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)

1. The content of the membrane sector of the ATPase complex (Fo) in brown adipose tissue mitochondria was determined by means of specific [14C]-DCCD binding. 2. The specific DCCD binding to the F0 protein was distinguished from the nonspecific binding to the other membrane proteins and phospholipids by: (a) Scatchard plot analysis of the equilibrium binding data, (b) SDS-polyacrylamide gel electrophoresis of the 14C-labelled membrane proteins, (c) partial purification of the chloroform-methanol extractable DCCD-binding protein. It was found that the specific DCCD binding was present in three polypeptides of a relative molecular weight of 9000, 16 000 and 32 000. In brown adipose tissue mitochondria the specific binding was 10-times lower than in heart or liver mitochondria. The binding to the other membrane proteins and to phospholipids was quite similar in all mitochondrial preparations studied. 3. The decreased quantity of the specific binding sites in brown adipose tissue mitochondria demonstrated that the reduction of F0 parallels the reduction of the F1-ATPase and revealed that in these mitochondrial membranes the ratio between the respiratory chain enzymes and the ATPase complex is 10- to 20- times higher than in heart or liver mitochondria.
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PMID:Evaluation of the specific dicyclohexylcarbodiimide binding sites in brown adipose tissue mitochondria. 645 Dec 41

1. Preincubation of the ox heart chloroform-released mitochondrial ATPase with MgATP results in a time-dependent inhibition of ATPase activity. No re-activation occurs when MgATP remains in the preincubation medium. The enzyme activity returns when all the MgATP in the preincubation system has been hydrolysed. 2. The mechanism of the MgATP-induced inhibition was examined. Inhibition occurs on incubation with MgATP or other hydrolysable nucleotides. Incubation with MgADP or Pi does not cause any inhibition. Neither freshly bound adenine nucleotide nor Pi is associated with inhibited enzyme. The rate of MgATP-induced inhibition correlates with the rate of ATP hydrolysis in the preincubation medium. Changing the rate of ATP hydrolysis at a fixed concentration of ATP also changes the rate of MgATP-induced inhibition by the same proportion. The inhibition is thus related to the ATP-hydrolysis process itself. 3. We propose that intermediate enzyme species of the ATP-hydrolytic sequence can undergo a conformational change to form inhibited species. The kinetics of the inhibition suggest that a substrate-activation step is involved in ATP hydrolysis and MgATP-induced inhibition. 4. The effects of the nature of the preincubation medium on the process of MgATP-induced inhibition and its reversal were examined.
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PMID:MgATP-induced inhibition of the adenosine triphosphatase activity of the chloroform-released mitochondrial adenosine triphosphatase. 645 83

The general anesthetics chloroform and halothane inhibit ATP synthesis in rat liver mitochondria, in the millimolar concentration range (1-12 mM), in parallel with a reduction of respiratory control and the ratio of ATP produced to oxygen consumed. In these effects, halothane and chloroform are similar to classical, protonophoric, uncouplers. The rate of ADP-stimulated respiration or the rate of uncoupler-stimulated respiration is not affected. Like classical uncouplers, halothane and chloroform also stimulate mitochondrial ATPase activity. However, the extent of stimulation by these agents is larger than by protonophoric uncouplers and, more significantly, ATPase activity stimulated by carbonylcyanide m-chlorophenylhydrazone is further stimulated by these agents. In the presence of the Ca2+ chelator EGTA, halothane and chloroform have no measurable effect on the magnitude of the proton electrochemical potential, delta mu H. In the absence of EGTA these anesthetics have a small effect on delta mu H, apparently due to stimulation of Ca2+ cycling. Under these conditions the membrane potential is decreased while delta pH is increased, but the total value of delta mu H is only slightly decreased. The uncoupling activity of the anesthetics is the same in the presence of absence of EGTA. Thus, in contrast to protonophoric uncouplers, the uncoupling effect of general anesthetics does not depend on the collapse of delta mu H. In the same concentration range in which anesthetics uncouple oxidative phosphorylation both halothane and chloroform increase membrane fluidity, as measured by the partitioning of the hydrophobic spin probe 5-doxyldecane. These findings suggest a role for intramembrane processes in energy conversion that is not dependent on the bulk delta mu H.
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PMID:Uncoupling of oxidative phosphorylation in rat liver mitochondria by general anesthetics. 657 86

Subunit c of the Escherichia coli F1F0-ATPase, purified in chloroform/methanol (2:1), was reconstituted with detergent-solubilized F0 subunits a and b to form a functionally active H+ channel. The rates of H+ uptake by the proteoliposomes containing the reconstituted F0 complex were comparable to those observed with native F0 reconstituted without subunit dissociation. The F0 reconstituted from purified subunits was also shown to form an active ATP-driven H+ pump upon binding of the F1-ATPase sector of the complex. Reconstitution of D61N and D61G mutant c subunits with wild-type subunits a and b produced an inactive F0. Hybrid F0 complexes, formed with mixtures of wild-type and D61N or D61G mutant c subunits, were also prepared. Formation of an active F0 was prevented by addition of relatively small proportions of D61N or D61G mutant c subunits, i.e. active F0 formation was gradually disrupted as the mutant/wild-type ratio was increased from 0.05 to 0.2. The hybrid reconstitution studies support a model where inactivation of one of the 9-12 c subunits found in F0 is sufficient to abolish activity.
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PMID:Reconstitution of the Fo complex of Escherichia coli ATP synthase from isolated subunits. Varying the number of essential carboxylates by co-incorporation of wild-type and mutant subunit c after purification in organic solvent. 758 91

