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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. In the accompanying paper (Duchen & Biscoe, 1992) we have described graded changes in autofluorescence derived from mitochondrial NAD(P)H in type I cells of the carotid body in response to changes of PO2 over a physiologically significant range. These observations suggest that mitochondrial function in these cells is unusually sensitive to oxygen and could play a role in oxygen sensing. We have now explored further the relationships between hypoxia, mitochondrial membrane potential (delta psi m) and [Ca2+]i. 2. The fluorescence of Rhodamine 123 (Rh 123) accumulated within mitochondria is quenched by delta psi m. Mitochondrial depolarization thus increases the fluorescence signal. Blockade of electron transport (CN-, anoxia, rotenone) and uncoupling agents (e.g. carbonyl cyanide p-trifluoromethoxy-phenylhydrazone; FCCP) increased fluorescence by up to 80-120%, while fluorescence was reduced by blockade of the F0 proton channel of the mitochondrial ATP synthase complex (oligomycin). 3. delta psi m depolarized rapidly with anoxia, and was usually completely dissipated within 1-2 min. The depolarization of delta psi m with anoxia (or CN-) and repolarization on reoxygenation both followed a time course well characterized as the sum of two exponential processes. Oligomycin (0.2-2 micrograms/ml) hyperpolarized delta psi m and abolished the slower components of both the depolarization with anoxia and of the subsequent repolarization. These data (i) illustrate the role of the F1-F0 ATP synthetase in slowing the rate of dissipation of delta psi m on cessation of electron transport, (ii) confirm blockade of the ATP synthetase by oligomycin at these concentrations, and (iii) indicate significant accumulation of intramitochondrial ADP during 1-2 min of anoxia. 4. Depolarization of delta psi m was graded with graded changes in PO2 below about 60 mmHg. The stimulus-response curves thus constructed strongly resemble those for [Ca2+]i and NAD(P)H with PO2. The change in delta psi m closely followed changes in PO2 with time. 5. The rate of rise of [Ca2+]i in response to anoxia is strongly temperature sensitive. The rate of depolarization of delta psi m with anoxia similarly increased at least two- to fivefold on warming from 22 to 36 degrees C. The change with FCCP was not significantly altered by temperature. 6. These data show that the mitochondrial membrane potential changes over a physiological range of PO2 values in type I cells. This contrasts with the behaviour in dissociated chromaffin cells and sensory neurons, in which no change was measurable until the PO2 fell close to zero.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Relative mitochondrial membrane potential and [Ca2+]i in type I cells isolated from the rabbit carotid body. 143 12

The a subunit, a membrane protein from the E. coli F1F0 ATP synthase has been examined by Fourier analysis of hydrophobicity and of amino-acid residue variation. The amino-acid sequences of homologous subunits from Vibrio alginolyticus, Saccharomyces cerevisiae, Neurospora crassa, Aspergillus nidulans, Schizosaccharomyces pombe and Candida parapsilosis were used in the variability analysis. By Fourier analysis of sequence variation, two transmembrane helices are predicted to have one face in contact with membrane lipids, while the other spans are predicted to be more shielded from the lipids by protein. By Fourier analysis of hydrophobicity, six amphipathic alpha-helical segments are predicted in extra-membrane regions, including the region from Glu-196 to Asn-214. Fourier analysis of sequence variation in the b- and the c-subunits of the Escherichia coli F1F0 ATP synthase indicates that the single transmembrane span of the b-subunit and the C-terminal span of the c subunit each have a face in contact with membrane lipids. On the basis of this analysis topographical models for the a- and c-subunits and for the F0 complex are proposed.
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PMID:Prediction of transmembrane topology of F0 proteins from Escherichia coli F1F0 ATP synthase using variational and hydrophobic moment analyses. 144 40

The genes encoding body-wall-specific glyceraldehyde-3-phosphate dehydrogenase from Caenorhabditis briggsae were sequenced and compared to the homologous genes from Caenorhabditis elegans. The direct tandem organization of these genes, gpd-2 and gpd-3, and the size and location of the two introns in each gene are the same in C. elegans and C. briggsae. Primer-extension studies demonstrated that the two genes in C. briggsae are trans-splice differentially with the same splice leader (SL) RNAs as are observed in C. elegans. The gdp-2 gene is trans-spliced with SL1 while gdp-3 is trans-spliced with SL2. Significant sequence conservation was observed within the promoter regions of each species and may indicate those regions responsible for body-wall-muscle-specific gene expression and/or differential trans-splicing. Comparisons of the sequences suggest that the tandem repeat of the genes has been subjected to concerted evolution and that C. briggsae and C. elegans diverged much earlier than would be anticipated based on morphological similarities alone. Finally, an open reading frame found several hundred nucleotides upstream from gpd-2, in both species, appears to be homologous to the ATP synthase subunit, ATPase inhibitor protein, from bovine mitochondria.
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PMID:Conservation of gene organization and trans-splicing in the glyceraldehyde-3-phosphate dehydrogenase-encoding genes of Caenorhabditis briggsae. 144 20

The DNA of subunit II of the H(+)-ATPase from spinach chloroplast was expressed in Escherichia coli. It was found that a high gene dose is lethal to E. coli. With a lower gene dose subunit II was not able to substitute for the homologous subunit b in the E. coli ATP synthase.
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PMID:Expression of subunit II of chloroplast H(+)-ATPase in an Escherichia coli mutant lacking subunit b of its H(+)-ATPase. 144 71

