Synthase (H(+) ATPase): coupling between catalysis, mechanical work, and proton translocation

Coupling with electrochemical proton gradient, ATP synthase (F(0)F(1)) synthesizes ATP from ADP and phosphate. Mutational studies on high-resolution structure have been useful in understanding this complicated membrane enzyme. We discuss mainly the mechanism of catalysis in the beta subunit of F(1) sector and roles of the gamma subunit in energy coupling. The gamma-subunit rotation during catalysis is also discussed.

Use of chemical chaperones in the yeast Saccharomyces cerevisiae to enhance heterologous membrane protein expression: high-yield expression and purification of human P-glycoprotein

Utilizing human P-glycoprotein (P-gp), we investigated methods to enhance the heterologous expression of ATP-binding cassette transporters in Saccharomyces cerevisiae. Human multidrug resistance gene MDR1 cDNA was placed in a high-copy 2 mu yeast expression plasmid under the control of the inducible GAL1 promoter or the strong constitutive PMA1 promoter from which P-gp was expressed in functional form. Yeast cells expressing P-gp were valinomycin resistant. Basal ATPase activity of P-gp in yeast membranes was 0. 4-0.7 micromol/mg/min indicating excellent functionality. P-glycoprotein expressed in the protease-deficient strain BJ5457 was found in the plasma membrane and was not N-glycosylated. By use of the PMA1 promoter, P-gp could be expressed at 3% of total membrane protein. The expression level could be further enhanced to 8% when cells were grown in the presence of 10% glycerol as a chemical chaperone. Similarly, glycerol enhanced protein levels of P-gp expressed under control of the GAL1 promoter. Glycerol was demonstrated to enhance posttranslational stability of P-gp. Polyhistidine-tagged P-gp was purified by metal affinity chromatography and reconstituted into proteoliposomes in milligram quantities and its ATPase activity was characterized. Turnover numbers as high as 12 s(-1) were observed. The kinetic parameters K(MgATP)(M), V(max), and drug activation were dependent on the lipid composition of proteoliposomes and pH of the assay and were similar to P-gp purified from mammalian sources. In conclusion, we developed a system for cost-effective, high-yield, heterologous expression of functional P-gp useful in producing large quantities of normal and mutant P-gp forms for structural and mechanistic studies.

Escherichia coli ATP synthase alpha subunit Arg-376: the catalytic site arginine does not participate in the hydrolysis/synthesis reaction but is required for promotion to the steady state

The three catalytic sites of the F(O)F(1) ATP synthase interact through a cooperative mechanism that is required for the promotion of catalysis. Replacement of the conserved alpha subunit Arg-376 in the Escherichia coli F(1) catalytic site with Ala or Lys resulted in turnover rates of ATP hydrolysis that were 2 x 10(3)-fold lower than that of the wild type. Mutant enzymes catalyzed hydrolysis at a single site with kinetics similar to that of the wild type; however, addition of excess ATP did not chase bound ATP, ADP, or Pi from the catalytic site, indicating that binding of ATP to the second and third sites failed to promote release of products from the first site. Direct monitoring of nucleotide binding in the alphaR376A and alphaR376K mutant F(1) by a tryptophan in place of betaTyr-331 (Weber et al. (1993) J. Biol. Chem. 268, 20126-20133) showed that the catalytic sites of the mutant enzymes, like the wild type, have different affinities and therefore, are structurally asymmetric. These results indicate that alphaArg-376, which is close to the beta- or gamma-phosphate group of bound ADP or ATP, respectively, does not make a significant contribution to the catalytic reaction, but coordination of the arginine to nucleotide filling the low-affinity sites is essential for promotion of rotational catalysis to steady-state turnover.

