Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.3.14 (ATP synthase)
7,042 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Site-directed mutagenesis was used to investigate the restrictions on Ala-79 of the b subunit in F1F0 adenosine triphosphate synthase. This amino acid had been previously identified as particularly sensitive to mutation (McCormick, K. A., and Cain, B. D. (1991) J. Bacteriol. 173, 7240-7248). Mutant uncF (b) genes were placed under control of the lac promoter and monitored for F1F0 ATP synthase function in an uncF(b) deletion strain. Three deleterious bAla-79 mutations were moved to the unc operon in the chromosome by homologous recombination. Decreases in enzymatic activity in the uncF (b) mutant strains resulted from reduced amounts of enzyme. With the exception of the bAla-79-->Pro mutation, high expression of mutant uncF (b) genes resulted in increases in F1F0 ATP synthase activity which were sufficient to overcome the defects. In addition to the decrease in the amount of enzyme, the bAla-79-->Lys mutation affected ATP synthesis to a much greater extent than ATP-driven proton translocation. The evidence supports our earlier hypothesis, in which bAla-79 was proposed to play an important, but not essential, structural role in F1F0 ATP synthase assembly or stability.
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PMID:Characterization of mutations in the b subunit of F1F0 ATP synthase in Escherichia coli. 822 28

The sequence (Gly-X-X-X-X-Gly-Lys-Thr/Ser) is conserved in nucleotide binding proteins including the alpha and beta subunits of the ATP synthase. Various mutations were introduced in the alpha Lys-175 and alpha Thr-176 residues in the sequence (Gly-Asp-Arg-Gln-Thr-Gly-Lys-Thr, residues 169-176) of the Escherichia coli ATP synthase alpha subunit. Surprisingly, single amino acid substitutions drastically affected the subunit assembly of the enzyme. The entire enzyme assembly was lost by alpha Lys-175-->Phe (or Trp) or alpha Thr-176-->Phe (or Tyr) mutation. Other mutants had similar (alpha His-175, alpha Ser-175, alpha Gly-175, alpha Ser-176, and alpha His-176 mutants) or lower (alpha Ala-176, alpha Cys-176, alpha Leu-176, and alpha Val-176 mutants) effects on assembly of the active enzyme compared with that of the wild-type. However, all these mutant enzymes except the alpha Ser-176 enzyme showed enhanced cold sensitivities and reduced stabilities at high temperature. Mutant enzymes such as alpha Gly-175 and alpha His-176 showed low multi-site (steady state) catalysis, possibly due to loss of proper subunit-subunit interactions. These results suggest that the alpha Lys-175 and alpha Thr-176 residues are not absolutely essential for catalysis, but that they, or possibly the entire conserved sequence, are located in the key domain for the subunit-subunit interactions essential for enzyme stability and steady state activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The alpha subunit of ATP synthase (F0F1): the Lys-175 and Thr-176 residues in the conserved sequence (Gly-X-X-X-X-Gly-Lys-Thr/Ser) are located in the domain required for stable subunit-subunit interaction. 826 95

The monoclonal antibodies (mAb), beta 12 and beta 31, against the beta subunit of Escherichia coli F1-ATPase (Miki, J., Matsuda, T., Kariya, H., Ohmori, H., Tsuchiya, T., Futai, M., and Kanazawa, H. (1992) Arch. Biochem. Biophys. 294, 373-381) recognize the amino-terminal portion of the maximal 104 residues that are not exposed to the surface of the F1-ATPase. To identify the epitope residues within these 104 residues, we introduced random mutations in the region, and clones without binding activity to the mAb, beta 12 and beta 31, were screened. beta subunits defective in binding with mAb beta 12 or beta 31 had amino acid replacements at residues 26, 40, 52, 71, and 74 or at residues 40, 41, 43, 44, 46, and 52, respectively. These residues could be part of the epitope and are possibly located close together. We tested the effects of the mutations on oxidative phosphorylation-dependent growth by introducing expression plasmids of the beta subunit gene with the point mutations into the beta-less mutant, JP17. The alpha and beta subunits were missing from the JP17 membranes, and both subunits were assembled functionally after expression of the beta subunit was induced by introducing the expression plasmid. The replacement of Leu-40 by Pro caused the amounts of the alpha and beta subunits on the membranes to be reduced less than 20% of the amounts in wild type. The replacement of Glu-41 by Lys caused a loss of the alpha subunit on the membranes, without any decrease in the beta subunit. These results indicated that the mutation of Leu-40 to Pro affects the essential role of the beta subunit in the assembly of the alpha and beta subunits on the membranes and that the mutation of Glu-41 to Lys partly affects it. The amino-terminal region of the beta subunit, in particular its ternary structure, including residues 40 and 41, plays an important role in the molecular assembly of the alpha and beta subunits on the membranes.
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PMID:Amino acid replacements at binding sites of monoclonal antibody in the F1-ATPase beta subunit from Escherichia coli caused altered subunit interactions. 830 86

