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

Generation of a membrane potential by Lactococcus lactis through aerobic electron transport

Lactococcus lactis, a facultative anaerobic lactic acid bacterium, is known to have an increased growth yield when grown aerobically in the presence of heme. We have now established the presence of a functional, proton motive force-generating electron transfer chain (ETC) in L. lactis under these conditions. Proton motive force generation in whole cells was measured using a fluorescent probe (3',3'-dipropylthiadicarbocyanine), which is sensitive to changes in membrane potential (Delta psi). Wild-type cells, grown aerobically in the presence of heme, generated a Delta psi even in the presence of the F(1)-F(o) ATPase inhibitor N,N'-dicyclohexylcarbodiimide, while a cytochrome bd-negative mutant strain (CydA Delta) did not. We also observed high oxygen consumption rates by membrane vesicles prepared from heme-grown cells, compared to CydA Delta cells, upon the addition of NADH. This demonstrates that NADH is an electron donor for the L. lactis ETC and demonstrates the presence of a membrane-bound NADH-dehydrogenase. Furthermore, we show that the functional respiratory chain is present throughout the exponential and late phases of growth.

Absence of malolactic activity is a characteristic of H+-ATPase-deficient mutants of the lactic acid bacterium Oenococcus oeni

The lack of malolactic activity in H(+)-ATPase-deficient mutants of Oenococcus oeni selected previously was analyzed at the molecular level. Western blot experiments revealed a spot at 60 kDa corresponding to the malolactic enzyme only in the parental strain. Moreover, the mleA transcript encoding the malolactic enzyme was not detected by reverse transcription (RT)-PCR analysis of mutants. These results suggest that the malolactic operon was not transcribed in ATPase-deficient mutants. The mleR gene encoding a LysR-type regulatory protein which should be involved in expression of the malolactic genes was described previously for O. oeni. Results obtained in this study show that the mleR transcript was not detected in the mutants by RT-PCR. No mutation in the nucleotide sequences of the mleR gene and the malolactic operon was found. The effect of a reduction in H(+)-ATPase activity on L-malate metabolism was then investigated by using other malolactic bacteria. Spontaneous H(+)-ATPase-deficient mutant strains of Lactococcus lactis and Leuconostoc mesenteroides were isolated by using neomycin resistance. Two mutants were selected. These mutants exhibited ATPase activities that were reduced to 54 and 70% of the activities obtained for the L. lactis and L. mesenteroides parental strains, respectively. These mutants were also acid sensitive. However, in contrast to the ATPase-deficient mutants of O. oeni, activation of L-malate metabolism was observed with the L. lactis and L. mesenteroides mutants under optimal or acidic growth conditions. These data support the suggestion that expression of the genes encoding malolactic enzymes in O. oeni is regulated by the mleR product, as it is in L. lactis. Nevertheless, our results strongly suggest that there is a difference between the regulation of expression of the malolactic locus in O. oeni and the regulation of expression of this locus in less acidophilic lactic acid bacteria.

Inorganic cation transport and energy transduction in Enterococcus hirae and other streptococci

Energy metabolism by bacteria is well understood from the chemiosmotic viewpoint. We know that bacteria extrude protons across the plasma membrane, establishing an electrochemical potential that provides the driving force for various kinds of physiological work. Among these are the uptake of sugars, amino acids, and other nutrients with the aid of secondary porters and the regulation of the cytoplasmic pH and of the cytoplasmic concentration of potassium and other ions. Bacteria live in diverse habitats and are often exposed to severe conditions. In some circumstances, a proton circulation cannot satisfy their requirements and must be supplemented with a complement of primary transport systems. This review is concerned with cation transport in the fermentative streptococci, particularly Enterococcus hirae. Streptococci lack respiratory chains, relying on glycolysis or arginine fermentation for the production of ATP. One of the major findings with E. hirae and other streptococci is that ATP plays a much more important role in transmembrane transport than it does in nonfermentative organisms, probably due to the inability of this organism to generate a large proton potential. The movements of cations in streptococci illustrate the interplay between a variety of primary and secondary modes of transport.