Regulation and reversibility of vacuolar H(+)-ATPase

Arabidopsis thaliana vacuolar H(+)-translocating pyrophosphatase (V-PPase) was expressed functionally in yeast vacuoles with endogenous vacuolar H(+)-ATPase (V-ATPase), and the regulation and reversibility of V-ATPase were studied using these vacuoles. Analysis of electrochemical proton gradient (DeltamuH) formation with ATP and pyrophosphate indicated that the proton transport by V-ATPase or V-PPase is not regulated strictly by the proton chemical gradient (DeltapH). On the other hand, vacuolar membranes may have a regulatory mechanism for maintaining a constant membrane potential (DeltaPsi). Chimeric vacuolar membranes showed ATP synthesis coupled with DeltamuH established by V-PPase. The ATP synthesis was sensitive to bafilomycin A(1) and exhibited two apparent K(m) values for ADP. These results indicate that V-ATPase is a reversible enzyme. The ATP synthesis was not observed in the presence of nigericin, which dissipates DeltapH but not DeltaPsi, suggesting that DeltapH is essential for ATP synthesis.

Mechanical rotation of the c subunit oligomer in ATP synthase (F0F1): direct observation

F0F1, found in mitochondria or bacterial membranes, synthesizes adenosine 5'-triphosphate (ATP) coupling with an electrochemical proton gradient and also reversibly hydrolyzes ATP to form the gradient. An actin filament connected to a c subunit oligomer of F0 was able to rotate by using the energy of ATP hydrolysis. The rotary torque produced by the c subunit oligomer reached about 40 piconewton-nanometers, which is similar to that generated by the gamma subunit in the F1 motor. These results suggest that the gamma and c subunits rotate together during ATP hydrolysis and synthesis. Thus, coupled rotation may be essential for energy coupling between proton transport through F0 and ATP hydrolysis or synthesis in F1.

The gamma-subunit rotation and torque generation in F1-ATPase from wild-type or uncoupled mutant Escherichia coli

The rotation of the gamma-subunit has been included in the binding-change mechanism of ATP synthesis/hydrolysis by the proton ATP synthase (FOF1). The Escherichia coli ATP synthase was engineered for rotation studies such that its ATP hydrolysis and synthesis activity is similar to that of wild type. A fluorescently labeled actin filament connected to the gamma-subunit of the F1 sector rotated on addition of ATP. This progress enabled us to analyze the gammaM23K (the gamma-subunit Met-23 replaced by Lys) mutant, which is defective in energy coupling between catalysis and proton translocation. We found that the F1 sector produced essentially the same frictional torque, regardless of the mutation. These results suggest that the gammaM23K mutant is defective in the transformation of the mechanical work into proton translocation or vice versa.

Stability of the Escherichia coli ATP synthase F0F1 complex is dependent on interactions between gamma Gln-269 and the beta subunit loop beta Asp-301-beta Asp-305

The role of the conserved sequence motif 301DDLTDP306 in the F0F1 ATP synthase beta subunit was assessed by mutagenic analysis in the Escherichia coli enzyme. Mutations gave variable effects on F1 sector activity, stability, and membrane binding to the F0 sector. Upon solubilization, F1 sectors of the betaD302E and betaD305E mutants (betaAsp-302 and betaAsp-305 replaced by glutamate) dissociated into subunits, while mutants with other beta305 substitutions failed to assemble. Membrane ATPase activities of beta301 and 302 mutants were 20-70% of wild type. Replacements of the gamma subunit Gln-269 had similar effects. The membrane ATPase activities of the gammaQ269E or gammaQ269D mutants were significantly lower and their F1 sectors dissociated into subunits upon solubilization. These results suggest that the beta301-305 loop and the gamma subunit region around Gln-269 form a key region for the assembly of alpha3 beta3 gamma complex. These results are consistent with the X-ray crystallographic structure of bovine F1 (J. P. Abrahams, A. G. W. Leslie, R. Lutter, and J. E. Walker (1994) Nature 370, 621-628) where the beta301DDLTD305 loop directly interacts with gammaGln-269.

