' by succinate was studied with chromatophores from a blue-green mutant (G-9) of Rhodospirillum rubrum. 1. By a single extraction with isooctane, approximately 90% of ubiquinone-10 was easily removed from the chromatophores. In the extracted chromatophores, the activity for succinate-cytochrome c2 reduction decreased to 5-10% of the original activity. This depressed activity was mostly restored by adding ubiquinone-10. The remaining quinone was hardly extractable, even by repeated extractions. With repeatedly extracted chromatophores, the activity for succinate-cytochrome c2 reduction was mostly restored to the same extent as with once-extracted chromatophores, whereas the extent of inhibtion of the activity by antimycin A gradually fell. 2. In isooctane-extracted chromatophores, the activity for the reduction of bound cytochrome cc' by succinate under anaerobic conditions decreased to 35 to 95% of the original level. With chromatophores in which the remaining activity was as low as 40% of the original level, the activity was partially restored by adding ubiquinone-10, but this was not the case with chromatophores in which the remaining activity was higher than approximately 50% of the original level.

Alkanes↗
PubMed1978

Measurement by a flow dialysis technique of the steady-state proton-motive force in chromatophores from Rhodospirillum rubrum. Comparison with phosphorylation potential.

1. In the light a transmembrane electrical potential of 100 mV has been estimated to occur in chromatophores from Rhodospirillum rubrum. The potential was determined by measuring the steady-state distribution of the permeant SCN- across the chromatophore membrane using a flow dialysis technique. The potential was not observed in the dark, nor in the presence of antimycin. It was dissipated on the addition of carbonyl cyanide p-trifluoromethoxyphenylhydrazone. The potential was reduced by between 15 and 20 mV when ADP and Pi were added. Hydrolysis of ATP by the chromatophores generated a membrane potential of about 80 mV. 2. Using a flow dialysis technique light-dependent uptake of methylamine was observed only in the presence of concentrations of SCN- that were 500-fold higher than were used to measure the membrane potential. It is concluded that the pH gradient across the illuminated chromatophore membrane is insignificant except in the presence of relatively high concentrations of a permeant anion like thiocyanate. Further evidence that a negligible pH gradient was generated by the chromatophores is that addition of K+ and nigericin to illuminated chromatophores did not stimulate uptake of SCN-. 3. In the light of chromatophores established and maintained a phosphorylation potential of up to 14 kcal/mol. If a phosphorylation potential of this magnitude is to be poised against a proton-motive force that comprises solely a membrane potential of approx. 100 mV, then at least five protons must be translocated for each ATP synthesised via a chemiosmotic mechanism.

Adenine Nucleotides↗
PubMed1975

The functional unit of electrical events and phosphorylation in chromatophores from Rhodopseudomonas sphaeroides.

1. From electron micrographs of chromatophores from Rhodopseudomonas spaeroides and from the estimated bacteriochlorophyll per chromatophore was estimated. The mean diameter of the chromatophore vesicles was 600 A. 2. The decay of the flash-induced electric potential across the chromatophore membrane measured by the carotenoid band shift was 20% accelerated by about one valinomycin molecule per 4700 bacteriochlorophyll, i.e. by one ionophore molecule per chromatophore. 3. The inhibition of the flash-induced ATP formation by valinomycin followed a similar pattern to the accelerated decay of the electric potential. 4. The single turnover flash yield of ATP synthesis gave a mean value of one ATP per 1470 bacteriochlorophyll or about 3 ATP per vesicle. 5. With regard to the partitioning of the ionophore between the membrane (85%) and aqueous phase (15%) we conclude that one molecule of valinomycin per chromatophore is sufficient to begin to collapse the electrical potential and inhibit ATP synthesis. It is therefore suggested that the membrane potential is an essential component of the energized state which is used for phosphorylation. The results correspond to those obtained for the 100-fold larger vesicles in chloroplasts (thylakoids) where one molecule of ioophore is also sufficient to quench both events.

