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)

Individual subunits of ATP synthase, encoded by the eight genes of the atp operon (atpA through atpH), have been found to be synthesized at a 10-fold range in molar amounts (D.L. Foster and R.H. Fillingame, J. Biol. Chem. 257:2009-2015, 1982; K. von Meyenburg, B.B. Jorgensen, J. Nielsen, F.G. Hansen, and O. Michelsen. Tokai J. Exp. Clin. Med. 7:23-31, 1982). We have determined the functional half-lives at 30 degrees C of mRNAs transcribed from these genes either during constitutive expression in a partial diploid strain or after induced expression from a plasmid. Accurate decay kinetics of the relative mRNA levels were determined by monitoring the rates of synthesis of the individual ATP synthase subunits by radioactive pulse labeling at different times after blocking transcription initiation with rifampin. The mRNA transcribed from the atp operon was found to be inactivated about twice as fast as the bulk mRNA in E. coli. Exceptions are the mRNA from the promoter-proximal atpB gene, which was inactivated about three times as fast as the bulk mRNA, and atpC mRNA, the inactivation rate of which was comparable to that of the bulk mRNA. These moderate differences in the kinetics of functional decay explain only a minor part of the differences in expression levels of the atp genes. We conclude, therefore, that the individual atp mRNAs must be translated with widely different efficiencies. The present analysis further revealed that mRNA degradation is sensitive to heat shock; i.e., after incubation at 39 degrees C for 5 min followed by a shift back to 30 degrees C, the decay rate of the bulk mRNA was decreased by 30%.
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PMID:Limited differential mRNA inactivation in the atp (unc) operon of Escherichia coli. 769 Jul 47

Theories of biological energy coupling in oxidative phosphorylation (OX PHOS) and photophosphorylation (PHOTO PHOS) are reviewed and applied to ATP synthesis by an experimental system containing purified ATP synthase reconstituted into liposomes. The theories are critically evaluated from the standpoint of the principle of electrical neutrality. It is shown that the obligatory requirement to maintain overall electroneutrality of bulk aqueous phases imposes strong constraints on possible theories of energy coupling and molecular mechanisms of ATP synthesis. Mitchell's chemiosmotic theory is found to violate the electroneutrality of bulk aqueous phases and is shown to be untenable on these grounds. Purely electroneutral mechanisms or mechanisms where the anion/countercation gradient is dissipated or simply flows through the lipid bilayer are also shown to be inadequate. A dynamically electrogenic but overall electroneutral mode of ion transport postulated by Nath's torsional mechanism of energy transduction and ATP synthesis is shown to be consistent both with the experimental findings and the principle of electrical neutrality. It is concluded that the ATP synthase functions as a proton-dicarboxylic acid anion cotransporter in OX PHOS or PHOTO PHOS. A logical chemical explanation for the selection of dicarboxylic acids as intermediates in OX PHOS and PHOTO PHOS is suggested based on the pioneering classical thermodynamic work of Christensen, Izatt, and Hansen. The nonequilibrium thermodynamic consequences for theories in which the protons originate from water vis-a-vis weak organic acids are compared and contrasted, and several new mechanistic and thermodynamic insights into biological energy transduction by ATP synthase are offered. These considerations make the new theory of energy coupling more complete, and lead to a deeper understanding of the molecular mechanism of ATP synthesis.
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PMID:Analysis of molecular mechanisms of ATP synthesis from the standpoint of the principle of electrical neutrality. 2831 6