Mutational analysis of F1F0 ATPase: catalysis and energy coupling

Escherichia coli ATP synthase has eight subunits and functions through transmission of conformational changes between subunits. Extensive mutational analyses identified essential residues for catalysis and conformation transmission. Pseudorevertant studies revealed that beta/alpha and beta/gamma subunits interactions are important for the energy coupling between catalysis and H+ translocation. In this article, we discuss mechanism of catalysis and energy coupling based on our recent mutation studies.

Essential Cys-Pro-Cys motif of Caenorhabditis elegans copper transport ATPase

Caenorhabditis elegans putative copper ATPase (CUA-1) had been functionally expressed in a yeast delta ccc2 mutant (copper ATPase gene disruptant). We found that CUA-1 with Cys-Pro-Cys to Cys-Pro-Ala mutation could not rescue the yeast delta ccc2 mutant, suggesting that the carboxyl terminal cysteine residue in the conserved Cys-Pro-Cys motif is essential for copper transport.

Caenorhabditis elegans cDNA for a Menkes/Wilson disease gene homologue and its function in a yeast CCC2 gene deletion mutant

The full-length cDNA coding for a putative copper transporting P-type ATPase (Cu2+-ATPase) was cloned from Caenorhabditis elegans. The putative Cu2+-ATPase is a 1,238-amino acid protein, and highly homologous to the Menkes and Wilson disease gene products mutations of which are responsible for human defects of copper metabolism. The Saccharomyces cerevisiae mutant with a disrupted CCC2 gene (yeast Menkes/Wilson disease gene homologue) was rescued by the cDNA for the C. elegans Cu2+-ATPase but not by the cDNA with an Asp-786 (an invariant phosphorylation site) to Asn mutation, suggesting that the C. elegans Cu2+-ATPase functions as a copper transporter in yeast. The expressed C. elegans protein was detected in yeast vacuolar membranes by immunofluorescence microscopy. The yeast expression system may facilitate further studies on copper transporting P-type ATPases.

Conformational transmission in ATP synthase during catalysis: search for large structural changes

Escherichia coli ATP synthase has eight subunits and functions through transmission of conformational changes between subunits. Defective mutation at beta Gly-149 was suppressed by the second mutations at the outer surface of the beta subunit, indicating that the defect by the first mutation was suppressed by the second mutation through long range conformation transmission. Extensive mutant/pseudorevertant studies revealed that beta/alpha and beta/gamma subunits interactions are important for the energy coupling between catalysis and H+ translocation. In addition, long range interaction between amino and carboxyl terminal regions of the gamma subunit has a critical role(s) for energy coupling. These results suggest that the dynamic conformation change and its transmission are essential for ATP synthase.

Molecular imaging of Escherichia coli F0F1-ATPase in reconstituted membranes using atomic force microscopy

The structure of Escherichia coli F0F1-ATPase (ATP synthase), and its F0 sector reconstituted in lipid membranes was analyzed using atomic force microscopy (AFM) by tapping-mode operation. The majority of F0F1-ATPases were visualized as spheres with a calculated diameter of approximately 90 angstroms, and a height of approximately 100 angstroms from the membrane surface. F0 sectors were visualized as two different ring-like structures (one with a central mass and the other with a central hollow of greater than or equal to 18 angstroms depth) with a calculated outer diameter of approximately 130 angstroms. The two different images possibly represent the opposite orientations of the complex in the membranes. The ring-like projections of both images suggest inherently asymmetric assemblies of the subunits in the F0 sector. Considering the stoichiometry of F0 subunits, the area of the image observed is large enough to accommodate all three F0 subunits in an asymmetric manner.

