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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)

Preparations enriched in Chlamydomonas reinhardtii thylakoids have proven useful in the study of photosynthesis. Many of their polypeptides however remain unidentified. We report here on three of those, h1 (34 kDa), h2 (11 kDa), and P3 (63 kDa). h1, h2, and P3 are present in all tested mutants of C. reinhardtii lacking either one or several of the photosynthetic chain complexes or depleted in thylakoid membranes. h2 is an ascorbate-reducible, soluble c550-type cytochrome encoded in the nucleus. It cross-reacts immunologically with mitochondrial cytochromes c from various sources and contains a hexapeptide encoded in C. reinhardtii cytochrome c cDNA. P3, a nuclear-encoded peripheral protein, cross-reacts with various ATP synthase beta subunits. Its N-terminal sequence is encoded in C. reinhardtii mitochondrial beta subunit cDNA. h1 behaves as an integral hemoprotein; it is absent in a mitochondrial mutant that carries a deletion in apocytochrome b gene. We conclude that C. reinhardtii mitochondrial membranes copurify with thylakoid membranes. h1 is part of the cytochrome bc1 complex, h2 is cytochrome c, and P3 is the beta subunit of mitochondrial ATP synthase.
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PMID:Identification of mitochondrial proteins in membrane preparations from Chlamydomonas reinhardtii. 130 33

Steady-state levels of the mitochondrial rRNAs, of mRNAs for mitochondrially and nuclear-encoded subunits of cytochrome c oxidase and for the beta subunit of ATP synthase were assessed by Northern blot hybridizations during the in vitro differentiation of human myoblasts. Transcript levels of the so-called liver-type form of subunit VIa of cytochrome c oxidase diminished during the course of differentiation, while transcription of the so-called heart-type form was induced. Transcripts for the liver-type form and for the heart-type form of subunit VIIa of cytochrome c oxidase were detected in all myogenic cultures; the levels of the heart-type form progressively increased during the course of differentiation. The levels of the other transcripts studied did not change substantially. The results suggest subunit switching of subunit VIa and co-expression of subunit VIIa isoforms during myogenesis. The differential changes in mRNA levels of the heart-type subunits VIa and VIIa and the differential changes in mRNA levels of the liver-type subunits VIa and VIIa demonstrate that different transcriptional regulation mechanisms are present for both heart-type genes as well as for both liver-type genes.
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PMID:Steady-state transcript levels of cytochrome c oxidase genes during human myogenesis indicate subunit switching of subunit VIa and co-expression of subunit VIIa isoforms. 131 12

We provide experimental support for the proposal that ATP production in Methanococcus voltae, a methanogenic member of the archaea, is based on an energetic system in which sodium ions, not protons, are the coupling ions. We show that when grown at a pH of 6.0, 7.1, or 8.2, M. voltae cells maintain a membrane potential of approximately -150 mV. The cells maintain a transmembrane pH gradient (pH(in) - pH(out)) of -0.1, -0.2, and -0.2, respectively, values not favorable to the inward movement of protons. The cells maintain a transmembrane sodium concentration gradient (sodium(out)/sodium(in)) of 1.2, 3.4, and 11.6, respectively. While the protonophore 3,3',4',5-tetrachlorosalicylanilide inhibits ATP formation in cells grown at pH 6.5, neither ATP formation nor growth is inhibited in cells grown in medium at pH 8.2. We show that when grown at pH 8.2, cells synthesize ATP in the absence of a favorably oriented proton motive force. Whether grown at pH 6.5 or pH 8.2, M. voltae extrudes Na+ via a primary pump whose activity does not depend on a proton motive force. The addition of protons to the cells leads to a harmaline-sensitive efflux of Na+ and vice versa, indicating the presence of Na+/H+ antiporter activity and, thus, a second mechanism for the translocation of Na+ across the cell membrane. M. voltae contains a membrane component that is immunologically related to the H(+)-translocating ATP synthase of the archaeabacterium Sulfolobus acidocaldarius. Since we demonstrated that ATP production can be driven by an artificially imposed membrane potential only in the presence of sodium ions, we propose that ATP production in M. voltae is mediated by an Na+-translocating ATP synthase whose function is coupled to a sodium motive force that is generated through a primary Na+ pump.
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PMID:Energy transduction in the methanogen Methanococcus voltae is based on a sodium current. 132 4

