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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)

Closed protein-phospholipid particles (proteoliposomes), obtained by self-assembly method, are capable to generate and to maintain the membrane potential in the case if their protein complex is represented by: a) a complex of mitochondrial ATPase; b) a complex of cytochrome oxidase and cytochrome c and c) bacteriorhodopsin from Halobacterium halobium; and their phospholipid component is represented by phosphatidylethanolamine or by a mixture of mitochondrial phospholipids. Only cytochromoxidase and bacteriorhodopsin (but not ATPase) proteoliposomes with phosphatidylserine are active. Cardiolipin also is not active in experiments with ATPase. Phosphatidylcholine produces in all the cases proteoliposomes incapable of maintaining the membrane potential. It is concluded that the inefficiency of phosphatidylcholine in the formation of proteoliposomes, generating the membrane potential, is due to the impossibility of obtaining closed membrane forms with a high electric resistance. The inefficiency of phosphatidylserine and cardiolipine, in the case of ATPase protein component of proteoliposomes, may be due to a specific requirement of this generator of the membrane potential in phosphatidylethanolamine.
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PMID:[Role of phospholipids in the generation of membrane potentials by proteoliposomes]. 17 54

Oxidation of ferrocytochrome c by molecular oxygen catalysed by cytochrome c oxidase (cytochrome aa3) is coupled to translocation of H+ ions across the mitochondrial membrane. The proton pump is an intrinsic property of the cytochrome c oxidase complex as revealed by studies with phospholipid vesicles inlayed with the purified enzyme. As the conformation of cytochrome aa3 is specifically sensitive to the electrochemical proton gradient across the mitochondrial membrane, it is likely that redox energy is primarily conserved as a conformational "strain" in the cytochrome aa3 complex, followed by relaxation linked to proton translocation. Similar principles of energy conservation and transduction may apply on other respiratory chain complexes and on mitochondrial ATP synthase.
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PMID:The mechanism of energy conservation and transduction by mitochondrial cytochrome c oxidase. 20 Dec 86

Thyroid hormone is one of the few known physiological regulators of mammalian mitochondrial biogenesis. Although it exerts a global effect on biogenesis, it does so by regulating the expression of a limited number of unidentified mitochondrial proteins. We have investigated these hormone-regulated proteins in rat liver. Hormone injection induced a 30-fold increase in the levels of cytochrome-c1 mRNA after 3 d. In addition, the mRNA for the growth-activated adenine-nucleotide translocator, ANT2, was increased 13-fold and that for the ATPase N,N'-dicyclohexylcarbodiimide-binding protein increased 4-5-fold. Mitochondrial transcripts of cytochrome-oxidase subunit I also increased. No changes were found in the mRNA levels for the F1-ATPase beta-subunit or cytochrome oxidase IV. A single low dose of triiodothyronine induces rapid increases in cytochrome-c1 and ANT2 mRNA species which parallel changes in the activity of the hormone-responsive malic enzyme, but are earlier than other mitochondrial biogenetic events. These data strengthen the view that thyroid hormone regulates synthesis of specific components within each respiratory-chain complex and that these products apparently play key roles in inner-membrane biogenesis and assembly. The significance of ANT2 induction is also discussed with respect to the rapid respiratory response induced by thyroid hormone.
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PMID:Transcript levels for nuclear-encoded mammalian mitochondrial respiratory-chain components are regulated by thyroid hormone in an uncoordinated fashion. 132 Oct 44