Each of three conserved positively-charged residues in the C-terminal region of subunit 8 of yeast (Saccharomyces cerevisiae) mitochondrial ATP synthase was replaced with isoleucine. The assembly and functional properties of the resulting variants (substituted at Arg-37, Arg-42 and Lys-47) were examined using in-vitro systems to assay import into isolated mitochondria and to monitor assembly into ATP synthase, as well as an in-vivo rescue system using host yeast cells lacking endogenous subunit 8. Each such variant was found to be impaired in assembly in vitro, after import in the form of a chimaeric protein bearing a leader sequence with mitochondrial targeting function. Import precursors bearing a duplicated-leader sequence, engendering enhanced delivery to mitochondria of the passenger variant subunit-8 proteins, enabled assembly of the (Lys-47-->Ile) variant to be detected in vitro but not that of (Arg-37-->Ile) or (Arg-42-->Ile) variants. The respiratory growth of subunit 8-deficient host cells could be rescued with the (Lys-47-->Ile) variant expressed allotopically in the nucleus. Such rescued cells were found to have an enhanced growth rate (comparable to that produced by non-mutagenized parental subunit 8) when delivered to mitochondria with the duplicated-leader sequence, as compared to the single-leader sequence. This confirms that the impediment in the (Lys-47-->Ile) variant lies in the efficiency of its assembly, rather than a functional defect, as such, arising from the loss of that positive charge. In contrast, host cells were unable to be rescued by the (Arg-37-->Ile) and (Arg-42-->Ile) variants, even when they were endowed with the duplicated leader sequence. It is concluded that the positively-charged C-terminal domain of subunit 8, common to fungal and mammalian homologues of this protein, plays a key role in its assembly into mitochondrial ATP synthase.
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PMID:Each of three positively-charged amino acids in the C-terminal region of yeast mitochondrial ATP synthase subunit 8 is required for assembly. 834 59

The a subunit of F1F0 ATP synthase contains a highly conserved region near its carboxyl terminus which is thought to be important in proton translocation. Cassette site-directed mutagenesis was used to study the roles of four conserved amino acids Gln-252, Phe-256, Leu-259, and Tyr-263. Substitution of basic amino acids at each of these four sites resulted in marked decreases in enzyme function. Cells carrying a subunit mutations Gln-252-->Lys, Phe-256-->Arg, Leu-259-->Arg, and Tyr-263-->Arg all displayed growth characteristics suggesting substantial loss of ATP synthase function. Studies of both ATP-driven proton pumping and proton permeability of stripped membranes indicated that proton translocation through F0 was affected by the mutations. Other mutations, such as the Phe-256-->Asp mutation, also resulted in reduced enzyme activity. However, more conservative amino acid substitutions generated at these same four positions produced minimal losses of F1F0 ATP synthase. The effects of mutations and, hence, the relative importance of the amino acids for enzyme function appeared to decrease with proximity to the carboxyl terminus of the a subunit. The data are most consistent with the hypothesis that the region between Gln-252 and Tyr-263 of the a subunit has an important structural role in F1F0 ATP synthase.
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PMID:Mutagenic analysis of the a subunit of the F1F0 ATP synthase in Escherichia coli: Gln-252 through Tyr-263. 838 11