Beta subunit Glu-185 of Escherichia coli H(+)-ATPase (ATP synthase) is an essential residue for cooperative catalysis

Glu-beta 185 of the Escherichia coli H(+)-ATPase (ATP synthase) beta subunit was replaced by 19 different amino acid residues. The rates of multisite (steady state) catalysis of all the mutant membrane ATPases except Asp- beta 185 were less than 0.2% of the wild type one; the Asp- beta 185 enzyme exhibited 15% (purified) and 16% (membrane-bound) ATPase activity. The purified inactive Cys- beta 185 F1-ATPase recovered substantial activity after treatment with iodoacetate in the presence of MgCl2; maximal activity was obtained upon the introduction of about 3 mol of carboxymethyl residues/mol of F1. The divalent cation dependences of the S-carboxymethyl- beta 185 and Asp- beta 185 ATPase activities were altered from that of the wild type. The Asp- beta 185, Cys- beta 185, S-carboxymethyl-beta 185, and Gln- beta 185 enzymes showed about 130, 60, 20, and 50% of the wild type unisite catalysis rates, respectively. The S-carboxymethyl- beta 185 and Asp- beta 185 enzymes showed altered divalent cation sensitivities, and the S-carboxymethyl- beta 185 enzyme showed no Mg2+ inhibition. Unlike the wild type, the two mutant enzymes showed low sensitivities to azide, which stabilizes the enzyme Mg-ADP complex. These results suggest that Glu- beta 185 may form a Mg2+ binding site, and its carboxyl moiety is essential for catalytic cooperativity. Consistent with this model, the bovine glutamate residue corresponding to Glu- beta 185 is located close to the catalytic site in the higher order structure (Abrahams, J.P., Leslie, A.G.W., Lutter, R ., and Walker, J.E. (1994) Nature 370, 621-628)

Beta-gamma subunit interaction is required for catalysis by H(+)-ATPase (ATP synthase). Beta subunit amino acid replacements suppress a gamma subunit mutation having a long unrelated carboxyl terminus

The mechanisms of energy coupling and catalytic co-operativity are not yet understood for H(+)-ATPase (ATP synthase). An Escherichia coli gamma subunit frameshift mutant (downstream of Thr-gamma 277) could not grow by oxidative phosphorylation because both mechanisms were defective (Iwamoto, A., Miki, J., Maeda, M., and Futai, M. (1990) J. Biol. Chem. 265, 5043-5048). The defect(s) of the gamma frameshift was obvious, because the mutant subunit had a carboxyl terminus comprising 16 residues different from those in the wild type. However, in this study, we surprisingly found that an Arg-beta 52-->Cys or Gly-beta 150-->Asp replacement could suppress the deleterious effects of the gamma frameshift. The membranes of the two mutants (gamma frameshift/Cys-beta 52 with or without a third mutation, Val-beta 77-->Ala) exhibited increased oxidative phosphorylation, together with 70-100% of the wild type ATPase activity. Similarly, the gamma frameshift/Asp-beta 150 mutant could grow by oxidative phosphorylation, although this mutant had low membrane ATPase activity. These results suggest that the beta subunit mutation suppressed the defects of catalytic cooperativity and/or energy coupling in the gamma mutant, consistent with the notion that conformational transmission between the two subunits is pertinent for this enzyme.

Conserved Glu-181 and Arg-182 residues of Escherichia coli H(+)-ATPase (ATP synthase) beta subunit are essential for catalysis: properties of 33 mutants between beta Glu-161 and beta Lys-201 residues