The F0 sector of the ATP synthase complex facilitates proton translocation through the membrane, and via interaction with the F1 sector, couples proton transport to ATP synthesis. The molecular mechanism of function is being probed by a combination of mutant analysis and structural biochemistry, and recent progress on the Escherichia coli F0 sector is reviewed here. The E. coli F0 is composed of three types of subunits (a, b, and c) and current information on their folding and organization in F0 is reviewed. The structure of purified subunit c in chloroform-methanol-H2O resembles that in native F0, and progress in determining the structure by NMR methods is reviewed. Genetic experiments suggest that the two helices of subunit c must interact as a functional unit around an essential carboxyl group as protons are transported. In addition, a unique class of suppressor mutations identify a transmembrane helix of subunit a that is proposed to interact with the bihelical unit of subunit c during proton transport. The role of multiple units of subunit c in coupling proton translocation to ATP synthesis is considered. The special roles of Asp61 of subunit c and Arg210 of subunit a in proton translocation are also discussed.
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PMID:H+ transport and coupling by the F0 sector of the ATP synthase: insights into the molecular mechanism of function. 133 Oct 39

The beta-subunit of the mitochondrial ATP synthase complex comprises the bulk, if not all, of the catalytic nucleotide binding site on the enzyme. A region of homologous sequence rich in glycines (G) and containing a basic lysine (K) and a threonine (T) is found in the beta-subunit as well as many other purine nucleotide binding proteins. The consensus sequence of this region is Gx4GKT, where x represents any amino acid, and is called the A region or glycine-rich loop. The related function of these proteins implies that the glycine-rich loop is directly involved in nucleotide binding. Here we directly test the involvement of the beta-subunit's glycine-rich region in adenine nucleotide binding using two independent approaches. A synthetic fifty amino acid peptide, PP-50, containing the glycine-rich region and the surrounding sequence was assessed for secondary structure and interaction with potential ligands. Circular dichroism spectropolarimetry indicates that PP-50 assumes a predominantly beta-sheet conformation in solution. Significantly, the peptide precipitates from solution when ATP, ADP, GTP, ITP, and pyrophosphate are added, but not when AMP or phosphate are included. Magnesium is not required for the interaction with the purine nucleotides. Complimentary to these studies, the sequence around the Gx4GKT motif was deleted from a recombinant rat liver beta-subunit overexpressed in E. coli. While the wild type beta-subunit showed specificity for the tri- and diphosphonucleotides, the deletion mutant bound tri-, di-, and monophosphate nucleotides with equal affinity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mitochondrial F-type ATPases: the glycine-rich loop of the beta-subunit is a pyrophosphate binding domain. 133 55

Oxidative phosphorylation, which involves an exclusively proton-coupled ATP synthase, and pH homeostasis, which depends upon electrogenic antiport of cytoplasmic Na+ in exchange for H+, are the two known bioenergetic processes that require inward proton translocation in extremely alkaliphilic bacteria. Energy coupling to oxidative phosphorylation is particularly difficult to fit to a strictly chemiosmotic model because of the low bulk electrochemical proton gradient that follows from the maintenance of a cytoplasmic pH just above 8 during growth at pH 10.5 and higher. A large quantitative and variable discrepancy between the putative chemiosmotic driving force and the phosphorylation potential results. This is compounded by a nonequivalence between respiration-dependent bulk gradients and artificially imposed ones in energizing ATP synthesis, and by an apparent requirement for specific respiratory chain complexes that do not relate solely to their role in generation of bulk gradients. Special features of the synthase may contribute to the mode of energization, just as novel features of the Na+ cycle may relate to the extraordinary capacity of the extreme alkaliphiles to achieve pH homeostasis during growth at, or sudden shifts to, an external pH of 10.5 and above.
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PMID:Proton-coupled bioenergetic processes in extremely alkaliphilic bacteria. 133 72

