The Release of Bound Adenosine Triphosphatase from Isolated Bacterial Membranes and the Properties of the Solubilized Enzyme

Chemiosmotic coupling in oxidative and photosynthetic phosphorylation. 1966

50 years ago Peter Mitchell proposed the chemiosmotic hypothesis for which he was awarded the Nobel Prize for Chemistry in 1978. His comprehensive review on chemiosmotic coupling known as the first "Grey Book", has been reprinted here with permission, to offer an electronic record and easy access to this important contribution to the biochemical literature. This remarkable account of Peter Mitchell's ideas originally published in 1966 is a landmark and must-read publication for any scientist in the field of bioenergetics. As far as was possible, the wording and format of the original publication have been retained. Some changes were required for consistency with BBA formats though these do not affect scientific meaning. A scanned version of the original publication is also provided as a downloadable file in Supplementary Information and can be found online at doi:10.1016/j.bbabio.2011.09.018. See also Editorial in this issue by Peter R. Rich. Original title: CHEMIOSMOTIC COUPLING IN OXIDATIVE AND PHOTOSYNTHETIC PHOSPHORYLATION, by Peter Mitchell, Glynn Research Laboratories, Bodmin, Cornwall, England.

Proline-specific peptidases ofStreptococcus cremorisAM2

The present study identifies proline-specific peptidases found inStreptococcus cremorisAM2. These activities were present prcdominantly in the cytoplasmic fraction of the cells with minor amounts in cell membrane fraction. No evidence vvas found for such activities in either the extracellular fluid used to grow the cells, in the wash fraction or in the cell wall fraction. The involvement of these enzymes in release of free proline from proline-containing peptides is considered.

Purification and characterization of a dipeptidase from Pseudomonas fluorescens ATCC 948

A dipeptidase from a cell extract of Pseudomonas fluorescens ATCC 948 was purified to homogeneity by ion-exchange chromatography, hydroxyapatite chromatography, gel filtration, and FPLC Phenyl Superose chromatography. The enzyme was located in the cytoplasmic fraction. The dipeptidase appeared to be a monomer with a molecular mass of about 46 kDa, and activity was optimal at pH 8.0 and 50 degrees C. Although activity decreased markedly at temperatures > 50 degrees C, about 50% of maximal activity was retained at 10 degrees C. The activity was inhibited by EDTA, but could be reactivated with Co2+ and partially reactivated with Ca2+. Reducing agents, such as dithiothreitol and 8-hydroxyquinoline, also strongly inhibited the enzyme. The dipeptidase hydrolyzed only dipeptides and showed a particular aptitude for substrates containing a hydrophobic AA at the N-terminus. Dipeptides containing a proline residue were not cleaved. Kinetic studies indicated that the dipeptidase hydrolyzed Leu-Leu with a Michaelis-Menten constant of 0.43 mM and a turnover number of 1812/s.

Purification of ATP synthase from Acetobacterium woodii and identification as a Na(+)-translocating F1F0-type enzyme

The ATPase of Acetobacterium woodii was purified after solubilization of membranes with Triton X-100 by poly(ethylene glycol) precipitation and gel filtration. The enzyme consists of at least six subunits of apparent molecular masses of 57, 52, 35, 19, 15 and 4.8 kDa, as determined by SDS/PAGE. The 52-kDa band is immunologically related to the F1F0-ATPase beta subunit of Escherichia coli. The enzyme is not inhibited by vanadate but is inhibited by nitrate, azide and N,N'-dicyclohexylcarbodiimide; the 4.8-kDa subunit specifically reacts with N,N'-dicyclohexyl[14C]carbodiimide, indicating that the enzyme is of the F1F0 type. The enzyme activity is dependent on MgATP (Km = 0.4), has a pH optimum of pH 7-9 and is stimulated by sulfite. ATP hydrolysis is strictly dependent on sodium ions with a Km for Na+ of 0.4 mM. The purified enzyme was reconstituted into liposomes. Upon addition of ATP, primary and electrogenic 22Na+ transport into the lumen of the proteoliposomes was determined. These experiments demonstrate that the ATPase of Acetobacterium woodii is a Na(+)-translocating F1F0-type ATPase.

