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Interaction of high-affinity nucleotide binding sites in mitochondrial ATP synthesis and hydrolysis (1982)

Schäfer, G. ; Weber, J.

Springer

Journal of bioenergetics and biomembranes 14 (1982), S. 479-498

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ISSN: 1573-6881

Keywords: Oxidative phosphorylation ; F1-ATPase ; nucleotide binding sites ; cooperativity ; nucleotide analogs ; fluorescence ; mechanism

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Physics

Notes: Abstract The present study contributes to the problem of the dynamic structure of mitochondrial F1-ATPase and the functional interrelation of so-called tight nucleotide binding sites. Nucleotide analogs are used as a tool to differentiate two distinct functional states of the membrane-bound enzyme, proposed to reflect corresponding conformational states; they reveal F1-ATPase as a “dual-state” enzyme: ATP-synthetase, and ATP-hydrolase. The analogs used are 3′-naphthoyl esters of AD(T)P, and 2′(3′)-O-trinitrophenyl ethers of AD(T)P. Both types of analogs act inversely to each other with respect to their relative effects on oxidative phosphorylation and on ATPase in submitochondrial vesicles. The respective ratios ofK i versus both processes are 250/1 compared to 1/170. It is also shown that in the presence of the inhibitory 3′-esters oxidative phosphorylation deviates from linear kinetics and that these inhibitors induce a lag time of oxidative phosphorylation depending on the initial pattern of nucleotides available to energized submitochondrial vesicles. The duration of the lag time coincides with the time course of displacement of the analog from a tight binding site. The conclusions of the study are: (a) the catalytic sites of F1-ATP-synthetase are not operating independently from each other; they rather interact in a cooperative manner; (b) F1-ATPase as a “dual-state” enzyme exhibits highly selective responses to tight binding of nucleotides or analogs in its “energized” (membrane-bound) state versus its “nonenergized” state, respectively.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00743073

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Cytokine production and DNA synthesis by Human peripheral Lymphocytes in response to Palmitic, Stearic, Oleic, and Linoleic acid (1994)

Karsten, S. ; Schäfer, G. ; Schauder, P.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 161 (1994), S. 15-22

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ISSN: 0021-9541

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: Effects of palmitic, stearic, oleic, and linoleic acid on mitogen-induced DNA synthesis, on production of IL-1β, IL-2, IFN-gamma, and TNF-α, and on IL-2R expression were determined in human peripheral lymphocytes. Free fatty acids (FFA) were added over a wide range of concentrations to cells cultured under serum free conditions with fatty acid free albumin. DNA synthesis was stimulated by low and inhibited by high FFA concentrations. Physiologica concentrations were stimulatory, except for linoleic acid. Cytokine production became affected by all FFA tested. Palmitic acid enhanced the release of IFN-gamma at concentrations that diminished TNF-α production. Saturated fatty acids were significantly more potent than unsaturated fatty acids in affecting cytokine production. IFN-gamma secretion was significantly more stimulated or inhibited by the various FFA compared with the other cytokines. IL-2R expression correlated with the production of IL-2. When tested in combination, stimulatory as well as inhibitory effects of the individual FFA became attenuated. It is suggested that palmitic, stearic, oleic, and linoleic acid are physiological regulators of DNA synthesis and cytokine release in human peripheral lymphocytes. Modulation of FFA ratios may be an effective means for the fine tuning of the immune system. As secretory mechanisms of cytokines appear to exhibit substrate specificity for FFA, the release of individual cytokines may be selectively influenced by FFA. © 1994 Wiley-Liss, Inc.

Additional Material: 4 Ill.