Adenosine Triphosphate↗
PubMed1977

Photooxidase system of Rhodospirillum rubrum. I. Photooxidations catalyzed by chromatophores isolated from a mutant deficient in photooxidase activity.

The aerobic photooxidations of reduced 2,6-dichlorophenolindophenol and of reaction-center bacteriochlorophyll (P-870) have been investigated in membrane vesicles (chromatophores) isolated from a non-phototrophic Rhodospirillum rubrum strain. In aerobic suspensions of wild-type chromatophores, continuous light elicits an increase of the levels of 2,6-dichlorophenolindophenol and of oxidized P-870, which reach steady-state values shortly after the onset of illumination. In contrast, light induces in mutant suspensions a transient increase of the levels of 2,6-dichlorophenol-indophenol and of oxidized P-870, which fall to low steady-state values within a few seconds. These observations suggest that the mutation has altered a redox constituent located on the low-potential side of the photochemical reaction center, between a pool of acceptors and oxygen. Since endogenous cyclic photophosphorylation is catalyzed by mutant chromatophores at normal rates, it appears that the constituent altered by the mutation does not belong to the cyclic electron-transfer chain responsible for photophosphorylation. However, the system which mediates the aerobic photooxidations and the cyclic system are not completely independent: endogenous photophosphorylation is inhibited by oxygen in wild-type chromatophores but not in mutant chromatophores; in addition, the inhibitor of cyclic electron flow, 2-heptyl-4-hydroxyquinoline-N-oxide, enhances the aerobic photooxidation of reduced 2,6-dichlorophenolindophenol by chromatophores from both strains. These results support a tentative branched model for light-driven electron transfer. In that model, the constituent altered in the mutant strain is located in a side electron-transfer chain which connects the cyclic acceptors to oxygen.

2,6-Dichloroindophenol↗
PubMed1979

Membranes of Rhodopseudomonas sphaeroides: effect of cerulenin on assembly of chromatophore membrane.

The effects of cerulenin were investigated in Rhodopseudomonas sphaeroides to elucidate further the mechanisms controlling the assembly of the chromatophore membrane. When this potent inhibitor of fatty acid biosynthesis was added to photosynthetically grown cultures, there was an immediate cessation of phospholipid, bacteriochlorophyll a, carotenoid, and ubiquinone formation. Concurrently, there was also a marked decrease in the rate of incorporation of protein into the chromatophore membrane. In contrast, only a small decrease in the rate of soluble and cell envelope protein synthesis was observed and, in chemotrophically grown cells, protein continued to be incorporated into both the cytoplasmic and outer membranes. The removal of delta-aminolaevulinate from mutant H-5 of R. sphaeroides, which requires this porphyrin precursor, was reexamined to determine whether cerulenin-induced cessation of chromatophore protein incorporation was due solely to blocked bacteriochlorophyll a synthesis. In the deprived H-5 cells, inhibition of [35S]methionine incorporation into chromatophores was confined mainly to apoproteins of bacteriochlorophyll a complexes. Other minor chromatophore proteins continued to be inserted to a greater extent than in cerulenin-treated wild type where phospholipid synthesis has also ceased. These results indicated that the assembly of the chromatophore membrane is under strict regulatory control involving concomitant phospholipid, pigment, and protein syntheses.

Aminolevulinic Acid↗
PubMed1976

Generation of electric current by chromatophores of Rhodospirillum rubrum and reconstitution of electrogenic function in subchromatophore pigment-protein complexes.

