Peter Dimroth

..Three possible inter-subunit ion-bridges are likely to account for the remarkable temperature stability of I.tartaricus c-rings compared to those of other organisms...

..Conversely, the carboxyl transferase domain of KpOadA exhibited catalytic activity not only with its pertinent biotin domain but also withAfOadC...

..This peptide therefore represents a newly identified, separate domain of the alpha-subunit and has been called the 'association domain'...

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..Reconstituted TA2F(o)F(1)(epsilon(6A)) exhibited ATPase activity that correlated with increased ATP-driven proton pumping, confirming that the epsilon subunit also inhibits ATPase activity of TA2F(o)F(1)...

..Here, we incorporate recent results on structure and function of the F(0) domain and present a mechanism for torque generation with the fundamental nature of the membrane potential as driving force in the core...

..These conclusions are corroborated by the finding that only the membrane potential induces a rotary torque that drives the counter-rotation of the a and c subunits in the F(o) motor of Propionigenium modestum ATP synthase...

..This new type of energy conservation has been termed decarboxylation phosphorylation and is responsible entirely for ATP synthesis in several anaerobic bacteria...

..With H(+) entering from the periplasm, the hydroxyl group of S382 is regenerated, and as a consequence, the Na(+) ions are released into this compartment. After switching back to the original conformation, Na(+) pumping continues...

..In the second part, we provide a detailed description of the F(1)F(0) ATP synthases with special emphasis on the Na(+)-translocating variant of these enzymes...

..The genetic evidence firmly supports the idea that malonate decarboxylation is carried out by the two different decarboxylases, as deduced from the biochemical studies of the enzymes...

..Taken together with biophysical data, the operating principles of the motor have been delineated...

..This mechanism allows efficient interaction between subunit a and the c-ring and simultaneously allows almost frictionless movement against each other...

..Single-molecule studies with dual-labeled CitS-sC398-AF(546/568) and dual-color detection provided strong evidence for a homodimeric association of CitS...

..The concept of two different binding sites in the ATP synthase family is supported by the ATP hydrolysis pH profiles of the investigated enzymes...

..The new method is an ideal tool for detailed kinetic investigations of the ion transport mechanism of ATP synthases from various organisms...

..A similar bending of the gamma shaft as in the TA2F(1) structure was observed by single-particle analysis of the TA2F(1)F(o) holoenzyme...

..5 were required for ATP synthesis in vitro. This discrepancy is discussed with respect to the hypothesis that during respiration lateral proton diffusion could lead to significant acidification at the membrane surface...

..OAD is a membrane-bound enzyme composed of alpha, beta and gamma subunits. The alpha subunit contains the carboxyltransferase catalytic site...

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..We conclude therefore that the inner lumen of the c ring is occupied with phospholipids. No evidence was found for an extension of subunit a into this space...

..No NADH-driven proton transport into the lumen of proteoliposomes was detected. We conclude that Na(+) is used as the exclusive coupling ion by the enterobacterial complex I...

..The common membrane embedded location of the binding site of ATP synthases suggest a common mechanism for ion transfer across the membrane...

..Our results are congruent with a stable c11 ring stoichiometry that seems to not be influenced by the expression level of subunit c in the bacteria...

..Taken together these results indicate that the subunit a ion channel is the target site for ATPase inhibition by toxic organotin compounds. An inhibitor interacting specifically with this site has not been reported previously...

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..The positions of the binding sites for CitB and of putative recognition sequences for the cAMP receptor protein suggested a model for the interaction of these activators with RNA polymerase...

..Moreover, upon the incubation with the F0-specific inhibitor dicyclohexylcarbodiimide the rotation was severely inhibited...

..The substitutions were found exclusively at the fatty acid side chains, which indicates that c-Glu(65) is located within the core of the membrane...

..6 units mg(-1), 2.4 units mg(-1), and 4.7 units mg(-1), respectively, which indicate a Na(+)/electron stoichiometry of one...

..The two oad gene clusters were heterologously expressed in Escherichia coli, and the decarboxylases were isolated from the host cells...

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..These data indicate that catabolite repression of the citrate fermentation genes is exerted by CRP and that in the absence of repressing carbon sources the cAMP-CRP complex serves to enhance the basal, CitB-dependent transcription level...

..It is suggested that the E. coli CitT protein is a member of a novel family of eubacterial transporters involved in the transport of di- and tricarboxylic acids...

..A.24). The substrate specificity seems to partially contradict this phylogenetic classification, but appears logical with respect to the putative functional role of CitW in the citrate fermentation pathway of K. pneumoniae...