Energy conservation in malolactic fermentation by Lactobacillus plantarum and Lactobacillus sake

A comparably poor growth medium containing 0.1% yeast extract as sole non-defined constituent was developed which allowed good reproducible growth of lactic acid bacteria. Of seven different strains of lactic acid bacteria tested, only Lactobacillus plantarum and Lactobacillus sake were found to catalyze stoichiometric conversion of L-malate to L-lactate and CO2 concomitant with growth. The specific growth yield of malate fermentation to lactate at pH 5.0 was 2.0 g and 3.7 g per mol with L. plantarum and L. sake, respectively. Growth in batch cultures depended linearly on the malate concentration provided. Malate was decarboxylated nearly exclusively by the cytoplasmically localized malo-lactic enzyme. No other C4-dicarboxylic acid-decarboxylating enzyme activity could be detected at significant activity in cell-free extracts. In pH-controlled continuous cultures, L. plantarum grew well with glucose as substrate, but not with malate. Addition of lactate to continuous cultures metabolizing glucose or malate decreased cell yields significantly. These results indicate that malo-lactic fermentation by these bacteria can be coupled with energy conservation, and that membrane energetization and ATP synthesis through this metabolic activity are due to malate uptake and/or lactate excretion rather than to an ion-translocating decarboxylase enzyme.

Release of the component of Streptococcus faecalis Na(+)-ATPase from the membranes

The Na(+)-stimulated ATPase activity of Streptococcus faecalis was lost by washing the membranes with ethylenediaminetetraacetic acid (EDTA). ATPase activities of both the EDTA extract and the stripped membranes did not show any stimulation by Na+ ions. However, the Na(+)-stimulated ATPase was readily reconstituted by an incubation of these fractions combined. It was only reconstituted from the fractions prepared under the condition that the Na(+)-ATPase is amplified, and not from those boiled or digested by trypsin. Thus, the component of Na(+)-ATPase of this organism is capable of being released from the membranes.

Some features of the Streptococcus faecalis Na(+)-ATPase resemble those of the vacuolar-type ATPases

In the ethylenediaminetetraacetic acid (EDTA) extract prepared from the membranes of Streptococcus faecalis, we found the 330-kDa protein that was coordinately increased with the induction of Na(+)-ATPase. It was missed in the EDTA extract of Nak1, a mutant defective in the Na(+)-ATPase, but restored in that of its revertant, Nak1R. The 330-kDa protein showed the ATP hydrolytic activity by active staining, and mainly consisted of the polypeptides of 73 kDa, 52 kDa and possibly 38 kDa. In addition, the Na(+)-stimulated ATPase of the membranes was sensitive to both nitrate and N-ethylmaleimide, inhibitors for the vacuolar H(+)-ATPase. Thus, the Na(+)-ATPase of this organism has a structure similar to vacuolar H(+)-ATPase.

Mutants of Streptococcus faecalis sensitive to alkaline pH lack Na(+)-ATPase

Alkali-sensitive mutants which grow at pH 7.5 but not at pH 9.5 in Na(+)-rich media were isolated from Streptococcus faecalis ATCC 9790. One of the mutants, designated Nak1, lacked activities of both Na(+)-stimulated ATPase and KtrII (active K+ uptake by sodium ATPase). These activities were restored in a spontaneous revertant designated Nak1R. Active sodium extrusion from Nak1 was observed at pH 7.0, which allows the cells to generate a proton potential, but not at pH 9.5, which reverses the proton potential, making it positive. Sodium extrusion at pH 7.0 was inhibited by addition of dicyclohexylcarbodiimide and protonophores. Even at pH 9.5, Nak1 did grow well in Na(+)-poor media. In Na(+)-rich media at pH 7.5, growth of Nak1 but not that of 9790 was severely inhibited by a protonophore. These results indicate that mutant Nak1 lacks sodium ATPase but contains a sodium/proton antiporter and that sodium ATPase is essential for the growth of this organism at high pH in Na(+)-rich conditions.