A mutant of the Escherichia coli F1-ATPase, gamma S8C, has been reacted with a novel bifunctional reagent, N-maleimido-N'-(4-azido-2,3,5,6-tetrafluorobenzamido) cystamine (TFPAM-SS1). Modification of Cys-8 via the maleimide, followed by photolysis to convert the azido group to a reactive nitrene, led to cross-linking of the gamma subunit to a beta subunit. When this cross-linking was conducted with ADP + Mg2+ in catalytic sites, the predominant cross-linked product had a M(r) of 108,000. If cross-linking was done with uncleaved ATP + Mg2+ in catalytic sites, cross-linked products of 102,000 and 84,000 were formed. Cross-linking under both conditions led to inhibition of ATPase activity. TFPAM-SS1 could be cleaved by using reducing agents to break the disulfide bond that links the malemide and tetrafluorophenylazide moieties. Cleavage of this disulfide bond after formation of 102,000 and 84,000 species led to full recovery of ATPase activity. When the 108-kDa cross-linked product was cleaved, full activity was not restored, presumably because of insertion of the tetrafluorophenylazide into a functionally important site on the beta subunit. After cleavage of the disulfide bond, the free thiols could be reacted with [14C]N-ethylmaleimide, thereby radioactively tagging the sites of insertion of the tetrafluorophenylnitrene moiety. In this way, the site of cross-linking from Cys-8 of gamma to the beta subunit in the presence of ADP + Mg2+ was localized to within the sequence Val 145-Lys-155, which contains the glycine-rich loop. This loop region is a part of the catalytic site of the enzyme.
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PMID:The gamma subunit of the Escherichia coli F1-ATPase can be cross-linked near the glycine-rich loop region of a beta subunit when ADP + Mg2+ occupies catalytic sites but not when ATP + Mg2+ is bound. 840 13

The gamma subunit mutations, gamma Met-23-->Lys or Arg, in the Escherichia coli ATP synthase were previously reported to cause dramatically inefficient energy coupling between ATPase catalysis and H+ translocation (Shin, K., Nakamoto, R.K., Maeda, M., and Futai, M. (1992) J. Biol. Chem. 267, 20835-20839). In this paper, we report that second-site mutations in the gamma subunit can suppress the effects of gamma Met-23-->Lys. By screening randomly mutagenized uncG (gamma Met-23-->Lys), eight mutations in the carboxyl-terminal region were identified; strains carrying gamma Arg-242-->Cys, gamma Gln-269-->Arg, gamma Ala-270-->Val, gamma Ile-272-->Thr, gamma Thr-273-->Ser, gamma Glu-278-->Gly, gamma Ile-279-->Thr, or gamma Val-280-->Ala in combination with gamma Met-23-->Lys were able to grow by oxidative phosphorylation. H+ pumping assayed in membranes prepared from double mutation strains demonstrated that efficient ATP-dependent H+ transport was restored. Interestingly, the single mutations, gamma Gln-269-->Arg or gamma Thr-273-->Ser, caused reduced growth by oxidative phosphorylation; however, when these mutations were in combination with gamma Met-23-->Lys, growth was substantially increased. Furthermore, strains carrying gamma Met-23-->Lys, gamma Gln-269-->Arg, or gamma Thr-273-->Ser as single mutations were temperature sensitive, whereas, strains with the double mutations, gamma Met-23-->Lys/gamma Gln-269-->Arg or gamma Met-23-->Lys/gamma Thr-273-->Ser, were thermally stable. Taken together, these results strongly suggest that gamma Met-23, gamma Arg-242, and the region between gamma Gln-269 to gamma Val-280 are close to each other and interact to mediate efficient energy coupling.
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PMID:The gamma subunit of the Escherichia coli ATP synthase. Mutations in the carboxyl-terminal region restore energy coupling to the amino-terminal mutant gamma Met-23-->Lys. 841 64