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

Cells from a rapidly growing rat Zajdela hepatoma were shown to contain (on a protein basis) five-times less mitochondria than hepatocytes from resting or regenerating rat liver. Transcripts of four nuclear genes for representative mitochondrial membrane proteins (beta-F1 subunit and N,N'-dicyclohexyl-carbodiimide-binding protein of ATP synthase, subunit IV of cytochrome oxidase and ADP/ATP translocase) were present in 2-4 times higher amounts in the poly(A)-rich RNA of the hepatoma than in the corresponding RNA fraction from resting or regenerating rat liver. The liver and hepatoma transcripts for the beta-F1 subunit were translated in an in-vitro system with equal efficiency. Pulse-chase labeling of isolated Zajdela hepatoma cells and hepatocytes from resting and regenerating liver revealed a relative excess of the newly synthesized beta-F1 subunit in the tumor cells. The half-life of the beta-F1 subunit was significantly shorter in the hepatoma cells than in hepatocytes from resting and regenerating liver. The contents of transcripts of three mitochondrial genes examined (cytochrome oxidase subunits I and II and NADH-ubiquinone reductase subunit 2) in Zajdela hepatoma mitochondria were about five-times higher than in the mitochondria of the resting cells and 3-4 times higher than in the organelles of the regenerating organ. The results indicate that events other than transcription (most likely post-translational) may be responsible for the reduced content of mitochondria in tumor cells.
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PMID:Increased steady-state levels of several mitochondrial and nuclear gene transcripts in rat hepatoma with a low content of mitochondria. 137 34

Biogenesis of mammalian mitochondria requires the participation of both nuclear and mitochondrial genes. In order to study the expression and coordination of these two sets of genes, serum-deprived, quiescent NIH 3T3 cells were activated by serum addition. The steady-state levels of the transcripts for two growth-response genes (the mitochondrial adenine-nucleotide translocator and non-mitochondrial beta-actin), one nuclear-encoded respiratory-chain component (F1-ATPase beta-subunit) and the mitochondrial-encoded subunit I of cytochrome oxidase decreased significantly in quiescent cells and were rapidly restored with similar kinetics after addition of serum. The transcripts for two additional nuclear-encoded mitochondrial genes (cytochrome c1 and cytochrome oxidase subunit IV) did not respond to serum deprivation or growth activation. These results imply that mitochondrial biogenesis is at least partially regulated through growth-dependent mechanisms. Furthermore, the expression of nuclear genes encoding mitochondrial respiratory-chain components does not appear to be tightly coordinated, suggesting the existence of multiple control circuits.
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PMID:Differential regulation of the transcript levels of some nuclear-encoded and mitochondrial-encoded respiratory-chain components in response to growth activation. 137 2

Previous studies on mitochondrial targeting presequences have indicated that formation of an amphiphillic helix may be required for efficient targeting of the precursor protein into mitochondria, but the structural details are not well understood. We have used CD and NMR spectroscopy to characterize in detail the structure of a synthetic peptide corresponding to the presequence for the beta-subunit of F1-ATPase, a mitochondrial matrix protein. Although this peptide is essentially unstructured in water, alpha-helix formation is induced when the peptide is placed in structure-promoting environments, such as SDS micelles or aqueous trifluoroethanol (TFE). In 50% TFE (by volume), the peptide is in dynamic equilibrium between random coil and alpha-helical conformations, with a significant population of alpha-helix throughout the entire peptide. The helix is somewhat more stable in the N-terminal part of the presequence (residues 4-10), and this result is consistent with the structure proposed previously for the presequence of another mitochondrial matrix protein, yeast cytochrome oxidase subunit IV. Addition of increasing amounts of TFE causes the alpha-helical content to increase even further, and the TFE titration data for the presequence peptide of the F1-ATPase beta-subunit are not consistent with a single, cooperative transition from random coil to alpha-helix. There is evidence that helix formation is initiated in two different regions of the peptide. This result helps to explain the redundancy of the targeting information contained in the presequence for the F1-ATPase beta-subunit.
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PMID:Conformational analysis of a mitochondrial presequence derived from the F1-ATPase beta-subunit by CD and NMR spectroscopy. 139 Sep 13