Lipoprotein complexes, containing (1) bacteriochlorophyll reaction centers, (2) bacteriochlorophyll light-harvesting antenna or (3) both reaction centers and antenna, have been isolated from chromatophores of non-sulphur purple bacteria Rhodospirillum rubrum by detergent treatments. The method of reconstituting the proteoliposomes containing these complexes is described. Being associtated with planas azolectin membrane, ptoteoliposomes as well as intact chromatophores were found to generate a light-dependent transmembrane electric potential difference measured by Ag/AgC1 electrodes and voltmeter. The direction of the electric field inproteoliposomes can be regulated by the addition of antenna complexes to the reconstitution mixture. The reaction center complex proteoliposomes generate an electric field of a direction opposite to that in chromatophores, whereas proteoliposomes containing reaction center complexes and a sufficient amount of antenna complexes produce a potential difference as in chromatophores. ATP and inorganic pyrophosphate, besides light, were shown to be usable as energy sources for electric generation in chromatophores associated with planar membrane.

Bacterial Chromatophores↗
PubMed1977

Light-induced pH changes and changes in absorbance of pH indicators in Rhodospirillum rubrum chromatophores.

1. The light-induced pH change of chromatophore suspensions from Rhodospirillum rubrum was stimulated significantly and similarly by KCl, NaCl, LiCl, RbCl, CsCl, MgCl2, MnCl2, and CaCl2. In the dark, the pH of chromatophore suspensions decreased immediately and markedly on adding these salts. 2. The light-induced pH change stimulated by KCl plus valinomycin was inhibited by LiCl and NaCl, but not by RbCl. 3. The optimum pH values for light-induced pH change and photosynthetic ATP formation were around 5 and 8, respectively. The amount of chromatophore-bound ubiquinone-10 reduced in the light was independent of pH from 5 to 9. At pH 8, the number of protons incorporated into chromatophores in the light was one-half of the number of ubiquinone-10 molecules reduced in the light. 4. Among several pH indicators tested, bromothymol blue (BTB) and neutral red (NR) showed absorbance changes on illumination of chromatophores. Although the pH change indicated by the absorbance change was opposite to the light-induced pH change of the medium, the effect of KCl on the absorbance changes of BTB and NR, and the effect of valinomycin on that of NR, but not on that of BTB, were similar to those on the light-induced pH change. 5. The light-induced absorbance change of BTB was significantly inhibited by NR, whereas that of NR was hardly influenced by BTB. 6. Oligomycin stimulated the light-induced absorbance change of BTB under either non-phosphorylating or phosphorylating conditions. On the other hand, that of NR under phosphorylating conditions was 50% of that under non-phosphorylating conditions, and was increased by oligomycin.

Bacterial Chromatophores↗
PubMed1979

Modifiable chromatophore proteins in photosynthetic bacteria.

The chromatophores of Chromatium vinosum, as well as six other photosynthetic bacteria, contained two or more proteins which were insoluble when heated in the presence of sodium dodecyl sulfate (SDS) and 2-mercaptoethanol (beta-ME). When the chromatophores were dissolved at room temperature in SDS-beta-ME, these proteins were present in the SDS-polyacrylamide gel electrophoresis profiles, but when the samples were dissolved at 100 degrees C, they were absent or considerably diminished. When one-dimensional gels of chromatophores solubilized at room temperature were soaked in the SDS-beta-ME solution and heated to 100 degrees C and the gels were run in a second dimension, the proteins became immobilized in the original first-dimension gel, where they could be detected by staining. The two major proteins so affected in C. vinosum had apparent molecular weights of 28,000 and 21,000. The chromatophores of several other photosynthetic bacteria also contained predominant proteins between 30,000 and 19,000 molecular weight, which became insoluble when heated in the presence of SDS and beta-ME. In at least two of the species examined, these appeared to be reaction center proteins. The conditions causing the proteins to become insoluble were complex and involved temperature, SDS concentration, and the presence of sulfhydryl reagents. The chromatophores of four of the Chromatiaceae species and two strains of one of the Rhodospirillaceae species examined had a protein-pigment complex that was visible in SDS-polyacrylamide gel profiles of samples dissolved at room temperature but was absent in samples dissolved at 100 degrees C.

Bacterial Chromatophores↗
PubMed1975

Postillumination adenosine triphosphate synthesis in Rhodospirillum rubrum chromatophores. I. Conditions for maximal yields.