The beta Gly-149 residue is in a glycine-rich sequence (Gly-Gly-Ala-Gly-Val-Gly-Lys-Thr; residues 149-156) of the Escherichia coli H(+)-ATPase (ATP synthase) beta subunit. Substitution of beta Gly-149 by Ser suppressed the effect of the beta Ser-174-->Phe mutation (Iwamoto, A., Omote, H., Hanada, H., Tomioka, N., Itai, A., Maeda, M., and Futai, M. (1991) J. Biol. Chem. 266, 16350-16355), suggesting that beta Gly-149 is located near beta Ser-174. In this study, we introduced different residues at position 149 and found that a single mutant beta Cys-149 was defective. The effect of beta Cys-149 mutation was suppressed by beta Gly-172-->Glu, beta Ser-174-->Phe, beta Glu-192-->Val, or beta Val-198-->Ala replacement. These results suggest that beta Gly-149, beta Gly-172, beta Ser-174, beta Glu-192, and beta Val-198 residues are located close together in the catalytic site. From these findings we propose a model of the catalytic site of the enzyme near the gamma phosphate moiety of ATP. F1 enzymes with the double mutations beta Cys-149/beta Glu-172, beta Cys-149/beta Phe-174, beta Cys-149/beta Val-192, and beta Cys-149/beta Ala-198 were less sensitive than wild-type F1 to dicyclohexylcarbodiimide and adenosine triphosphopyridoxal (an affinity analogue of ATP forming a Schiff base with the epsilon-amino group of beta Lys-155 or beta Lys-201), and became sensitive to N-ethylmaleimide in an ATP-protected manner. These results of inhibitor studies are consistent with the proposed model.
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PMID:Domains near ATP gamma phosphate in the catalytic site of H+-ATPase. Model proposed from mutagenesis and inhibitor studies. 842 92

The Arg-41 of the c-subunit of the F0F1-ATPase of Escherichia coli has been changed by site-directed mutagenesis to Glu, Leu or Lys. None of the mutants can carry out oxidative phosphorylation. No detectable F1-ATPase activity is found on the membranes and only small amounts in the cytoplasm. Two-dimensional gel electrophoresis shows that in all three mutant strains the assembly of the F0F1-ATPase has been affected. When plasmids carrying the mutant genes, together with other normal unc genes, were inserted into strains each carrying a mutation in one of the unc genes other than uncE their capacity for oxidative phosphorylation was reduced or eliminated, the effect being most pronounced with the uncG and uncC mutants and least pronounced with the plasmid giving the Arg-->Lys substitution. The c-subunit is a multimer in the ATP synthase complex and it appears that a mixture of normal and mutant gene products allows assembly of a functional complex.
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PMID:The role of arginine in the conserved polar loop of the c-subunit of the Escherichia coli H(+)-ATPase. 844 8

The "homology A" ("glycine-rich" or "P-loop") consensus sequence occurs in the catalytic sites of F1F0 ATP synthase enzymes. The conserved lysine of this motif is beta-subunit Lys-155 in Escherichia coli F1. The role of this lysine in binding and catalysis at the high affinity ATP binding site was studied with the mutants beta K155Q and beta K155E by measuring the rates of ATP binding/release, ATP hydrolysis/synthesis, and Pi release as a function of pH varied from 5.5 to 9.5. In wild type, protonated beta Lys-155 appears to contribute significantly to high affinity binding of ATP, probably through hydrogen bonding to the gamma-phosphate. ATP hydrolysis and synthesis were impaired strongly in the mutants, and the reaction equilibrium constant, which was pH-independent in wild type, was highly pH-dependent in beta K155Q and beta K155E. Studies of steady-state ATPase turnover showed that positive catalytic cooperativity was virtually absent and the pH-dependent component of positive catalytic cooperativity was abolished or reversed in the mutants. The data demonstrate that residue beta K155 is a critical catalytic residue in F1 ATPase.
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PMID:Lysine 155 in beta-subunit is a catalytic residue of Escherichia coli F1 ATPase. 846 32


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