Twenty-two mutants between beta Glu-161 and beta Lys-201 of Escherichia coli H(+)-ATPase beta subunit could grow by oxidative phosphorylation, but 11 other such mutants, beta Glu-181-->Gln, Asp, Asn, Thr, Ser, Ala, or Lys and beta Arg-182-->Lys, Ala, Glu, or Gln, could not. The beta Asp-181, beta Lys-182, and other defective mutants had 1.4, 1, and < 0.1%, respectively, of the wild-type membrane ATPase activity. Partially purified F1-ATPases from all mutants at positions 181 and 182, except for the beta Asp-181 and beta Lys-182 mutants, showed very low unisite catalysis. Purified F1-ATPases of the beta Gln-181 and beta Ala-181 mutants showed no multisite (or steady state) catalysis and slow unisite catalysis (< or = 1% of that of the wild type): their defects could be attributed to decreased catalytic rates (low k+2 and k-2). Changes of the k+2 and k-2 values in the beta Asp-181 enzyme, which showed detectable multi- and unisite catalysis, were less marked (27 and 21%, respectively, of wild-type rates). The beta Gln-182 enzyme showed defective catalysis (< or = 0.1% of the multi- and approximately 1% of the unisite catalyses of the wild type), whereas the beta Lys-182 enzyme showed 1 and 85% of the wild-type multisite and unisite catalytic rates, respectively. beta Lys-182 had wild-type values of k+2 and k-2, but beta Gln-182 had k+2 about 10-fold lower than that of wild type.(ABSTRACT TRUNCATED AT 250 WORDS)

Catalysis and energy coupling of H(+)-ATPase (ATP synthase): molecular biological approaches

The molecular biological approach has provided important information for understanding the F0F1 H(+)-ATPase. This article focuses on our recent results on the catalytic site in the beta subunit, and the roles of alpha/beta subunit interaction and amino/carboxyl terminal interaction of the gamma subunit in energy coupling. Extensive mutagenesis of the beta subunit revealed that beta Lys-155, beta Thr-156, beta Glu-181 and beta Arg-182 are essential catalytic residues. beta Glu-185 is not absolutely essential, but a carboxyl residue may be necessary at this position. A pseudo-revertant analysis positioned beta Gly-172, beta Ser-174, beta Glu-192 and beta Val-198 in the proximity of beta Gly-149. The finding of the roles of beta Gly-149, beta Lys-155, and beta Thr-156 emphasized the importance of the glycine-rich sequence (Gly-X-X-X-X-Gly-Lys-Thr/Ser, E. coli beta residues between beta Gly-149 and beta Thr-156) conserved in many nucleotide binding proteins. The A subunits of vacuolar type ATPases may have a similar catalytic mechanism because they have conserved glycine-rich and Gly-Glu-Arg (corresponding to beta Gly-180-beta Arg-182) sequences. The results of these mutational studies are consistent with the labeling of beta Lys-155 and beta Lys-201 with AP3-PL, and of beta Glu-192 with DCCD [15]. The DCCD-binding residue of a thermophilic Bacillus corresponds to beta Glu-181, an essential catalytic residue discussed above. The defective coupling of the beta Ser-174-->Phe mutant was suppressed by the second mutation alpha Arg-296-->Cys, indicating the importance of alpha/beta interaction in energy coupling. The gamma subunit, especially its amino/carboxyl interaction, seems to be essential for energy coupling between catalysis and transport judging from studies on gamma Met-23-->Lys or Arg mutation and second-site mutations which suppressed the gamma Lys-23 mutation. Thus the conserved gamma Met-23 is not absolutely essential but is located in the important region for amino/carboxyl interaction for energy coupling.

The alpha/beta subunit interaction in H(+)-ATPase (ATP synthase). An Escherichia coli alpha subunit mutation (Arg-alpha 296-->Cys) restores coupling efficiency to the deleterious beta subunit mutant (Ser-beta 174-->Phe)