The very low level of postillumination ATP synthesis in chromatophores was markedly stimulated when permeant anions (thiocyanate or perchlorate) or permeant cations (potassium in the presence of valinomycin) were added to the light stage. Although these compounds stimulated also light-induced proton uptake in chromatophores the pH dependence of both photoreactions was different. Proton uptake peaked at pH 6.5 while the amount of postillumination ATP was maximal when the light stage was carried out around pH 7.7. The increased yield of ATP at the more alkaline pH could not be explained by a slower decay of the high energy state at this pH, since the decay rate was faster at pH 7.7 than at pH 6.5. The proton concentration gradient which is maintained across the chromatophore membrane in the light was also found to increase when the external pH was raised from 6.0 to 8.0. Only a minimal amount of postillumination ATP was formed when this gradient was below 2.1 pH units, but above this value the ATP yield rose steeply as a function of the increasing pH gradient. In light of these results it is suggested that in order to obtain a high yield of postillumination ATP synthesis in chromatophores two conditions are required: the particles have to be loaded with a sufficient number of protons and a light-induced pH gradient above a certain threshold value has to be maintained across their membrane. The low yield of postillumination ATP in chromatophores and the increase obtained by adding permeating ions, is thus explained by similar variations in the extent of the pH gradient, which exceeded the threshold value only in the presence of the permeating ions.

Adenosine Diphosphate↗
PubMed1976

Preparation and properties of bacterial chromatophores entrapped in polyacrylamide.

The immobilization of Rhodospirillum rubrum chromatophores was successfully performed by entrapping them in polyacrylamide. Their photophosphorylating activity was about 40% of native chromatophores. The temperature and pH optima for immobilized chromatophores were similar to the native photosynthetic apparatus and kinetic parameters showed that the rate of photophosphorylation in polyacrylamide particles was diffusion controlled. Light penetration of the gel particles was not a limiting parameter. Immobilization considerably increased the stability of the chromatophores towards denaturation.

Acrylamides↗
PubMed1975

A large photoreactive particle from Chromatium vinosum chromatophores.

Large photoreactive particles from Chromatium vinosum are obtained pure and in high yield by using a mixture of detergents at high ionic strength to dissociate the chromatophore membrane. The particles contain all of the secondary electron acceptor of the chromatophores and about half of the cytochrome. Their content of ubiquinone is greatly enridhed as compared with chromatophores. Th individual particles have an estimated molecular weight of between 650,000 and 810,000. Gel electrophoresis of the preparation in sodium dodecylsulfate shows polypeptides with molecular weights of 50-45,000, 30,000, 27,000, 22,000 and 12,000. The 50-45,000 components are cytochromes. The 30,000, 27,000 and 22,000 components may be analogous to the triad of polypeptides present in Rhodopseudomonas spheroides reaction centers. The non-cytochrome components are partly soluble in chloroform/methanol. Aggregates of particles appear in these preparations. Electron microscopy of the aggregates demonstrates rectilinear lattices of isodiametric particles, 120 A in diameter. These sheet-like structures are one unit thick and typically contain 9-16 members. They appear to arise by aggregation during isolation but are probably similar to native aggregates apparent within chromatophores after treatment with detergents at low salt concentration.

Bacterial Chromatophores↗
PubMed1975

The extent of the stimulated electrical potential decay under phosphorylating conditions and the H+/ATP ratio in Rhodopseudomonas sphaeroides chromatophores following short flash excitation.