Purified subunit c from the H(+)-transporting F1F0 ATP synthase of Escherichia coli folds as an antiparallel pair of extended helices in a solution of chloroform-methanol-water. A similar hairpin-like folding is predicted for the native protein in the multisubunit transmembrane Fo sector of the ATP synthase. A single Cys variant (A67C) of subunit c was created and modified with a maleimido-PROXYL [[3-(maleimidomethyl)-2,2,5,5-tetramethyl-1-pyrrolidinyl]oxy] spin label. Pairs of 1H 2D correlation and NOE spectra were collected with the nitroxide oxidized (paramagnetic) and reduced (diamagnetic). The pairs of spectra were subtracted, yielding difference spectra containing only cross-peaks from 1H within 15 A of the spin label. These greatly simplified spectra were easily analyzed to provide complete assignments for residues 10-25 and 52-79 of the protein, 150 NOE distance restraints, and 27 hydrogen-bonding restraints. The chemical shifts and NOE patterns observed in the derivatized mutant were virtually identical to those which were resolved in the unmodified wild-type protein, strongly suggesting that the spin label was not perturbing the protein structure. The restaints enabled us to calculate a detailed structure for this region of subunit c. The structure consisted of two gently curved helices, crossing at a slight (30 degrees) angle. The C-terminal helix was disrupted from Val60 to Ala62 near the essential Pro64. Asp61, the residue thought to undergo protonation--deprotonation with each H+ transported across the membrane, was in ver der Waals contact with Ala24. The proximity of these residues had been predicted from mutant analyses, where H+ translocation was retained on moving the Asp from position 61 to 24.
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PMID:Determination of local protein structure by spin label difference 2D NMR: the region neighboring Asp61 of subunit c of the F1F0 ATP synthase. 784 23

A molecular genetic approach has been used to test the proposition that the central hydrophobic domain of yeast mitochondrial ATP synthase subunit 8 represents a transmembrane stem in contact with the lipid bilayer. The rationale for this approach is the general inability of membrane bilayers to accomodate unshielded charged residues of polypeptide chains. Non-polar residues at several positions within the central hydrophobic domain of subunit 8 were replaced with the positively charged amino acid lysine. This was done in an attempt to disrupt subunit 8 function, and thereby determine the boundaries of the putative transmembrane stem. Each subunit 8 variant was allotopically expressed in vivo as a mitochondrial import precursor encoded by a nuclear gene. It was found that all variants, which included proteins carrying two lysines at various positions in the hydrophobic domain, exhibited the ability to restore growth of subunit-8-deficient cells on the non-fermentable substrate ethanol. This indicated that the function of none of these subunit 8 variants was severely compromised. There was also no detectable change in the proteolipid characteristics of subunit 8, as defined by the chloroform/methanol solubility properties of variant proteins extracted from membranes following import into isolated mitochondria. These data suggest that subunit 8 is located in a hydrophobic niche in the mitochondrial ATP synthase, probably in contact with other protein subunits of the complex. We conclude that the function of subunit 8 does not necessarily require it to be integrated within the inner mitochondrial membrane, in contact with the lipid bilayer. Our findings also suggest that hydropathy plots, indicating hydrophobic domains within polypeptides, cannot reliably be interpreted as transmembrane helices in the absence of independent evidence.
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PMID:Relationship of subunit 8 of yeast ATP synthase and the inner mitochondrial membrane. Subunit 8 variants containing multiple lysine residues in the central hydrophobic domain retain function. 786 34

Subunit c of the H(+)-transporting F1F0 ATP synthase (EC 3.6.1.34) is thought to fold across the membrane as a hairpin of two alpha-helices and function as a key component of the H(+)-translocase of F0. We report here the initial results of a structural study of purified subunit c in a chloroform-methanol-water (4:4:1) solvent mixture using standard two-dimensional NMR techniques. The spin systems of 78 of the 79 amino acid side chains have been assigned to residue type, and 44 of these have been assigned to specific residues in the sequence. Stretches of alpha-helical secondary structure were observed for Asp7-ILe26 in the first proposed transmembrane helix, and for Arg50-Ile55 and Ala67-Val78 in the second proposed transmembrane helix. Nuclear Overhauser effects (NOEs) were observed between residues at both ends of the predicted transmembrane helices. The intensities of the NOEs between helix-1 and helix-2 were not diminished by mixing of 2H-subunit c with 1H-subunit c, and therefore the NOEs must be due to intramolecular, rather than intermolecular, interactions. Hence the purified protein must fold as a hairpin in this solvent system, just as it is thought to fold in the lipid bilayer of the membrane. In native F0, dicyclohexylcarbodiimide reacts specifically with Asp61 in the second transmembrane helix of subunit c, and the rate of this reaction is reduced by substitution of Ile28 by Thr on the first transmembrane helix. The I28T substitution is shown here to alter the chemical shifts of protons at and around Asp61. This observation provides a further indication that subunit c may fold in chloroform-methanol-water solvent much like it does in the membrane.
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PMID:Helical structure and folding of subunit c of F1F0 ATP synthase: 1H NMR resonance assignments and NOE analysis. 821 94

