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)

The interaction of nucleotides and nucleotide analogues and their metal complexes with Mn2+ bound to both the latent and dithiothreitol-activated CF1 ATP synthase has been examined by means of steady-state kinetics, water proton relaxation rate (PRR) measurements, and 1H and 31P nuclear relaxation measurements. Titration of both the latent and activated Mn(2+)-CF1 complexes with ATP, ADP, Pi, Co(NH3)4ATP, Co(NH3)4ADP, and Co(NH3)4AMPPCP leads to increases in the water relaxation enhancement, consistent with enhanced metal binding and a high ternary complex enhancement. Steady-state kinetic studies are consistent with competitive inhibition of CF1 by Co(NH3)4AMPPCP with respect to CaATP. The data are consistent with a Ki for Co(NH3)4AMPPCP of 650 microM, in good agreement with a previous Ki of 724 microM for Cr(H2O)4ATP [Frasch, W., & Selman, B. (1982) Biochemistry 21, 3636-3643], and a best fit KD of 209 microM from the water PRR measurements. 1H and 31P nuclear relaxation measurements in solutions of CF1 and Co(NH3)4AMPPCP were used to determine the conformation of the bound substrate analogue and the arrangement with respect to this structure of high- and low-affinity sites for Mn2+. The bound nucleotide analogue adopts a bent conformation, with the low-affinity Mn2+ site situated between the adenine and triphosphate moieties and the high-affinity metal site located on the far side of the triphosphate chain. The low-affinity metal forms a distorted inner-sphere complex with the beta-P and gamma-P of the substrate. The distances from Mn2+ to the triphosphate chain are too large for first coordination sphere complexes but are appropriate for second-sphere complexes involving, for example, intervening hydrogen-bonded water molecules or residues from the protein.
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PMID:1H and 31P nuclear magnetic resonance and kinetic studies of the active site structure of chloroplast CF1 ATP synthase. 214 32

Previous studies have shown that the initial complex formed when ADP binds to nucleotide-depleted F1-ATPase is transformed with a half time of 2 to 3 min to form with a much lower rate of ADP release. The ADP binding results in a strong inhibition of ATPase activity. The present paper reports appraisal of where the inhibitory ADP binds by use of the photoreactive ADP analog, 2-N3-ADP. In presence of Mg2+ the 2-N3-ADP like ADP induces reversible inhibition of nucleotide-depleted F1 (ndF1) with a Kd of about 10 nM. Photoirradiation of the inactive 2-N3-[beta-32P]ADP-ndF1 complex results in labeling of only the beta-subunit. The major labeled peptide isolated from a trypic digest consists of residues from Ala-338 to Arg-356, with Tyr-345 as the site of labeling. This identifies the site of the inhibitory ADP binding as one of the catalytic sites of the enzyme.
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PMID:The ADP that binds tightly to nucleotide-depleted mitochondrial F1-ATPase and inhibits catalysis is bound at a catalytic site. 214 75

It is shown that ATP dissociates very slowly (koff less than 6.4 x 10(5) s-1, t1/2 greater than 3 h) from the three noncatalytic sites of E. coli F1-ATPase and that ADP dissociates from these three sites in a homogeneous fashion with koff = 1.5 x 10(-4) s-1 (t1/2 = 1.35 h). Mutagenesis of alpha-subunit residues R171 and Q172 in the 'glycine-rich loop' (Homology A) consensus region of the noncatalytic sites was carried out to test the hypothesis that unusually bulky residues at these positions are responsible wholly or partly for the observed tight binding of adenine nucleotides. The mutations alpha Q172G or alpha R171S,Q172G had no effects on ATP or ADP binding to or rates of dissociation from F1 noncatalytic sites. KdATP and KdADP of isolated alpha-subunit were weakened by approximately 1 order of magnitude in both mutants. The results suggest that neither residue alpha R171 nor alpha Q172 interacts directly with bound nucleotide, and show that the presence of bulky residues per se in the glycine-rich loop region of F1-alpha-subunit is not responsible for tight binding in the noncatalytic sites.
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PMID:Tight ATP and ADP binding in the noncatalytic sites of Escherichia coli F1-ATPase is not affected by mutation of bulky residues in the 'glycine-rich loop'. 214 65