Amplification of the Na+-ATPase of Streptococcus faecalis at alkaline pH

The Na+-ATPase activity of Streptococcus faecalis was influenced by the medium pH. Activities of the protonophore-resistant Na+ extrusion and the KtrII (active K+ uptake by the Na+-ATPase) were maximal in the cells grown at pH 9.5, and were minimal in those grown at pH 6.0. In the cells grown at pH 7.5, they were moderately observed. The Na+-stimulated ATPase activity of the cells grown at pH 9.5 was about 4-fold higher than that of the cells grown at pH 6.0. Thus, amplification of the Na+-ATPase is remarkable at alkaline pH in this organism, possibly by an increase of the cytoplasmic Na+ level as a signal.

Regulation of the cytoplasmic pH by a proton-translocating ATPase in Streptococcus faecalis (faecium). A computer simulation

Earlier work from this laboratory led to the proposal that the cytoplasmic pH of streptococcal cells is regulated solely by changes in the amount and activity of a proton-translocating ATPase, F1F0 complex [Kobayashi, H., Suzuki, T. & Unemoto, T. (1986) J. Biol. Chem. 261, 627-630]. We have now examined the proposal with the aid of computer simulation. We find that an increase in the amount of the H+-ATPase is necessary for pH regulation and is sufficient to maintain a constant steady-state cytoplasmic pH. An increase in H+-ATPase activity is insufficient by itself to maintain a constant cytoplasmic pH, but suppresses the initial fluctuation of the pH. When both variations were allowed, the simulated cytoplasmic pH remained constant despite large perturbations, suggesting that this regulatory system has ample capacity to compensate for pH changes. The present work shows that a computer simulation is a useful way to examine a model for biological regulatory system; application of the simulation to other regulatory systems is discussed.

The F1-ATPase from Streptococcus cremoris: isolation, purification and partial characterization

1. The F1-ATPase from the plasma membrane of Streptococcus cremoris HA was released by low ionic shock wash and purified by gel filtration and ion exchange chromatography. 2. The specific activity of the purified F1-ATPase was 25.8 mumol Pi/mg protein/min. 3. Km for ATP was 0.80 mM, and Ki for ADP as a competetive inhibitor 0.40 mM. 4. The purified F1-ATPase consisted of five subunits, alpha, beta, gamma, delta and epsilon, with molecular masses of 47.0, 45.0, 29.5, 22.0 and 13.0 kDa, respectively. 5. The isoelectric point of the enzyme complex was found to be 4.4.

Properties of the N,N'-dicyclohexylcarbodiimide resistant ATPase of Streptococcus cremoris

1. The specific activity of the membrane-bound ATPase of Streptococcus cremoris HA was 1.30 mumol Pi/mg protein/min. 2. Km for ATP as substrate was 0.8 mM. 3. The pH optimum was 8.0 at +37 degrees C. 4. The ATPase was maximally activated with Mg2+/ATP molar ratio of 1:2. 5. Cations activated the enzyme in order: Mg2+ greater than Co2+ greater than Mn2+ greater than Zn2+ greater than Ca2+ greater than K+ greater than Na+. 6. The enzyme was inhibited by oligomycin (27-77%), sodium azide (13-33%) and ouabain (15-22%). N,N'-dicyclohexylcarbodiimide had no effect on the enzyme activity.

A sensitive staining technique for the detection of phosphohydrolase activities after polyacrylamide gel electrophoresis

A sensitive colorimetric method for the determination of Pi in the range 0.5-10 nmol has been adapted for detection of several phosphohydrolase activities in polyacrylamide gels. This procedure, which leads to the formation of a malachite green-phosphomolybdate complex, may be used with many commonly studied enzymes, such as acid and alkaline phosphatases, nucleotidases, and ATPases. Since detergents do not interfere with color development, this assay is useful for monitoring the activity of detergent-solubilized membrane enzymes as well as normally soluble enzymes.

