Studies of energy-linked reactions. Net synthesis of adenosine triphosphate by isolated adenosine triphosphate synthase preparations: a role for lipoic acid and unsaturated fatty acids.
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ABSTRACT:
SUBMITTER: Griffiths DE
PROVIDER: S-EPMC1164299 | biostudies-other | 1976 Dec
REPOSITORIES: biostudies-other
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Project description:1. Small particles from Escherichia coli catalyse an ATP-dependent reduction of NADP(+) by NADH. 2. The reaction was stimulated by Mg(2+) and only ATP and ITP could serve as energy donors. 3. Studies of the stoicheiometry of the reaction indicate that 1-2mol of ATP are utilized/mol of NADH produced. 4. The reaction is inhibited by uncoupling agents such as 2,4-dinitrophenol (200mum) and tetrachlorotrifluorobenzimidazole (2mum) but oligomycin does not inhibit. 5. The reaction is inhibited by relatively high concentrations (200mum) of piericidin A.
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Project description:ATP leads to endothelial NO synthase (eNOS)/NO-mediated vasodilation, a process hypothesized to depend on the endothelial caveolar eNOS partitioning and subcellular domain-specific multisite phosphorylation state. We demonstrate herein that, in both the absence and presence of ATP, the uterine artery endothelial caveolae contain specific protein machinery related to subcellular partitioning and act as specific focal "hubs" for NO- and ATP-related proteins. ATP-induced eNOS regulation showed a complex set of multisite posttranslational phosphorylation events that were closely associated with the enzyme's partitioning between caveolar and noncaveolar endothelial subcellular domains. The comprehensive model that we present demonstrates that ATP repartitioned eNOS between the caveolar and noncaveolar subcellular domains; specifically, the stimulatory (PSer635)eNOS was substantially higher in the caveolar pool with subcellular domain-independent increased levels on ATP treatment. The stimulatory (PSer1179)eNOS was not altered by ATP treatment. However, the inhibitory (PThr495)eNOS was regulated predominantly in the caveolar domain with decreased levels on ATP action. In contrast, the agonist-specific (PSer114)eNOS was localized in the noncaveolar pool with increased levels on ATP stimulation. Thus, the endothelial caveolar membrane system plays a pivotal role(s) in ATP-associated subcellular partitioning and possesses the relevant protein machinery for ATP-induced NO regulation. Furthermore, these subcellular domain-specific phosphorylation/dephosphorylation events provide evidence relating to eNOS spatio-temporal dynamics.
| S-EPMC3337759 | biostudies-literature
Project description:Adenosine triphosphate phosphoribosyltransferase (ATP-PRT) catalyzes the first step in histidine biosynthesis, a pathway essential to microorganisms and a validated target for antimicrobial drug design. The ATP-PRT enzyme catalyzes the reversible substitution reaction between phosphoribosyl pyrophosphate and ATP. The enzyme exists in two structurally distinct forms, a short- and a long-form enzyme. These forms share a catalytic core dimer but bear completely different allosteric domains and thus distinct quaternary assemblies. Understanding enzymatic transition states can provide essential information on the reaction mechanisms and insight into how differences in domain structure influence the reaction chemistry, as well as providing a template for inhibitor design. In this study, the transition state structures for ATP-PRT enzymes from Campylobacter jejuni and Mycobacterium tuberculosis (long-form enzymes) and from Lactococcus lactis (short-form) were determined and compared. Intrinsic kinetic isotope effects (KIEs) were obtained at reaction sensitive positions for the reverse reaction using phosphonoacetic acid, an alternative substrate to the natural substrate pyrophosphate. The experimental KIEs demonstrated mechanistic similarities between the three enzymes and provided experimental boundaries for quantum chemical calculations to characterize the transition states. Predicted transition state structures support a dissociative reaction mechanism with a DN*AN‡ transition state. Weak interactions from the incoming nucleophile and a fully dissociated ATP adenine are predicted regardless of the difference in overall structure and quaternary assembly. These studies establish that despite significant differences in the quaternary assembly and regulatory machinery between ATP-PRT enzymes from different sources, the reaction chemistry and catalytic mechanism are conserved.