..As partial deletion of the mdcR gene impaired growth of the transformants on malonate, MdcR is probably a transcriptional regulator of the mdc genes...

..A plasmid encoding the three oad genes and that for the anaerobic citrate carrier (citS) was cloned from the chromosomal DNA and used for sequence determination...

..In the presence of these signals, the citAB gene products induced their own synthesis. The positive autoregulation occurred via co-transcription of citAB with citS and oadGAB...

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..modestum in the organic solvent also deviated from that of Escherichia coli in the same environment, the most important difference being that subunit c of P. modestum did not adopt a stable hairpin structure like subunit c of E. coli...

..platensis showed 15 symmetrically assembled subunits. The c15-mer reported here is the largest c ring that is isolated and does not show the classical c-ring mismatch to the three-fold symmetry of the F1 domain...

..These and other data strongly indicated that the enzyme synthesized in E. coli lacked its prosthetic group. Thus, additional genes besides citCDEFG appear to be required for the formation of holo-citrate lyase...

..Second, holo-ACP is formed from apo-ACP and the prosthetic group precursor in a reaction catalyzed by CitX...

..We propose a catalytic mechanism for torque generation by the F(o) motor that is in accord with all experimental data and is in quantitative agreement with the requirement for ATP synthesis...

..A model of Na+ translocation by oxaloacetate decarboxylase based on these experimental results is proposed...

..With an E. coli mutant deficient in complex I, the Na+ transport activity was low (1-3 nmol mg-1 min-1), and rotenone was without effect...

..The increase in fluorescence intensity correlated with the loss of enzyme activity. Gel filtration of the Ag+-treated Na+-NQR confirmed that FAD had been displaced from the holo-enzyme...

..alginolyticus. It is shown that the [2Fe-2S] cluster previously assigned to the Na+-NQR originates from the succinate dehydrogenase or the related enzyme fumarate reductase...

..The phylogenetic relationship between the Na(+)-translocating ATPase of P. modestum and other F1F0 ATPases has been clearly demonstrated by sequencing studies...

..Furthermore, this precursor was transferred by CitX to apo-ACP, yielding holo-ACP. Thus, our proposed mechanism for holo-ACP synthesis could be verified...

..As the detergent-purified c cylinder is completely devoid of phospholipids, these are incorporated into the central hole from one side of the cylinder during the reconstitution procedure...

..A1 correlated well with the DeltapNa(+), phosphorylation potential, and the ATP/ADP ratio, but not with Deltap. This communication represents the first report on the bioenergetics of an extremely thermoalkaliphilic aerobic bacterium...

..The operation of a c ring with 13 subunits renders the thermodynamic problem of ATP synthesis at alkaline pH less severe and may represent a strategy for ATP synthesis at low electrochemical potential...

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..On the basis of these results, it was determined that the F-ATPase from C. paradoxum contains an undecameric c ring...

..modestum and c(11) from Ilyobacter tartaricus. These Fo hybrids had Na(+) translocation activities that were not distinguishable from that of P. modestum F(o)...

..The betaR389C mutant had a reduced activity and a pH optimum at pH 9, which could be restored to a wild-type pH optimum of 6.5 and to a 400% gain in activity upon chemical modification with 2-aminoethyl methanethiosulfonate...

..This work also illustrates how to extract a motor mechanism from dynamical experimental observations in the absence of complete structural information...

..For ATP synthesis the rate constant is 50-70 s(-1)...

..During the countertransport of 2 Na+ and 1 H+ Y229 of center II switches between the protonated and deprotonated Na+-bound state...

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..Site-directed mutagenesis strengthens the essential role of glutamate 65 in the crossbridging of the subunits and also corroborates the proposed stabilizing effect of an ion bridge including aspartate 2...

..A1 membranes. ATPase assays of F(1)Deltadelta crystals exhibited latent ATP hydrolytic activity that was highly stimulated by lauryldimethylamine oxide, a hallmark of the native enzyme...

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..These results indicate that aspartate 62, histidine 77, and histidine 82 of the gamma subunit are ligands for the catalytically important Zn(2+) metal ion...

..A1, as documented previously for mesophilic alkaliphilic Bacillus species. The ATP synthase was specifically modified at its c subunits by N,N'-dicyclohexylcarbodiimide, and this modification inhibited ATP synthesis...

..Furthermore, the two new examples of c(15) rings underline once more that an F(1)/F(o) symmetry mismatch is not an obligatory feature of all F-ATP synthases...

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