Characterization and solubilization of the membrane-bound ATPase of Mycoplasma gallisepticum

The membrane-bound ATPase of Mycoplasma gallisepticum selectively hydrolyzed purine nucleoside triphosphates and dATP. ADP, although not a substrate, inhibited ATP hydrolysis. The enzyme exhibited a pH optimum of 7.0 to 7.5 and an obligatory requirement for divalent cations. Dicyclohexylcarbodiimide at a concentration of 1 mM inhibited 95% of the ATPase activity at 37 degrees C, with 50% inhibition occurring at 22 microM dicyclohexylcarbodiimide. Sodium or potassium (or both) failed to stimulate activity by greater than 37%. Azide (2.6 mM), diethylstilbestrol (100 micrograms/ml), p-chloromercuribenzoate (1 mM), and vanadate (50 microM) inhibited 50, 91, 89, and 60%, respectively. The ATPase activity could not be removed from the membrane without detergent solubilization. Although most detergents inactivated the enzyme, the dipolar ionic detergent N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (0.1%) solubilized approximately 70% of the enzyme with only a minor loss in activity. The extraction led to a twofold increase in specific activity and retention of inhibition by dicyclohexylcarbodiimide and ADP. Glycerol greatly increased the stability of the solubilized enzyme. The properties of the membrane-bound ATPase are not consistent with any known ATPase. We postulate that the ATPase functions as an electrogenic proton pump.

Altered expression of the H+ ATPase in Streptococcus faecalis membranes

Evidence is presented that expression of the H+ ATPase in S. faecalis is influenced by the extracellular pH and K+ level during growth. Altered expression was detected by assay of F1 ATPase and electrophoretic analysis of membrane proteins. K+-limited growth caused about a 2-fold increase in the F1 ATPase. The effect of growth at pH 6, 7 and 9 was studied. Compared to cells grown at pH 7, growth at pH 6 increased the F1 ATPase about 2-fold while growth at pH 9 reduced the F1 ATPase by nearly 4-fold. The elevated F1 ATPase activity in the pH 6 cells was associated with an increase in the F1 ATPase alpha and beta subunits in the membrane while the decrease in F1 ATPase in the pH 9 cells was associated with a marked loss of the alpha subunit. It is suggested that intracellular protons may act as effectors which regulate expression of the F1F0 gene cluster at the level of translation.

Mg2+ adenosine triphosphatase from cell envelopes of free-living and bacteroid forms of Rhizobium lupini strain NZP2257

A procedure for the purification of Mg2+ adenosine triphosphatase (EC 3.6.1.3) from free-living and bacteroid forms of Rhizobium lupini NZP2257 is described. The enzyme was released from cell envelopes using Triton X-100 and purified by gel filtration on Ultrogel AcA 22, followed by preparative gel electrophoresis on agarose. The purified ATPase had a molecular weight of about 355,000, as determined from sedimentation coefficients on sucrose gradients. Kinetic analysis of activity of the enzyme from free-living R. lupini showed it to be typical of F1-type Mg2+ ATPases from bacteria. Mg stimulated activity at pH 7.0, although, when present as the free ion, Mg caused non-competitive inhibition (K1 = 1.5 mM). Maximum activity with ATP occurred over a broad pH range from 6.0 to 10.5. ATP, GTP, and UTP, and, to a much lesser degree, CTP and ADP, were hydrolyzed by the enzyme. Hydrolysis of glucose 6-phosphate was not observed. The Km for ATP at pH 7.0 was 0.67 and for GTP 1.4 mM. ATPase activity was inhibited by ADP, and competitive with ATP (KI = 0.18 mM). Azide also caused inhibition but fluoride and DCCD had no effect. Native and sodium dodecyl sulfate-gel electrophoretic analysis revealed no obvious differences between ATPases from free-living and bacteroid forms of R. lupini.

In vivo and in vitro incorporation of endogenous nucleotides by the energy-transducing ATPase of Streptococcus faecalis

The soluble ATPase isolated from Streptococcus faecalis membranes containing tightly bound endogenous nucleotides do not exchange in the presence of ATP and Mg+2 added during the purification of the enzyme. In this paper the stoichiometry of endogenous nucleotides in the soluble ATPase obtained from (a) growing cells, (b) nongrowing glycolyzing cells, and (c) isolated cell membranes has been defined. The time course of incorporation was also studied in nongrowing, glycolyzing cells and isolated cell membranes. In all cases, 1-2 mol of nucleotide was bound per mol of enzyme. Maximal incorporation required approximately 1 h at 38 degrees C. Incorporation of cytoplasmic nucleotide into the enzyme occurred by a process of slow exchange for bound nucleotide. N,N'-dicyclohexylcarbodiimide, which inhibits the membrane-bound ATPase and prevents generation of the protonmotive force, had no effect on incorporation of endogenous nucleotides in glycolyzing cells. Treatment of glycolyzing cells with gramicidin D plus K+, which dissipates the protonmotive force but has no effect on ATPase activity, did not inhibit incorporation of nucleotide. These results support the view that the slow exchange-incorporation of endogenous nucleotide(s) is independent of ATP hydrolysis and a protonmotive force. An in vitro system for the study of nucleotide binding at endogenous sites is described.