Relationship between the F0F1-ATPase and the K(+)-transport system within the membrane of anaerobically grown Escherichia coli. N,N'-dicyclohexylcarbodiimide-sensitive ATPase activity in mutants with defects in K(+)-transport

A considerable (2-fold) stimulation of the DCCD-sensitive ATPase activity by K+ or Rb+, but not by Na+, over the range of zero to 100 mM was shown in the isolated membranes of E. coli grown anaerobically in the presence of glucose. This effect was observed only in parent and in the trkG, but not in the trkA, trkE, or trkH mutants. The trkG or the trkH mutant with an unc deletion had a residual ATPase activity not sensitive to DCCD. A stimulation of the DCCD-sensitive ATPase activity by K+ was absent in the membranes from bacteria grown anaerobically in the presence of sodium nitrate. Growth of the trkG, but not of other trk mutants, in the medium with moderate K+ activity did not depend on K+ concentration. Under upshock, K+ accumulation was essentially higher in the trkG mutant than in the other trk mutant. The K(+)-stimulated DCCD-sensitive ATPase activity in the membranes isolated from anaerobically grown E. coli has been shown to depend absolutely on both the F0F1 and the Trk system and can be explained by a direct interaction between these transport systems within the membrane of anaerobically grown bacteria with the formation of a single supercomplex functioning as a H(+)-K+ pump. The trkG gene is most probably not functional in anaerobically grown bacteria.

Complementation of an Enterococcus hirae (Streptococcus faecalis) mutant in the alpha subunit of the H(+)-ATPase by cloned genes from the same and different species

We isolated an Enterococcus hirae (formerly Streptococcus faecalis) mutant, designated MS117, in which 'G' at position 301 of the alpha-subunit gene of the F1F0 type of H(+)-ATPase was deleted. MS117 had low H(+)-ATPase activity, was deficient in the regulatory system of cytoplasmic pH, and was unable to grow at pH 6.0. When the alpha-subunit gene of E. hirae H(+)-ATPase was ligated with the shuttle vector pHY300PLK at the downstream region of the tet gene of the vector, it was expressed without its own promoter in MS117, and the mutation of MS117 was complemented; the mutant harbouring the plasmid had the ability to maintain a neutral cytoplasm and grew at pH 6.0. We next transformed MS117 with pHY300PLK containing the alpha-subunit gene of Bacillus megaterium F1F0-ATPase constructed in the same way. The transformant grew at pH 6.0, and the ATP hydrolysis activity was recovered. These results suggested that an active hybrid H(+)-ATPase containing the B. megaterium alpha subunit was produced, and that the hybrid enzyme regulated the enterococcal cytoplasmic pH, although the function of the B. megaterium enzyme did not include pH regulation. Thus, our present results support the previous proposal that the enterococcal cytoplasmic pH is regulated by the F1F0 type of H(+)-ATPase.

Gene structure of Enterococcus hirae (Streptococcus faecalis) F1F0-ATPase, which functions as a regulator of cytoplasmic pH

Enterococcus hirae (formerly Streptococcus faecalis) ATCC 9790 has an F1F0-ATPase which functions as a regulator of the cytoplasmic pH but does not synthesize ATP. We isolated four clones which contained genes for c, b, delta, and alpha subunits of this enzyme but not for other subunit genes. It was revealed that two specific regions (upstream of the c-subunit gene and downstream of the gamma-subunit gene) were lost at a specific site in the clones we isolated, suggesting that these regions were unstable in Escherichia coli. The deleted regions were amplified by polymerase chain reaction, and the nucleotide sequences of these regions were determined. The results showed that eight genes for a, c, b, delta, alpha, gamma, beta, and epsilon subunits were present in this order. Northern (RNA) blot analysis showed that these eight genes were transcribed to one mRNA. The i gene was not found in the upper region of the a-subunit gene. Instead of the i gene, this operon contained a long untranslated region (240 bp) whose G + C content was only 30%. There was no typical promoter sequence such as was proposed for E. coli, suggesting that the promoter structure of this species is different from that of E. coli. Deduced amino acid sequences suggested that E. hirae H(+)-ATPase is a typical F1F0-type ATPase but that its gene structure is not identical to that of other bacterial F1F0-ATPases.