An ATP synthase has been isolated from green nonsulfur photosynthetic bacterium Chloroflexus aurantiacus, a representative of a lower branch of eubacteria. The enzyme, reconstituted with the bacterial lipids into proteoliposomes, is shown to catalyze [32P]Pi-ATP exchange (at a rate of 180 nmol [32P]ATP/min/mg). The ATP synthase is composed of nine polypeptide species (60, 50, 33, 19, 16.5, 15.5, 14.5, 13, and 8 kDa as determined by urea-SDS-PAGE). The catalytic part of the ATP synthase (which is detached by chloroform treatment) contains the first four polypeptides. In the intact ATP synthase the 14.5 and 13 kDa polypeptides are connected by disulfide bonds to form a heterodimer of 25 kDa.
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PMID:Subunit structure of ATP synthase from Chloroflexus aurantiacus. 824 72

Subunit c from the F1Fo ATP synthase of Escherichia coli folds in a hairpinlike structure of two alpha-helices in a solution of chloroform-methanol-H2O, and thus resembles the structure predicted for the folded protein in the membrane. The relevance of the structure in solution to the native structure was demonstrated. Asp61 in the second helical arm was shown to retain its unique reactivity with dicyclohexylcarbodiimide (DCCD) in chloroform-methanol-H2O solution. Further, the protein purified from the Ile28-->Thr DCCD-resistant mutant proved to be less reactive with DCCD in solution. This suggested that the protein folded with Ile28 of the first helical arm close to Asp61 in the second helical arm. Subunit c in wild-type E. coli membranes was specifically labeled with a nitroxide analog of DCCD (NCCD), and the derivative protein was purified. DQF COSY spectra were recorded, and the distances between the paramagnetic nitroxide and resolved protons in the spectra were calculated based upon paramagnetic broadening of the 1H resonances. The paramagnetic contribution to T2 relaxation in the NCCD-labeled sample was calculated by an iterative computer-fitting method, where a control spectrum of a phenylhydrazine-reduced sample was broadened until the line shape of one-dimensional slices through each COSY cross-peak maximally mimicked the line shape of the paramagnetic sample. The distances calculated from paramagnetic broadening indicate that Ala24 and Ala25 in helix-1 lie close (ca. 12 A) to the derivatized Asp61 in helix-2. A model for the interaction of helices in the NCCD-modified protein was generated by restrained molecular mechanics and molecular dynamics using 25 distances of < 10-20 A derived from paramagnetic broadening in combination with 15 long-range nuclear Overhauser enhancement (NOE) restraints (2-5 A) for distances between helices and the 89 intrahelical NOEs that defined helical structure in the DCCD-modified protein.
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PMID:Hairpin folding of subunit c of F1Fo ATP synthase: 1H distance measurements to nitroxide-derivatized aspartyl-61. 829 94

Subunit c of the H(+)-transporting F1Fo ATP synthase (EC 3.6.1.34) is thought to fold across the membrane as a hairpin of two alpha helices with a conserved Asp/Glu residue, centered in the second membrane-spanning helix, which is thought to function in H+ translocation. NMR studies indicate that the purified subunit c from Escherichia coli is also folded as a hairpin in a chloroform/methanol/H2O (4:4:1) solvent mixture [Girvin, M. E., & Fillingame, R. H. (1993) Biochemistry 32, 12167-12177] and that the conserved Asp remains uniquely reactive in this solvent mixture [Girvin, M. E., & Fillingame, R. H. (1994) Biochemistry 33, 665-674]. The pKa of Asp61 is of interest because of its unique reactivity and because it is thought to protonate and deprotonate during each proton translocation cycle. We have determined the pKa value of the carboxyl group of the functional Asp in wild type and two functional, mutant subunit c proteins, i.e. the Ala24-->Asp (D24D61) and the Ala24-->Asp/Asp61-->Asn (D24N61) mutant proteins. The pKa values were determined by 1H NMR spectroscopy by measuring changes in the alpha and beta proton chemical shifts by constant time two-dimensional (2D) correlated spectroscopy. The pKa of Asp61 in the purified wild type protein was 7.1. This pKa was significantly higher than the pKa of the other two Asp residues, i.e. Asp7 and Asp44 which were 5.4 and 5.6, respectively. The pKa of the two Glu residues in the protein were determined by 2D total correlation spectroscopy and found to be approximately 5.5.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Proton-translocating carboxyl of subunit c of F1Fo H(+)-ATP synthase: the unique environment suggested by the pKa determined by 1H NMR. 851 76


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