Purification and characterization of the membrane adenosine triphosphatase complex from the wild-type and N,N'-dicyclohexylcarbodiimide-resistant strains of Streptococcus faecalis

We have purified the F1-F0 adenosine triphosphatase complex from wild-type Streptococcus faecalis ATCC 9790 and an N,N'-dicyclohexylcarbodiimide (DCCD)-resistant mutant strain, SF-dcc-8. For preliminary purification of the complex, reconstituted F1-F0, prepared from isolated F1 adenosine triphosphatase and depleted membranes, was extracted with sodium deoxycholate and fractionated by salt precipitation. By means of two-dimensional gel electrophoresis, the F1-F0 complex was purified as a single, catalytically active band in the first dimension and then resolved into constituent subunits under denaturing conditions in the second dimension. The electrophoretic purification of F1-F0 removed a delta-less form of F1 as well as other impurities, including lipoteichoic acid. Both the DCCD-sensitive and the DCCD-resistant F1-F0 adenosine triphosphatase appeared to consist of eight proteins, five of which corresponded to the F1 subunits alpha, beta,, gamma, delta, and epsilon. The F0 sector proteins, designated M27, M15, and M6, had Mr values of 27,000, 15,000, and 6,000, respectively. There appear to be multiple copies of M6 in the complex. [14C]DCCD reacted specifically and covalently with M6 in the wild-type F1-F0 but failed to label the M6 protein in the complex from the DCCD-resistant strain. It is suggested that DCCD resistance in the SF-dcc-8 mutant may be due to a modification of the M6 protein which hinders access of DCCD to the reactive site.

Membrane H+ conductance of Streptococcus lactis

Membrane conductance to H+ was measured in the anaerobic bacterium Streptoccus lactis by a pulse technique employing a low driving force (0.1 pH unit; 6 mV). Over the pH range of 3.7 to 8.5, a constant value for passive H+ conductance was observed, corresponding to 0.2 mumol of H+/s per p/ unit per g, dry weight (1.6 microS/cm2 of surface area). The pH insensitivity of this low basal H+ conductance supports the idea that a circulation of protons can mediate highly efficiency engery transductions across the membranes of bacteria.

A study of the surface-active properties of the Mg2+-activated ATPase from cytoplasmic membranes of Streptococcus faecalis

The surface activity and enzymic properties of the factor F1, the catalytic moiety of Streptococcus faecalis H+-ATPase, has been studied at the air-water and phospholipid-water interfaces. F1 does not interact with the monolayer phospholipids, hence its adsorption on a biological membrane must be due mainly to its recognition of proteins of the hydrophobic complex. The dimensions of the F1 molecule at the air-water interface have been estimated. In the presence of Mg2+, base area is S = 1.8 . 10(4) A2, height h = 27 A. Bearing in mind the size of a globular subunit, it follows from the measurements that the major F1 subunits should all lie in the same plane. The ATPase activity of F1 at the interface is inversely proportional to the monolayer density. With low density monolayer, the specific ATPase activity is higher at the interface than in the bulk of the solution. Adsorption of F1 at the interface shifts the isoelectric point of tiscussed relative to the proton-active transport mechanism.

