Turnover number of Escherichia coli F0F1 ATP synthase for ATP synthesis in membrane vesicles.

The rate of ATP synthesized by the ATP synthase (F0F1-ATPase) is limited by the rate of energy production via the respiratory chain, when measured in everted membrane vesicles of an Escherichia coli atp wild-type strain. After energization of the membranes with NADH, fractional inactivation of F0F1 by the covalent inhibitor N,N'-dicyclohexylcarbodiimide allowed the rate of ATP synthesis/mol remaining active ATP synthase complexes to increase; the active ATP synthase complexes were calculated using ATP hydrolysis rates as the defining parameter. In addition, variation of the assay temperature revealed an increase of the ATP synthesis rate up to a temperature of 37 degrees C, the optimal growth temperature of E. coli. In parallel, the amount of F0F1 complexes present in membrane vesicles was determined by immunoquantitation to be 3.3 +/- 0.3% of the membrane protein for cells grown in rich medium and 6.6 +/- 0.3% for cells grown in minimal medium with glycerol as sole carbon and energy source. Based on these data, a turnover number for ATP synthesis of 270 +/- 40 s(-1) could be determined in the presence of 5% active F0F1 complexes. Therefore, these studies demonstrate that the ATP synthase complex of E. coli has, with respect to maximum rates, the same capacity as the corresponding enzymes of eukaryotic organells.

ATP synthesis catalyzed by the ATP synthase of Escherichia coli reconstituted into liposomes.

The H(+)-translocating F0F1-ATPase from Escherichia coli (EF0F1) was purified and reconstituted into preformed reverse-phase liposomes prepared from egg yolk phosphatidylcholine/phosphatidic acid. The EF0F1 liposomes were energized by an acid/base transition (pHout = 8.3; pHin = 5.0) and a superimposed K+/valinomycin diffusion potential ([K+]out = 100 mM; [K+]in = 0.6 mM) yielding a maximum rate (turnover number) of ATP synthesis of 27 +/- 8 mol ATP . mol EF0F1(-1) . s-1), i.e. 27 +/- 8 s-1. This reaction was inhibited by NH4Cl or by addition of the F0F1 inhibitor N,N'-dicyclohexylcarbodiimide. The rate of ATP synthesis measured as a function of the phosphate and ADP concentrations, can be described by Michaelis-Menten kinetics with a Km of 0.7 +/- 0.2 mM for phosphate ([ADP] = 200 microM) and a Km of 27 +/- 7 microM for ADP ([phosphate] = 5 mM), respectively.

[Comparative clinical studies on 2 toothbrushing methods--Roll and Bass technic]. / Vergleichende klinische Untersuchungen zweier Zahnputz-methoden--Roll- und Bass-Technik.

The effectiveness of two tooth cleaning methods (Roll and Bass technique) was evaluated in 28 patients. Answers to the following questions were sought: 1. Which of the two methods results in greater reduction of plaque formation? 2. Are difficulties encountered in the learning and practice of each method? 3. Which method gives better results in the less accessible parts of the jaws? A significant difference in the cleaning effectiveness of the two methods could not be demonstrated.