We have seen that there is no simple answer to the question 'what controls respiration?' The answer varies with (a) the size of the system examined (mitochondria, cell or organ), (b) the conditions (rate of ATP use, level of hormonal stimulation), and (c) the particular organ examined. Of the various theories of control of respiration outlined in the introduction the ideas of Chance & Williams (1955, 1956) give the basic mechanism of how respiration is regulated. Increased ATP usage can cause increased respiration and ATP synthesis by mass action in all the main tissues. Superimposed on this basic mechanism is calcium control of matrix dehydrogenases (at least in heart and liver), and possibly also of the respiratory chain (at least in liver) and ATP synthase (at least in heart). In many tissues calcium also stimulates ATP usage directly; thus calcium may stimulate energy metabolism at (at least) four possible sites, the importance of each regulation varying with tissue. Regulation of multiple sites may occur (from a teleological point of view) because: (a) energy metabolism is branched and thus proportionate regulation of branches is required in order to maintain constant fluxes to branches (e.g. to proton leak or different ATP uses); and/or (b) control over fluxes is shared by a number of reactions, so that large increases in flux requires stimulation at multiple sites because each site has relatively little control. Control may be distributed throughout energy metabolism, possibly due to the necessity of minimizing cell protein levels (see Brown, 1991). The idea that energy metabolism is regulated by energy charge (as proposed by Atkinson, 1968, 1977) is misleading in mammals. Neither mitochondrial ATP synthesis nor cellular ATP usage is a unique function of energy charge as AMP is not a significant regulator (see for example Erecinska et al., 1977). The near-equilibrium hypothesis of Klingenberg (1961) and Erecinska & Wilson (1982) is partially correct in that oxidative phosphorylation is often close to equilibrium (apart from cytochrome oxidase) and as a consequence respiration and ATP synthesis are mainly regulated by (a) the phosphorylation potential, and (b) the NADH/NAD+ ratio. However, oxidative phosphorylation is not always close to equilibrium, at least in isolated mitochondria, and relative proximity to equilibrium does not prevent the respiratory chain, the proton leak, the ATP synthase and ANC having significant control over the fluxes. Thus in some conditions respiration rate correlates better with [ADP] than with phosphorylation potential, and may be relatively insensitive to mitochondrial NADH/NAD+ ratio.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Control of respiration and ATP synthesis in mammalian mitochondria and cells. 159 89

The mRNA levels of ATPase beta, ATPase 6, cytochrome oxidase (COX) VIb and COX I subunits were found to be 2.4-13.8-fold higher in brown adipose tissue (BAT) than in heart, skeletal muscle, brain and liver of mice. The comparison with tissue contents of ATPase and COX revealed that the selective, 5-11-fold reduction of ATPase in BAT is not caused by decreased transcription of ATPase genes. Likewise, the ATPase beta and COX VIb mRNA levels in cultured brown adipocytes were also not influenced by norepinephrine, which activated the expression of the UCP gene by two orders of magnitude. The results indicate that the biosynthesis of mitochondrial ATPase in BAT is post-transcriptionally regulated.
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PMID:Low content of mitochondrial ATPase in brown adipose tissue is the result of post-transcriptional regulation. 166 83

Mitochondria are the main site of ATP synthesis in aerobic cells, using the free energy of the oxidation of metabolic fuels by oxygen. They have a matrix space containing the enzymes of the citrate cycle and beta-oxidation, enclosed by an inner membrane containing the 4 complexes of the electron transport chain, ATP synthase and specific carriers for metabolites. Mitochondria also have a relatively permeable outer membrane and an intermembrane space. ATP synthesis (oxidative phosphorylation) is critically dependent on the structural integrity of the mitochondrion. Electrons from substrate oxidations feed into the electron transport chain at complex I or complex II, and then successively flow to complex III, complex IV and finally to oxygen. Complexes I, III and IV are redox pumps and electron transport causes extrusion of protons from the matrix generating an electrochemical proton gradient (proton motive force) across the inner membrane. Protons return to the matrix 'through' ATP synthase driving the synthesis of ATP. The stoichiometry of proton extrusion and the yield of ATP are still uncertain. Mitochondria have genetic continuity and are inherited maternally. They possess a small amount of DNA which codes for some, but not all, of the subunits of complexes I, III, IV of ATP synthase. mtDNA also codes for mitochondrial ribosomal and messenger RNAs involved in the synthesis of mitochondrially coded subunits. All other mitochondrial peptides are synthesised on cytosolic ribosomes and are imported and targeted to their specific intramitochondrial locations, often after proteolytic removal of leader sequences.
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PMID:Mitochondria: structure and function. 196 47


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