Separation of odontoblast Ca2+-ATPase and alkaline phosphatase

Ca2+-ATPase activity was solubilized, partly purified, and separated from nonspecific alkaline phosphatase activity (APase1) of dentinogenically active rat incisor odontoblasts. Attempts were made to extract the enzymes by various agents, such as Triton X-100, deoxycholate, butanol, EDTA, and buffers of decreasing ionic strength. Solubilization by butanol followed by extraction with low concentrations of EDTA proved to be most effective. Purification and separation were done by molecular sieve chromatography. Ca2+-ATPase showed no activity against p-nitrophenyl phosphate (p-NPP) or inorganic pyrophosphate (PPi) and was unaffected by R 8231 [+/-)-6(m-bromophenyl)-5,6-dihydroimidazo(2,1-b)thiazole oxalate]. It was activated by Ca2+ and Mg2+ ions in equimolar concentrations with the substrate. The enzyme was rapidly inactivated in the solubilized state. An apparent molecular weight of about 18,000 was obtained from molecular sieve data. APase, showing activity against ATP, PPi, and p-NPP, was virtually totally inhibited by R 8231. It was activated by Mg2+ ions but slightly reduced in activity by Ca2+ ions. It had an apparent mol. wt. of 79,000. The results provide direct evidence for earlier suggestions of the existence in hard tissue forming cells of two phosphatases active at alkaline pH.

Stimulation by polyamines of carbamylphosphate:glucose phosphotransferase and glucose-6-phosphate phosphohydrolase activities of multifunctional glucose-6-phosphatase

The effects of added polyamines on carbamylphosphate (carbamyl-P):glucose phosphotransferase and glucose-6-phosphate (Glc-6-P) phosphohydrolase activities of rat hepatic D-Glc-6-P phosphohydrolase (EC 3.1.3.9) of intact and detergent-treated microsomes have been investigated. With the former preparation, in the presence of 1.4 mM phosphate substrate and 90 mM D-glucose (phosphotransferase), 1 mM spermine, spermidine, and putrescine activated Glc-6-P phosphohydrolase 67%, 57%, and 35%, respectively. Carbamyl-P:glucose phosphotransferase, under comparable conditions, was activated 57%, 34%, and 18%. NH+4 (0.25--5.0 mM) produced at best but a minor activation (0--14%), while poly(L-lysine) (Mr = 3400; degree of polymerization 16) equimolar relative to other polyamines with respect to ionized free amino groups activated the hydrolase 358% and the transferase 222%. Treatment of microsomes with the detergent deoxycholate reduced, but did not abolish, polyamine-induced activation. The stimulatory effects of polyamines persisted in the presence of excess catalase, indicating their independence from H2O2 formation; and were eliminated in the presence of Ca2+. Kinetic analysis revealed that all tested polyamines decreased the apparent Michaelis constant values for carbamyl-P and Glc-6-P, but had no effect on the Km for glucose. Poly(L-lysine) increased the V value for both Glc-6-P phosphohydrolase and apparent V values for phosphotransferase extrapolated to infinite concentrations of either carbamyl-P or glucose. The other tested polyamines elevated only this last velocity parameter. It is proposed that a major mechanism by which polyamines activate glucose-6-phosphatase-phosphotransferase is through their electrostatic interactions with phospholipids of the membrane of the endoplasmic reticulum of which this enzyme is a part. Conformational alterations thus induced may in turn affect catalytic behavior. It is suggested that polyamines, or similar positively charged peptides, might participate in the cellular regulation of synthetic and hydrolytic activities of glucose-6-phosphatase.

Purification and properties of acetate kinase from Acholeplasma laidlawii

Acetate kinase (EC 2.7.2.1) was purified from Acholeplasma laidlawii cytoplasm by a combination of ammonium sulfate fractionation, gel filtration, diethylaminoethyl-cellulose chromatography, and affinity chromatography on 8-(6-aminohexylamino)-adenosine 5'-triphosphate conjugated to Sepharose 4B. The enzyme was composed of polypeptide chains of about 50,000 molecular weight as estimated from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Under nondenaturating conditions, apparent molecular weights between 64,000 and 130,000 were obtained, depending upon mainly the ionic strength of the test solution. The enzyme had a narrow specificity for phosphate acceptor acids, whereas both purine and pyrimidine nucleoside triphosphates were suitable phosphate donors. Na(+) and K(+) inhibited both acetyl phosphate and adenosine 5'-triphosphate synthesis, and the latter was also inhibited by high concentrations of adenosine 5'-diphosphate and acetyl phosphate. This substrate inhibition was partially abolished by 0.5 M NaCl. The enzyme catalyzed the independent adenosine 5'-diphosphate<-->adenosine 5'-triphosphate and acetate<-->acetyl phosphate exchanges. The rate of the latter was enhanced by the addition of cosubstrate Mg(2+)-adenosine 5'-triphosphate. The high affinity for substrates, except for acetate, indicated that under physiological conditions the direction of the enzymic reaction favors adenosine 5'-triphosphate synthesis. Thus, a mechanism for adenosine 5'-triphosphate generation in mycoplasmas is suggested.