A cDNA clone encoding the complete precursor of the gamma subunit of the pea chloroplast ATP synthase has been isolated from a pea leaf cDNA library in lambda gt 11 following detection with antibodies to the purified gamma subunit. The cDNA insert of 1.4 kbp is smaller than transcripts of about 1.6 kb detected by northern hybridisation of RNA from both light- and darkgrown pea leaves. The cDNA encodes a polypeptide of 376 amino acid residues, of which 52 residues constitute an N-terminal presequence and 324 residues make up the mature protein. Transcription and translation of the cDNA in vitro produced a protein of 42 kDa, which was imported by isolated pea chloroplasts and processed to the mature 36 kDa subunit.
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PMID:Chloroplast import of the precursor of the gamma subunit of pea chloroplast ATP synthase. 145 Mar 88

Methanogenesis is restricted to a group of prokaryotic microorganisms which thrive in strictly anaerobic habitats where they play an indispensable role in the anaerobic food chain. Methanogenic bacteria possess a number of unique cofactors and coenzymes that play an important role in their specialized metabolism. Methanogenesis from a number of simple substrates such as H2 + CO2, formate, methanol, methylamines, and acetate is associated with the generation of transmembrane electrochemical gradients of protons and sodium ions which serve as driving force for a number of processes such as the synthesis of ATP via an ATP synthase, reverse electron transfer, and solute uptake. Several unique reactions of the methanogenic pathways have been identified that are involved in energy transduction. Their role and importance for the methanogenic metabolism are described.
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PMID:Energetics of methanogenesis studied in vesicular systems. 145 85

Photophosphorylation in halobacteria is carried out by two rather simple elements: an A-type ATP synthase and light-driven ion-pumping bacterial rhodopsins. The unique features of halobacterial ATP synthase, mostly common to archaebacteria (A-type), and of new members of the bacteriorhodopsin family are introduced along with studies performed in the authors' laboratory. This is the story of how we found that the A-type ATP synthase is close to V-type ATPase but far from F-type ATPase, although all three ATPases are believed to have the same ancestor. Archaerhodopsins, the new members of the proton-pumping retinal proteins, were found in Australian halobacteria and have been used in a comparative study of bacterial rhodopsins.
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PMID:Photophosphorylation elements in halobacteria: an A-type ATP synthase and bacterial rhodopsins. 145 86

Subunit e of H(+)-ATP synthase from rat liver mitochondria was isolated from the purified enzyme by reverse-phase high-performance liquid chromatography. The amino acid sequence of the subunit was determined by automated Edman degradation of the whole protein and derived peptides. The nucleotide sequence of the import precursor of subunit e of rat liver H(+)-ATP synthase was determined from a recombinant cDNA clone isolated by screening a rat hepatoma cell line H4TG cDNA library with a probe DNA. The sequence was composed of 289 nucleotides including a coding region for the import precursor of subunit e and noncoding regions on the 5'- and 3'-sides. The possible import precursor of subunit e and its mature polypeptide deduced from the open reading frame consisted of 71 and 70 amino acid residues with molecular weights of 8254 and 8123, respectively. Subunit e is a basic hydrophilic protein with an isoelectric point of 9.78. The sequence of the rat subunit e is highly homologous with that of subunit e of bovine heart, but has no homology with any subunit of bacterial or chloroplast H(+)-ATP synthase. The function of subunit e is unknown. However, a homology search in the database of the National Biomedical Research Foundation revealed that residues 34-65 of subunit e are homologous with residues 90-117 of troponin T, and with residues 529-561 of h-caldesmon and residues 289-319 of l-caldesmon, which are the homologous sequences corresponding to the Ca(2+)-dependent tropomyosin-binding region of troponin T.
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PMID:Complete amino acid sequence of subunit e of rat liver mitochondrial H(+)-ATP synthase. 146 32

Yeast Saccharomyces cerevisiae oligomycin sensitivity conferring proteins (OSCP) have been expressed in Escherichia coli. Heterologous expression results in production of a protein that is identical to yeast mature OSCP, including the absence of the initiating methionine residue. Yeast OSCP expressed in E. coli has been purified to homogeneity and it is able to reconstitute oligomycin-sensitive ATPase using purified F1- and F1/OSCP-depleted membranes (electron transport particles (ETP). Binding of F1 to ETP is dependent on the addition of OSCP. Binding studies using 35S-OSCP indicated that OSCP binds to ETP with a Kd of 200 nM and a capacity of 420 pmol/mg particle protein, whereas OSCP does not interact with F1 in the absence of ETP. These data indicate that yeast OSCP must first form a specific complex with F0, which then binds F1 forming the functional complex. To identify functional domains in yeast OSCP, two deletion mutants have been made. Antibodies directed to these deletion products do not inhibit OSCP-dependent binding of F1 to ETP. However, antibodies directed against the last one-third of OSCP greatly reduce the oligomycin sensitivity of the reconstituted ATPase. These data suggest that OSCP is involved in a functional role in energy transduction or proton translocation and serves a structural role in the yeast mitochondrial ATP synthase.
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PMID:Heterologous expression, purification, and biochemistry of the oligomycin sensitivity conferring protein (OSCP) from yeast. 146 86

Many parasitic protozoa go through complex life cycles in the course of which they adapt to widely different environments; ion transport processes are expected to play a role both in pathogenicity and in adaptation. So far, studies on ion transport have been virtually limited to Leishmania, Plasmodium and Entamoeba. The distribution of ion pumps in the former two organisms generally appears to conform to the picture established for other protozoa, i.e. a proton-motive P-ATPase in the plasma membrane provides the driving force for H(+)-coupled secondary-active transport, a proton-motive V-ATPase in the digestive vacuoles is responsible for vacuolar acidification, and an F-ATPase (ATP synthase) is found in the mitochondria. The situation in Entamoeba, an archaic organism that lacks mitochondria, could be different from that in the two other parasites in that a V-ATPase may be present and active both in the plasma membrane and in the membranes of the endocytic vesicles.
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PMID:Ion transport in parasitic protozoa. 149 Dec 29


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