1. In chromatophores from Rps. sphaeroides, the stimulation by ADP and Pi of the electric potential decay indicated by the carotenoid shift is greater than the stimulation of the decay of pH change indicated by the colour change of added cresol red under similar conditions. This difference is attributed to H+ consumption during the synthesis of ATP. The ratio of H+ translocated across the membrane to ATP synthesized was estimated to be approximately 1.7 H+/ATP. 2. The stimulation of the electrical potential decay by ADP and Pi was found to be a constant fraction (10%) of the total decay when the flash intensity was varied. No 'critical' or 'threshold' potential was observed. 3. The stimulated electrical potential decay after a second flash, given within a few seconds of the first, was related to the amplitude of the electrical potential produced by the second flash (10%) but neither to the dark time between the flashes, nor to the total extent of the electrical potential above the dark level. These results are consistent with two hypotheses (a) the chromatophores are a mixed population of vesicles, only a small fraction (10%) of which possess an active ATP synthesizing system (b) the activity of the ATP synthesizing system, though driven by a proton motive force, is controlled by electron transport processess. If alternative (a) is correct then the overall single turnover flash yield of 1 ATP per 1470 bacteriochlorophyll measured in (1) would mean that the yield of the active vesicles is approximately 10 ATP per 1470 bacteriochlorophyll or 30 ATP per vesicle. 4. The stimulation of the electrical potential decay by ADP and Pi is approximately 40% less in antimycin-treated chromatophores. It is shown that this is probably a consequence of antimycin-inhibited H+-release on the inside of the chromatophore vesicles following a flash.

Adenosine Diphosphate↗
PubMed1976

Measurement of transmembrane potentials in Rhodospirillum rubrum chromatophores with an oxacarbocyanine dye.

The fluorescent dye 3,3-dipentyloxacarbocyanine (OCC) can be used as a fluorescence probe to measure transmembrane potentials across Rhodospirillum rubrum chromatophore membranes. A reversible fluorescence increase is observed in the light which is sensitive to inhibitors, permeable ions and uncouplers. Partial interchangeability between the electrical potential and the proton concentration gradient has been demonstrated by measurement of the fluorescence increase with OCC and the fluorescence quenching with 9-aminoacridine. OCC fluorescence changes can be induced also in the dark by injection of permeable salts and by rapid pH changes presumably indicating diffusion potentials. Using salt-induced diffusion potentials for calibrating the light signals and with several assumptions, the light-induced potentials were estimated as 170 mV for the maximal signal and 90-110 mV at the steady state. OCC has been shown to apparently increase the electrical conductivity of the chromatophore membrane, a fact which may be relevant to the mechanism of action of this probe. A red shift in the OCC absorption spectrum occurs when mixed with chromatophores, with a difference spectrum maximum at 495 nm. The absorption changes at 495 nm taking place in the light are similar in kinetics to the fluorescence changes. The absorbance spectrum of OCC in organic solvents is red shifted and the extent of the shift depends on the hydrophobicity of the medium. The difference spectrum compared to water in sec-butyl acetate/n-hexane (3 : 1, v/v) with a dipole moment of 5 was nearly identical to that of chromatophore-associated dye. The uncoupling properties of OCC at high concentrations and some difficulties in calibration limit the usefulness of this probe for quantitative measurements of transmembrane potentials.

Bacterial Chromatophores↗
PubMed1977

Delayed fluorescence from bacteriochlorophyll in Chromatium vinosum chromatophores.

Delayed fluorescence from bacteriochlorophyll in Chromatium vinosum chromatophores was studied at room temperature and under intermittent illuminations. The decay of delayed fluorescence was constituted of two components; a fast component decayed with a half time of about 8 ms, a slow one decayed in parallel with the reduction of photooxidized bacteriochlorophyll (P+) with a half time of 100-200 ms. The biphasic decay of delayed fluorescence indicated that a rapid equilibrium was established between the primary electron acceptor and the secondary acceptor. In the presence of o-phenanthroline, the time course of the decay of delayed fluorescence was identical with that of the reduction of P+ in reaction center-rich subchromatophore particles, although they did not necessarily coincide with each other in "intact" chromatophores. The intensity of the slow component was increased and the decay was accelerated at basic pH values. Reagents that dissipate the proton gradient across the chromatophore membranes such as carbonylcyanide m-chlorophenylhydrazone (CCCP) and nigericin accelerated the decay of the slow component. These effects are probably resulting from changes in internal pH of chromatophore vesicles. Reagents that dissipate the membrane potential such as CCCP and valinomycin decreased the intensity.