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Project description:BACKGROUND:Human PMS2 (hPMS2) homologues act to nick 5' and 3' to misincorporated nucleotides during mismatch repair in organisms that lack MutH. Mn(++) was previously found to stimulate the endonuclease activity of these homologues. ATP was required for the nicking activity of hPMS2 and yPMS1, but was reported to inhibit bacterial MutL proteins from Thermus thermophilus and Aquifex aeolicus that displayed homology to hPMS2. Mutational analysis has identified the DQHA(X)(2)E(X)(4)E motif present in the C-terminus of PMS2 homologues as important for endonuclease activity. METHODOLOGIES/PRINCIPAL FINDINGS:We examined the effect ATP had on the Mn(++) induced nicking of supercoiled pBR322 by full-length and mutant A. aeolicus MutL (Aae MutL) proteins. Assays were single time point, enzyme titration experiments or reaction time courses. The maximum velocity for MutL nicking was determined to be 1.6+/-0.08x10(-5) s(-1) and 4.2+/-0.3x10(-5) s(-1) in the absence and presence of ATP, respectively. AMPPNP stimulated the nicking activity to a similar extent as ATP. A truncated Aae MutL protein composed of only the C-terminal 123 amino acid residues was found to nick supercoiled DNA. Furthermore, mutations in the conserved C-terminal DQHA(X)(2)E(X)(4)E and CPHGRP motifs were shown to abolish Aae MutL endonuclease activity. CONCLUSIONS:ATP stimulated the Mn(++) induced endonuclease activity of Aae MutL. Experiments utilizing AMPPNP implied that the stimulation did not require ATP hydrolysis. A mutation in the DQHA(X)(2)E(X)(4)E motif of Aae MutL further supported the role of this region in endonclease activity. For the first time, to our knowledge, we demonstrate that changing the histidine residue in the conserved CPHGRP motif abolishes endonucleolytic activity of a hPMS2 homologue. Finally, the C-terminal 123 amino acid residues of Aae MutL were sufficient to display Mn(++) induced nicking activity.
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Project description:1. The synthesis of dibutylchloromethyltin chloride, a new covalent inhibitor of the mitochondrial ATP synthase [oligomycin-sensitive ATPase (adenosine triphosphatase)] complex is described, together with a method for preparing dibutylchloro[(3)H]methyltin chloride. 2. Studies with the yeast mitochondrial oligomycin-sensitive ATPase complex show that dibutylchloromethyltin chloride inhibits both the membrane-bound enzyme and also the purified Triton X-100-dispersed preparation. 3. F(1)-ATPase is not inhibited even at 500nmol of dibutylchloromethyltin chloride/mg of protein, and the general inhibitory properties are similar to those of triethyltin, oligomycin and dicyclohexylcarbodi-imide, known energy-transfer inhibitors of oxidative phosphorylation. 4. Binding studies with yeast submitochondrial particles show that dibutylchloromethyltin chloride antagonizes the binding of triethyl[(113)Sn]tin, indicating that there is an interaction between the two inhibitor-binding sites. 5. Unlike triethyltin, inhibition by dibutylchloromethyltin chloride is due to a covalent interaction which titrates a component of the inner mitochondrial membrane present at a concentration of 8-9nmol/mg of protein. 6. All of the labelled component can be extracted with chloroform/methanol (2:1, v/v), and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of the chloroform/methanol extract indicates that the labelled component has an apparent mol.wt. of 6000-8000. However, t.l.c. reveals the presence of only one labelled component which is lipophilic and non-protein and is distinct from the free inhibitor, mitochondrial phospholipids and the dicyclohexylcarbodi-imide-binding protein (subunit 9). 7. Inhibition of mitochondrial ATPase and oxidative phosphorylation is correlated with specific interaction with a non-protein lipophilic component of the mitochondrial inner membrane which is proposed to be a co-factor or intermediate of oxidative phosphorylation.
| S-EPMC1165045 | biostudies-other
Project description:1. A method for the preparation of small particles from Escherichia coli is described. 2. These particles catalyse the ATP-driven reduction of NAD(+) by succinate. 3. ATP utilized/NADH produced ratios below 2.0 were measured and a stoicheiometry of 1 molecule of ATP utilized per molecule of NADH produced is proposed. 4. The reaction is not inhibited by 2,4-dinitrophenol or by oligomycin but is inhibited by other uncouplers such as pentabromophenol and dicoumarol. 5. The specificity of the energy source, the specificity of the electron acceptor, the effects of pH, Mg(2+), P(i) and temperature have been studied.