The F1-ATPase from chloroplasts (CF1) lacks catalytic capacity for ATP hydrolysis if ATP is not bound at noncatalytic sites. CF1 heat activated in the presence of ADP, with less than one ADP and no ATP at non-catalytic sites, shows a pronounced lag in the onset of ATP hydrolysis after exposure to 5-20 microM ATP. The onset of activity correlates well with the binding of ATP at the last two of the three noncatalytic sites. The dependence of activity on the presence of ATP at non-catalytic sites is shown at relatively low or high free Mg2+ concentrations, with or without bicarbonate as an activating anion, and when the binding of ATP at noncatalytic sites is slowed 3-4-fold by sulfate. The latent CF1 activated by dithiothreitol also requires ATP at noncatalytic sites for ATPase activity. A similar requirement by other F1-ATPases and by ATP synthases seems plausible.
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PMID:ATP binding at noncatalytic sites of soluble chloroplast F1-ATPase is required for expression of the enzyme activity. 214 60

We show that a synthetic peptide corresponding to the N-terminal 22 residues of the cytochrome c oxidase subunit IV presequence blocked import of pre-subunit IV into yeast mitochondria. The 22-residue peptide pL4-(1-22) did not alter the electrical potential across the mitochondrial inner membrane (the delta psi). Inhibition of import was reversible and could be overcome by the addition of increased amounts of precursor. Two other peptides, pL4-(1-16) and pL4-(1-23), which correspond to, respectively, the N-terminal 16 and 23 residues of the same presequence, also blocked import of pre-subunit IV. However, pL4-(1-16) was a much weaker inhibitor of import, while the inhibitory effect of pL4-(1-23) was due to its ability to completely collapse the delta psi. pL4-(1-22) seems to be a general inhibitor of mitochondrial import, in that it also blocked uptake of several other proteins. These included the precursors of the yeast proteins cytochrome c oxidase subunit Va, the F1-ATPase beta subunit, mitochondrial malate dehydrogenase, and the ATP/ADP carrier. In addition, uptake of two non-yeast precursor proteins (human ornithine transcarbamylase and a cytochrome oxidase subunit IV-dihydrofolate reductase fusion), was also blocked by the peptide. Subsequent studies revealed that pL4-(1-22) did not block the initial recognition or binding of proteins to mitochondria. Rather, our results suggest that the peptide acts at a subsequent translocation step which is common to the import pathways of many different precursor proteins.
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PMID:A synthetic presequence reversibly inhibits protein import into yeast mitochondria. 216 Apr 69

Several mutants of yeast lacking the porin gene have been found stable and viable on glucose or glycerol media. Ethanol-supported respiration of porin-free mutant and wild cells appeared equally coupled in vivo being similarly depressed by inhibitors of ADP/ATP translocase or of ATP synthase and stimulated by the uncoupler FCCP. The absence of porin in isolated mutant mitochondria hardly impaired the electron flux but increased the requirement for Mg2+ (or Ca2+) and for ADP and carboxyatractylate concentrations necessary to drive effectively state 3 - state 4 and state 4 - state 3 transitions, respectively. The existence of another porin species, possibly controlled by bivalent cations, is postulated.
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PMID:The respiration of cells and mitochondria of porin deficient yeast mutants is coupled. 216 77

The yeast mitochondrial outer membrane contains a major 70 kd protein with an amino-terminal hydrophobic membrane anchor and a hydrophilic 60 kd domain exposed to the cytosol. We now show that this protein (which we term MAS70) accelerates the mitochondrial import of many (but not all) precursor proteins. Anti-MAS70 IgGs or removal of MAS70 from the mitochondria by either mild trypsin treatment or by disrupting the nuclear MAS70 gene inhibits import of the F1-ATPase beta-subunit, the ADP/ATP translocator, and of several other precursors into isolated mitochondria by up to 75%, but has little effect on the import of porin. Intact cells of a mas70 null mutant import the F1-ATPase alpha-subunit and beta-subunits, cytochrome c1 and other precursors at least several fold more slowly than wild-type cells. Removal of MAS70 from wild-type mitochondria inhibits binding of the ADP/ATP translocator to the mitochondrial surface, indicating that MAS70 mediates one of the earliest import steps. Several precursors are thus imported by a pathway in which MAS70 functions as a receptor-like component. MAS70 is not essential for import of these precursors, but only accelerates this process.
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PMID:Protein import into yeast mitochondria is accelerated by the outer membrane protein MAS70. 217 Jan 6