The Ser-beta 174 residue of the Escherichia coli H(+)-ATPase beta subunit has been shown to be near the catalytic site together with Gly-beta 149, Gly-beta 172, Glu-beta 192, and Val-beta 198 (Iwamoto, A., Park, M.-Y., Maeda, M., and Futai, M. (1993) J. Biol. Chem. 268, 3156-3160). In this study, we introduced various residues at position 174 and found that the larger the side chain volume of the residue introduced, the lower the enzyme activity became. The Phe-beta 174 mutant was defective in energy coupling between catalysis and transport, whereas the Leu-beta 174 mutant could couple efficiently, although both mutants had essentially the same ATPase activities (approximately 10% of the wild type). The defective energy coupling of the Phe-beta 174 mutant was suppressed by the second mutation (Arg-alpha 296-->Cys) in the alpha subunit. The Cys-alpha 296/Phe-beta 174 mutant had essentially the same membrane ATPase activity as the Phe-beta 174 single mutant when assayed under the conditions that stabilize the double mutant enzyme. These results indicate the importance of the alpha/beta interaction, especially that between the regions near Arg-alpha 296 and Ser-beta 174, for energy coupling in the H(+)-ATPase. The 2 residues (Ser-beta 174 and Arg-alpha 296) may be located nearby at the interface of the two subunits. About 1 mol of N-[14C]ethylmaleimide could bind to 1 mol of the alpha subunit of Cys-alpha 296/Phe-beta 174 or Cys-alpha 296 mutant ATPase, but could not inhibit the enzyme activity. This is the first intersubunit mutation/suppression approach to ATPase catalysis and its energy coupling.

Escherichia coli F0F1-ATPase. Residues involved in catalysis and coupling

The molecular biological approach has provided important information toward understanding the complexities of the F0F1 ATPase. This article focuses on our recent results on the ATPase catalytic site contained in the beta subunit and the role of the gamma subunit in regulation of proton transport. We used a combination of affinity labeling and mutagenesis to locate several residues of the alpha and beta subunits in the catalytic site. Adenosine triphosphopyridoxal (AP3-PL) labeled beta Lys-155, beta Lys-201 and alpha Lys-201, suggesting that they are near the gamma-phosphate moiety of ATP. Turning to a mutagenesis approach we demonstrated that the two conserved residues, beta Lys-155 and beta Thr-156 in the glycine-rich sequence, are essential for catalysis. Finally, using pseudorevertant analysis, we positioned residue beta Gly-149 (also in the glycine-rich sequence) in proximity to beta Ser-174, beta Glu-192 (binding site for DCCD), and beta Val-198 (only three residues away from the AP3-PL binding site, beta Lys-201). Genetic studies suggested that the gamma subunit plays a role in regulation of catalysis and its coupling with proton conduction. We found that four mutations in the carboxyl-terminal region (gamma Gln-269-->Leu, gamma Gly-275-->Lys, gamma Thr-277-->end, or frameshift) had similar membrane ATPase activities but different ATP-dependent proton pumping and growth by oxidative phosphorylation. These results suggested a perturbation in the coupling between catalysis and proton translocation. We were able to clearly define the "uncoupling" by introducing mutations in the amino-terminal region of the gamma subunit. We were led to gamma Met-23-->Lys and Arg which resulted in an enzyme still regulated by delta microH+, but with profoundly inefficient coupling between ATPase catalytic sites and proton translocation in both ATP-dependent proton pumping and delta microH(+)-driven ATP synthesis. Second-site mutations in the carboxyl-terminal region of the gamma subunit reversed this effect.

Escherichia coli ATP synthase (F-ATPase): catalytic site and regulation of H+ translocation

We discuss our recent results on the Escherichia coli F-ATPase, in particular its catalytic site in the beta subunit and regulation of H+ transport by the gamma subunit. Affinity labelling experiments suggest that beta Lys-155 in the glycine-rich sequence is near the gamma-phosphate moiety of ATP bound at the catalytic site. The enzyme loses activity upon introduction of missense mutations in beta Lys-155 or beta Thr-156 and changes catalytic properties upon introduction of other mutations. By analysis of mutations and their pseudo revertants, residues beta Ser-174, beta Glu-192 and beta Val-198 were found to be located near the glycine-rich sequence. The combined approaches of chemical labelling and genetics have been fruitful in visualizing the structure of the catalytic site. Analysis of mutations in the gamma subunit suggests that this subunit has an essential role in coupling catalysis with proton translocation.