The F1-type ATPase in anaerobic Lactobacillus casei

An ATPase from anaerobic Lactobacillus casei has been isolated and 100-times purified. The 400 kDa enzyme molecule was found to have a hexagonal structure 10 nm in diameter composed of at least six protein masses. SDS-electrophoresis reveals four or, under certain conditions, five types of subunit, of apparent molecular masses 57 (alpha), 55 (beta), 40 (gamma), 22 (delta) and 14 (epsilon) kDa with stoichiometry of 3 alpha, 3 beta, gamma, delta, epsilon. The following features resembling F1-ATPases from other sources were found to be inherent in the solubilized L. casei ATPase. (i) Detachment from the membrane desensitizes ATPase to low DCCD concentrations and sensitizes it to water-soluble carbodiimide. (ii) Soluble ATPase is inhibited by Nbf chloride and azide, is resistant to SH-modifiers and is activated by sulfite and octyl glucoside, the activating effect being much stronger than in the case of the membrane-bound ATPase. Substrate specificity of the enzyme is also similar to that of other factors F1. Divalent cations strongly activate the soluble enzyme when added at a concentration equal to that of ATP. An excess of Mn2+, Mg2+ or Co2+ inhibits ATPase activity of F1, whereas that of Ca2+ induces its further activation. No other F1-like ATPases are found in L. casei. It is concluded that this anaerobic bacterium possesses a typical F1-ATPase similar to those in mitochondria, chloroplasts, aerobic and photosynthetic eubacteria.

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.

Bacterial adenosine 5'-triphosphate synthase (F1F0): purification and reconstitution of F0 complexes and biochemical and functional characterization of their subunits

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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.

Recent developments on structural and functional aspects of the F1 sector of H+-linked ATPases

This review concerns the catalytic sector of F1 factor of the H+-dependent ATPases in mitochondria (MF1), bacteria (BF1) and chloroplasts (CF1). The three types of F1 have many similarities with respect to the structural parameters, subunit composition and catalytic mechanism. An alpha 3 beta 3 gamma delta epsilon stoichiometry is now accepted for MF1 and BF1; the alpha 2 beta 2 gamma 2 delta 2 epsilon 2 stoichiometry for CF1 remains as matter of debate. The major subunits alpha, beta and gamma are equivalent in MF1, BF1 and CF1; this is not the case for the minor subunits delta and epsilon. The delta subunit of MF1 corresponds to the epsilon subunit of BF1 and CF1, whereas the mitochondrial subunit equivalent to the delta subunit of BF1 and CF1 is probably the oligomycin sensitivity conferring protein (OSCP). The alpha beta gamma assembly is endowed with ATPase activity, beta being considered as the catalytic subunit and gamma as a proton gate. On the other hand, the delta and epsilon subunits of BF1 and CF1 most probably act as links between the F1 and F0 sectors of the ATPase complex. The natural mitochondrial ATPase inhibitor, which is a separate protein loosely attached to MF1, could have its counterpart in the epsilon subunit of BF1 and CF1. The generally accepted view that the catalytic subunit in the different F1 species is beta comes from a number of approaches, including chemical modification, specific photolabeling and, in the case of BF1, use of mutants. The alpha subunit also plays a central role in catalysis, since structural alteration of alpha by chemical modification or mutation results in loss of activity of the whole molecule of F1. The notion that the proton motive force generated by respiration is required for conformational changes of the F1 sector of the H+-ATPase complex has gained acceptance. During the course of ATP synthesis, conversion of bound ADP and Pi into bound ATP probably requires little energy input; only the release of the F1-bound ATP would consume energy. ADP and Pi most likely bind at one catalytic site of F1, while ATP is released at another site. This mechanism, which underlines the alternating cooperativity of subunits in F1, is supported by kinetic data and also by the demonstration of partial site reactivity in inactivation experiments performed with selective chemical modifiers. One obvious advantage of the alternating site mechanism is that the released ATP cannot bind to its original site.(ABSTRACT TRUNCATED AT 400 WORDS)