Hydrolysis and synthesis of ATP by membrane-bound ATPase from a motile Streptococcus

ATPase was detected in the membranes of a motile Streptococcus. Maximal enzymic activity was observed at pH 8 and ATP/Mg2+ ratio of 2. Mn2+ and Ca2+ could replace Mg2+ to some extent. Besides ATP, GTP and ITP were substrates. The enzyme was inhibited by N,N'-dicyclohexylcarbodiimide but not by sodium azide, uncouplers or bathophenanthroline. An electrochemical gradient of protons, which was artificially imposed across the membranes of Streptococcus cells by manipulation of either the K+ diffusion potential or the transmembrane pH gradient, led to ATP synthesis. ATP synthesis was abolished by proton conductors, an inhibitor of the ATPase or an increase in the extracellular K+ concentration. A comparison between the phosphate potential and the electrochemical proton gradient showed that the data found are in agreement with a stoichiometry of 2 protons translocated per molecule ATP synthesized.

Membrane ATPase of Bacillus subtilis. I. Purification and properties

The membrane ATPase (EC 3.6.1.3) of Bacillus subtilis can be solubilized by a shock-wash process. Two procedures for purifying the solubilized enzyme are reported. A protease inhibitor, phenylmethane sulfonylfluoride, was introduced in the solubilization and purification step. The resultant ATPase purified by density gradient centrifugation has a molecular weight of 315 000, an s20,w of 13,4 and an amino acid composition very similar to bacterial ATPases already studied. After exposure to polyacrylamide gel electrophoresis in presence of sodium dodecyl sulphate (SDS), or 8 M urea or SDS-urea, the purified ATPase can be dissociated in two non-identical subunits of molecular weights 59 000 (alpha) and 57 000 (beta) with different charges. Kinetic studies showed that Ca2+ or Zn2+ are required for ATPase activity, although Mg2+ was uneffective. At optimal Ca2+ concentration, the Mg2+ has an inhibitory effect. The Km for ATP is 1.3 mM. Inhibitors of the oxydative phosphorylation, of the mitochondrial ATPase and of the (Na+ + K+)-ATPase are studied.

Inhibition, by a protease inhibitor, of the solubilization of the F1-portion of the Mg2+-stimulated adenosine triphosphatase of Escherichia coli

The effects of two protease inhibitors on the solubilization of the membrane-bound Mg2+-adenosine triphosphatase (Mg-ATPase) of Escherichia coli were investigated. p-Aminobenzamidine prevented the solubilization of the Mg-ATPase during treatment of membranes with low-ionic-strength buffers containing ethylenediaminetetraacetic acid. p-Aminobenzamidine did not prevent subsequent solubilization of the Mg-ATPase by treatment of the membranes with chloroform. This method of solubilization yielded a preparation of similar apparent molecular weight but with a 10-fold-increased specific activity as compared with the Mg-ATPase solubilized by washing with low-ionic-strength buffer. However, in contrast to the latter preparation, the chloroform-solubilized Mg-ATPase did not reconstitute ATP-dependent energization of stripped membranes, which were prepared by low-ionic-strength washing in the absence of p-aminobenzamidine. Another protease inhibitor, epsilon-amino-n-caproic acid, did not effect the solubilization of the Mg-ATPase, but did inhibit the loss of activity occurring during concentration, by ultrafiltration, of the Mg-ATPase solublized by the low-ionic-strength treatment.