Bacterial Chromatophores↗
PubMed1978

Flash-induced photophosphorylation in Rhodospirillum rubrum chromatophores. I. The relationship between cytochrome c-420 content and photophosphorylation.

The content of cytochrome c-420 in Rhodospirillum rubrum chromatophores prepared by grinding with alumina is 5--10% of that in whole cells, and 20--40% in chromatophores by 'French' pressing. Flash-induced phosphorylation of various chromatophores which varied in cytochrome content from 7 to 40% is proportional to the cytochrome content. Extrapolating the cytochrome c-420 content to that observed in whole cells, a ratio ATP/P+X- near 1 is calculated. At low flash intensity the phosphorylation per flash is proportional to flash energy. Photophosphorylation in flashes given after a time of several minutes is only slightly dependent on the number of flashes. If the flashes are spaced from 0.1 to 10 s, relative phosphorylation in the first flash is about 70% and in the second 90+ of that observed in the following flashes. Proton binding is not affected by the cytochrome c-420 content and a ratio of H+/P+x- of 2.3 was found. These results can be explained by a working hypothesis in which charge separation occurring at one reaction centre and the resulting electron transport mediated amongst others by c-420, results in the injection of two protons into an ATPase, this in contrast to a chemiosmotic mechanism, where the protons are released in the chromatophore inner space.

Bacterial Chromatophores↗
PubMed1978

Affinity chromatography of H+-translocating adenosine triphosphatase isolated by chloroform extraction of Rhodospirillum rubrum chromatophores. Modification of binding affinity by divalent cations and activating anions.

1. ATPase isolated from Rhodospirillum rubrum by chloroform extraction and purified by gel filtration or affinity chromatography shows three bands (alpha, beta and gamma) upon electrophoresis in sodium dodecyl sulphate. 2. Ca2+-ATPase activity of the preparation is inhibited by aurovertin and efrapeptin but not by oligomycin. Activity may be inhibited by treatment with 4-chloro-7-nitrobenzofurazan and subsequently restored by dithiothreitol. 3. The enzyme fails to reconstitute photophosphorylation in chromatophores depleted of ATPase by sonic irradiation. 4. Most of the active protein from the crude chloroform extract binds to an affinity chromatography column bearing an immobilised ADP analogue but not to a column bearing immobilised pyrophosphate. 5. In the absence of divalent cations, a component with a very high specific activity for Ca2+-ATPase is eluted from the column by 1.6 mM ATP. This protein migrates asa single band on 5% polyacrylamide gel electrophoresis and only possesses three subunits. At 12 mM ATP an inactive protein is eluted which does not run on acid or alkali polyacrylamide gels and shows a complex subunit structure. 6. ATPase preparations prepared by acetone extraction or by sonic irradiation of chromatophores may also be purified 10-fold by affinity chromatography. 7. The inclusion of 5 mM MgCl2 or CaCl2 during affinity chromatography of chloroform ATPase increases the capacity of the column for the enzyme and demands a higher eluting concentration of ATP. 8. When the enzyme is more than 90% inhibited by efrapeptin or 4-chloro-7-nitrobenzofurazan, the binding characteristics of the enzyme are not affected. 9. 10 mM Na2SO3, which greatly stimulates the Ca2+- and Mg2+-dependent ATPase activity of the enzyme and increases Ki (ADP) for Ca2+-ATPase from 50 to 850 micron, prevents binding to the affinity column. Binding may be restored by the addition of divalent cations. 10. Na2SO3 increases the rate of ATP hydrolysis, ATP-driven H+ translocation and ATP-driven transhydrogenase in chromatophores. 11. It is proposed that anions such as sulphite convert the chromatophore ATPase into a form which is a more efficient energy transducer.

Adenosine Triphosphatases↗