The ATP synthase (F1Fo) of Escherichia coli consists of two structurally and functionally distinct entities. The F1 part is composed of five subunits alpha, beta, gamma, delta and epsilon (3:3:1:1:1) and carries the catalytic centres of the enzyme. The membrane-bound Fo complex functions as a proton channel and consists of the three subunits a, b and c (1:2:10 +/- 1). Subunit c (8288 M(r)) exhibits a hairpin-like structure within the membrane. A conserved acidic residue (Asp-61) in the C-terminal hydrophobic segment is absolutely required for proton translocation through Fo, whereas the hydrophilic loop region is necessary for F1 binding. Expression of the chloroplast proteolipid together with subunits a and b of E. coli did not produce an active Fo hybrid complex. Therefore, the construction of hybrid c subunits consisting of parts of the proteolipid from both organisms is in progress to determine those parts of subunit c that are essential for a functional interplay with subunits a and b. Subunit a (30,276 M(r)), which is also involved in proton translocation, is an extremely hydrophobic protein with 5-8 membrane-spanning helices. Studies with alkaline phosphatase fusion proteins resulted in controversial conclusions about the localization of the N and C termini of the protein. A foreign epitope (13 amino acids) has been inserted into the N- or C-terminal region of subunit a without affecting the function of Fo. Binding studies with a monoclonal antibody against this epitope are now under investigation to determine the orientation of subunit a.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The Fo complex of the proton-translocating F-type ATPase of Escherichia coli. 133 99

A collection of amino acid substitutions at residues Glu-32 and His-39 in the epsilon subunit of the Escherichia coli F1F0 ATP synthase has been constructed by cassette mutagenesis. Substitutions for residue Glu-32 appeared to cause abnormal inhibition of membrane-bound F1 ATPase activity, and replacement of His-39 by Arg, Val, and Pro affected F1F0 interactions.
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PMID:Mutations at Glu-32 and His-39 in the epsilon subunit of the Escherichia coli F1F0 ATP synthase affect its inhibitory properties. 134 13

We have isolated and sequenced cDNA and genomic clones encoding the alpha and beta subunits of the Neurospora crassa ATP synthase. The genes are not linked to each other: atp-1(alpha) maps to either linkage group I or V, and atp-2(beta) lies on linkage group II. The two genes resemble each other in having a large number of introns, five in atp-1 and seven in atp-2, mostly positioned near their 5' ends and varying in length from 60-332 bp. The coding regions of both genes have a high G+C content (59%) and use a low number of codons, 46 (atp-1) and 44 (atp-2), a feature associated with highly expressed genes. Northern-blot analysis shows both genes are expressed at high levels during mycelial growth. Comparison of the exon-intron structures of the beta-subunit-encoding gene with those from human and tobacco showed a similar number of introns, several closely positioned, but no exact conservation in position, size or sequence of introns.
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PMID:Structures of the genes encoding the alpha and beta subunits of the Neurospora crassa mitochondrial ATP synthase. 135 Oct 18

By use of restriction fragment length polymorphism analysis, we examined the liver mitochondrial DNA amplified by polymerase chain reaction from 60 Chinese subjects of 31 to 78 years of age. We found nine specific mtDNA polymorphisms that had never been reported before. Eleven subjects had an Alu I polymorphic site in the subunit 2 gene of NADH dehydrogenase, five had a Hae III polymorphic site in the cytochrome oxidase subunit 2 gene, and five had a Hinf I polymorphic site in the subunit 3 gene of cytochrome oxidase. No polymorphic site was found in the structural genes coding for subunits 1, 3, 4, 4L and 6 of NADH dehydrogenase, cytochrome b, and subunit 8 of ATP synthase. Detailed analysis of the RFLP data did not show age-dependent mtDNA polymorphisms. In addition, the analysis of the restriction patterns of all the mtDNAs revealed 12 mtDNA haplotypes in all the Chinese subjects examined. Among them, type 1 mtDNA was found to be the most predominant and comprised 63.3% of the total study subjects. The restriction patterns of type 1 mtDNA generated by all restriction enzymes were identical to those deduced from the Cambridge sequence of human mtDNA. About 8.3% of the subjects exhibited type 2 mtDNA, and 5% had types 3, 5 and 8 mtDNA, respectively. Each of the rest seven mtDNA types comprised about 2% of the samples. Moreover, type 1 mtDNA was found in the platelets of three white Americans. These findings suggest that type 2 to type 12 mtDNAs have come into existence through the generation or loss of specific polymorphic restriction sites in the mtDNA of the Chinese.
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PMID:Specific restriction fragment length polymorphism in liver mitochondrial DNA of the Chinese. 135 20


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