The process of ATP or GTP synthesis by bovine heart submitochondrial particles involves the binding of ADP or GDP to 3 exchangeable sites I, II, and III, and only upon substrate occupation of site III does rapid ATP or GTP synthesis take place. The dissociation constants determined for ADP were KADPI less than or equal to 10(-8) M, KADPII approximately 10(-7) M, and KADPIII (equivalent to apparent KADPm), approximately 3 x 10(-6) M in the low Km mode and KADPIII approximately 150 x 10(-6) M in the high Km mode. For GDP, these constants were KGDPI approximately 10(-6)-10(-5) M, KGDPII approximately 10(-4) M, and KGDPIII approximately 10(-3) M when NADH was the respiratory substrate (Matsuno-Yagi, A., and Hatefi, Y. (1990) J. Biol. Chem. 265, 82-88). Because of its low affinity for the above binding sites, GDP at micromolar concentrations does not lead to GTP synthesis. However, as shown in this paper, micromolar [GDP] undergoes phosphorylation in the presence of micromolar concentrations of ADP. Under these conditions, both ATP and GTP are synthesized. GDP inhibits ATP synthesis with KGDPi congruent to 7 microM, while ADP promotes GTP synthesis in a reaction that requires inorganic phosphate (apparent KPim = 2-3 mM) and is inhibited by uncouplers and inhibitors of the ATP synthase complex. The ADP-promoted GTP synthesis exhibited an "apparent" KGDPm = 4 microM and an "apparent" Vmax = 11 nmol of GTP (min.mg of protein)-1. These results were interpreted to mean that (a) micromolar [ADP] occupies sites I and II, allowing site III to bind and phosphorylate GDP, and (b) the KGDPm and Vmax calculated under these conditions represent values for the low Km-low Vmax mode of GTP synthesis, which in the absence of ADP is not detectable because of the positive cooperativity phase of GTP synthesis with the high KGDPII approximately 10(-4) M.
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PMID:Studies on the mechanism of oxidative phosphorylation. ADP promotion of GDP phosphorylation. 224 94

Oxidative phosphorylation can be treated as two groups of reactions; those that generate protonmotive force (dicarboxylate carrier, succinate dehydrogenase and the respiratory chain) and those that consume protonmotive force (adenine nucleotide and phosphate carriers. ATP synthase and proton leak). Mitochondria from hypothyroid rats have lower rates of respiration in the presence of ADP (state 3) than euthyroid controls. We show that the kinetics of the protonmotive-force generators are unchanged in mitochondria from hypothyroid animals, but the kinetics of the protonmotive-force consumers are altered, supporting proposals that the important effects of thyroid hormone on state 3 are on the ATP synthase or the adenine nucleotide translocator.
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PMID:Thyroid-hormone control of state-3 respiration in isolated rat liver mitochondria. 230 10

The precursors of the mitochondrial proteins ADP/ATP carrier (AAC) and F1-ATPase subunit beta (F1 beta) were accumulated at the stages of binding to receptor sites on the mitochondrial outer membrane, or in contact sites between outer and inner membranes. Specific antibodies raised against the mature proteins were added to the isolated mitochondria and efficiently bound to these translocation intermediates. Further movement of the precursors to consecutive steps along their import pathway was thereby inhibited. Controls showed that precursor proteins which were inserted into or translocated across the outer membrane were not recognized by the antibodies unless the mitochondrial membranes were disrupted. We conclude that the trapped translocation intermediates have antigenic sites exposed to the outside of the outer membrane.
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PMID:Mitochondrial protein import: differential recognition of various transport intermediates by antibodies. 245 44


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