Effects of mutations of conserved Lys-155 and Thr-156 residues in the phosphate-binding glycine-rich sequence of the F1-ATPase beta subunit of Escherichia coli

beta Lys-155 in the glycine-rich sequence of the beta subunit of Escherichia coli F1-ATPase has been shown to be near the gamma-phosphate moiety of ATP by affinity labeling (Ida, K., Noumi, T., Maeda, M., Fukui, T., and Futai, M. (1991) J. Biol. Chem. 266, 5424-5429). For examination of the roles of beta Lys-155 and beta Thr-156, mutants (beta Lys-155-->Ala, Ser, or Thr; beta Thr-156-->Ala, Cys, Asp, or Ser; beta Lys-155/beta Thr-156-->beta Thr-155/beta Lys-156; and beta Thr-156/beta Val-157-->beta Ala-156/beta Thr-157) were constructed, and their properties were studied extensively. The beta Ser-156 mutant was active in ATP synthesis and had approximately 1.5-fold higher membrane ATPase activity than the wild type. Other mutants were defective in ATP synthesis, had < 0.1% of the membrane ATPase activity of the wild type, and showed no ATP-dependent formation of an electrochemical proton gradient. The mutants had essentially the same amounts of F1 in their membranes as the wild type. Purified mutant enzymes (beta Ala-155, beta Ser-155, beta Ala-156, and beta Cys-156) showed low rates of multisite (< 0.02% of the wild type) and unisite (< 1.5% of the wild type) catalyses. The k1 values of the mutant enzymes for unisite catalysis were lower than that of the wild type: not detectable with the beta Ala-156 and beta Cys-156 enzymes and 10(2)-fold lower with the beta Ala-155 and beta Ser-155 enzymes. The beta Thr-156-->Ala or Cys enzyme showed an altered response to Mg2+, suggesting that beta Thr-156 may be closely related to Mg2+ binding. These results suggest that beta Lys-155 and beta Thr-156 are essential for catalysis and are possibly located in the catalytic site, although beta Thr-156 could be replaced by a serine residue.

A glycine-rich sequence in the catalytic site of F-type ATPase

Affinity labeling and genetic studies on the glycine-rich sequence of the beta subunit of E. coli F-type ATPase are discussed. A model of the structure of the enzyme near the gamma phosphate moiety is proposed.

Mutations in Ser174 and the glycine-rich sequence (Gly149, Gly150, and Thr156) in the beta subunit of Escherichia coli H(+)-ATPase

A sequence motif in the beta subunit of Escherichia coli F1 (Gly-Gly-Ala-Gly-Val-Gly-Lys-Thr, residue 149-156, where conserved residues are underlined) is one of the glycine-rich sequences found in many nucleotide binding proteins. In this study, we constructed a plasmid carrying all the F0F1 genes. This plasmid gave the highest membrane ATPase activity so far reported. Substitution of beta Gly149 by Ser suppressed the effect of the beta Ser174----Phe mutation (defective H(+)-ATPase), but beta Gly150----Ser substitution did not have this effect. A single mutation (beta Gly149----Ser or beta Gly150----Ser) gave active enzyme with altered divalent cation dependency and azide sensitivity: the beta Gly149----Ser mutant enzyme had 100-fold lower azide sensitivity and essentially no Ca(2+)-dependent activity, but had the wild-type level of Mg(2+)-dependent activity with active oxidative phosphorylation. Introduction of a beta Gly149----Ser or beta Gly150----Ser mutation with the beta Ser174----Phe mutation also lowered the Ca(2+)-dependent activity and azide sensitivity. Consistent with our previous findings (Takeyama, M., Ihara, K., Moriyama, Y., Noumi, T., Ida, K., Tomioka, N., Itai, A., Maeda, M., and Futai, M. (1990) J. Biol. Chem. 265, 21279-21284), a beta Thr156----Ala or Cys mutation impaired ATPase activity, suggesting that the hydroxyl moiety at position 156 is essential for the catalytic activity. The possible location of the catalytic site including divalent cation binding site(s) is discussed.