| S-EPMC1176493 | biostudies-other
Project description:The genome of Chlamydia trachomatis, one of the most prominent human pathogens, contains two structural genes coding for proteins, herein called Npt1Ct and Npt2Ct (nucleoside phosphate transporters 1 and 2 of C. trachomatis), exhibiting 68 and 61% similarity, respectively, to the ATP/ADP transporter from the intracellular bacterium Rickettsia prowazekii at the deduced amino acid level. Hydropathy analysis and sequence alignments suggested that both proteins have 12 transmembrane domains. The putative transporters were expressed as histidine-tagged proteins in Escherichia coli to study their biochemical properties. His10-Npt1Ct catalyzed ATP and ADP transport in an exchange mode. The apparent Km values were 48 (ATP) and 39 (ADP) microM. ATP and ADP transport was specific since AMP, GTP, CTP, UTP, dATP, dCTP, dGTP, and dTTP did not inhibit uptake. In contrast, His10-Npt2Ct transported all four ribonucleoside triphosphates with apparent Km values of 31 microM (GTP), 302 microM (UTP), 528 microM (CTP), and 1,158 microM (ATP). Ribonucleoside di- and monophosphates and deoxyribonucleotides were not substrates. The protonophore m-chlorocarbonylcyanide phenylhydrazone abolished uptake of all nucleoside triphosphates by Npt2Ct. This observation indicated that His10-Npt2Ct acts as a nucleosidetriphosphate/H+ symporter energized by the proton motive force across the Escherichia coli cytoplasmic membrane. We conclude that Npt1Ct provides chlamydiae with energy whereas Npt2Ct catalyzes the net uptake of ribonucleoside triphosphates required for anabolic reactions.
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Project description:Lipoic acid is an essential cofactor required for the function of key metabolic pathways in most organisms. We report the characterization of a Bacillus subtilis mutant obtained by disruption of the lipA (yutB) gene, which encodes lipoyl synthase (LipA), the enzyme that catalyzes the final step in the de novo biosynthesis of this cofactor. The function of lipA was inferred from the results of genetic and physiological experiments, and this study investigated its role in B. subtilis fatty acid metabolism. Interrupting lipoate-dependent reactions strongly inhibits growth in minimal medium, impairing the generation of branched-chain fatty acids and leading to accumulation of copious amounts of straight-chain saturated fatty acids in B. subtilis membranes. Although depletion of LipA induces the expression of the Delta5 desaturase, controlled by a two-component system that senses changes in membrane properties, the synthesis of unsaturated fatty acids is insufficient to support growth in the absence of precursors for branched-chain fatty acids. However, unsaturated fatty acids generated by deregulated overexpression of the Delta5 desaturase functionally replaces lipoic acid-dependent synthesis of branched-chain fatty acids. Furthermore, we show that the cold-sensitive phenotype of a B. subtilis strain deficient in Delta5 desaturase is suppressed by isoleucine only if LipA is present.
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Project description:The chemical synthesis of a adenosine triphosphate analogue, 1-adenosin-5'-yl 3-(3-methylbut-2-enyl) triphosphoric acid diester (ApppD), is described. ApppD is known to be an active metabolite of the mevalonate pathway in the human body like its structural isomer isopentenyl ester of ATP (ApppI). Very recently, ApppI has been found to possess novel function(s); now it will also be possible to examine the effects of ApppD more precisely because it can be synthesized in reasonable amounts. 1-Adenosin-5'-yl 3-(3-methylbut-2-enyl) diphosphoric acid diester (AppD; a adenosine diphosphate analogue) was also isolated from the synthesis mixture. Both ApppD and AppD were characterized by 1H, 13C, 31P NMR and mass spectrometry methods.
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Project description:The subunit makeup of the family of adenosine triphosphate-sensitive potassium channel (KATP) channels is more complex and labile than thought. The growing association of Kir6.1 and SUR2 variants with specific cardiovascular electrical and contractile derangements and the clear association with Cantu syndrome establish the importance of appropriate activity in normal function of the heart and vasculature. Further studies of such patients will reveal new mutations in KATP subunits and perhaps in proteins that regulate KATP synthesis, trafficking, or location, all of which may ultimately benefit therapeutically from the unique pharmacology of KATP channels.
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