Specificity of siderophore receptors in membrane vesicles of Bacillus megaterium

Membrane vesicles of Bacillus megaterium strains SK11 and Ard1 bound the ferrischizokinen and ferriferrioxamine B siderhores (iron transport cofactors). An approximately equimolar uptake of both labels of [3H, 59Fe]ferrischizokinen indicated binding of the intact chelate. Binding reached equilibrium in 2 to 5 min, was temperature independent, and was unaltered by the addition of several energy sources. A 91% dissociation of bound [Fe]ferrischizokinen was achieved in 60 s by the addition of excess ferrischizokinen. Ferriaerobactin, a siderophore which is structurally related to ferrischizokinen, caused no detectable release of bound [59Fe]ferrischizokinen. Of several other ferrigydroxamates tested, only ferriferrichrome A achieved the release (11%) of [Fe]ferrischizokinen. Rapid dissociation (92%) of bound [59Fe]ferriferrioxamine B by the addition of ferriferrioxamine B was observed, and a 67% release of [59Fe]ferriferrioxamine B was caused by ferriA2265, its structural relative. Ferrischizokinen, ferriferrichrome A, and ferrirhodotorulic acid produced a 6, 25, and 29% dissociation, respectively, of [59Fe]ferriferrioxamine B; ferriaerobactin caused no dissociation. [59Fe]ferriaerobactin was bound by the membranes, but its dissociation was not effected by unlabeled ferriaerobactin, suggesting no specific receptors for this chelate. The respective binding affinity constants and maximal binding capacities of membrane vesicles of strain SK11 were 2 x 10(7) M-1 and 280 pmol per mg of protein for ferrischizokinen and 7 x 10(7) M-1 and 37 pmol per mg of protein for ferriferrioxamine B. These values in strain Ard1 were, respectively, 1.4 x 10(7) M-1 and 186 pmol per mg of protein for ferrischizokinen and 11 x 10(7) M-1 and 23 pmol per mg of protein for ferriferrioxamine B. Separate, specific binding sites (receptors) for ferrischizokinen and ferriferrioxamine B exist on the vesicles. The ferrischizokinen receptors have a lower affinity but a higher binding capacity (eightfold) than that shown by the ferriferrioxamine B receptor. These receptors may be components of independent transport systems.

In vitro replication of tobacco mosaic virus RNA in tobacco callus cultures: solubilization of membrane-bound replicase and partial purification

A fraction containing membrane-bound tobacco mosaic virus RNA replicase was isolated form tobacco mosaic virus-infected tobacco callus cultures. The replicase activity reached a maximum 60 h after inoculation and then declined. The enzyme activity was insensitive to actinomycin D and DNase. The corresponding fraction from healthy callus contained essentially no activity. The viral RNA synthesis in vitro proceeded linearly for 30 min and required the four nucleotide triphosphates and Mg2+ ions. Mn2+ was a poor substitute for Mg2+. During RNA synthesis the product was at least 70% resistant to RNase in 2X SSC (0.15 M NaCl plus 0.015 M sodium citrate), but completely digested by RNase in 0.1X SSC. Analysis of the product by polns) that appeared to be replicative form and a partially RNase-resistant structure similar to replicative intermediate form. Washing the membrane-bound replicase with Mg2+-deficient buffer solubilized enzyme. The solubulized enzyme was further purified by DEAE-Sephadex column chromatography. The DEAE-purified enzyme was nearly completely dependent upon tobacco mosaic virus RNA for activity. Analysis of the product on a sucrose gradient revealed a double-stranded RNA with sedimentation of 16S and smaller heterogeneous RNase-sensitive products.

Effect of ADP on ATPASE from a strain of Bacillus stearothermophilus

Bacillus stearothermophilus ATCC 12016 was unable to grow at temperatures below 40 degrees C. On incubating the bacteria at the temperatures, ATP in cells disappeared, ADP was accumulated and ATPase (EC 3.6.1.3) was inactivated. When the purified ATPase was incubated at the temperatures for 1 h with 0.17 mM ADP in the presence of MgCl2, the enzyme was completely inactivated. The inactivated enzyme was reactivated on dilution or dialysis or on warming at 65 degrees C. During the incubation of the enzyme sample, the absorbance spectrum of the enzyme changed. On further incubating the sample over 1.5 h, the second step of spectral change occurred together with the change of the circular dichrosim and the dissociation into a lower molecular weight species of the protein. When the enzyme was treated with ADP-MgCl2 at 65 degrees C, the inactivation and conformational change of the enzyme was not observed.