Studies of energy‐linked reactions: A lipoic acid requirement for oxidative phosphorylation in Escherichia coli

Oxidative phosphorylation and proton translocation in a lipoate‐deficient mutant ofEscherichia coli

“…coli free of any detectable amount of free or bound lipoate. These findings are in contrast with [1][2][3][4][5][6]. In addition the observation of a DBCT-sensitive ATPase activity in these membranes casts some doubts on the proposal that DBCT inhibition is only due to a specific and covalent interaction with membrane-associated lipoic acid.…”

“…According to [1,4] the terminal reactions of phosphorylation in membranous systems involve a cycle of transacylation and transphosphorylation reactions analogous to those involved in substrate level phosphorylation. The main evidence in support of this proposal is the observation that membrane vesicles from the lipoic acid-auxotroph mutant Escherichia coli W1485 lip2 are not able to carry out electron flow-dependent ATP synthesis and that incubation for a short time of these preparations with lipoic acid restores this capability fully [3].…”

“…On the basis of experiments performed in a large variety of energy-transducing systems and on isolated ATPase complex from mitochondria, a fundamental role in the mechanism of membrane-associated ATP synthesis is played by lipoic acid has been suggested, which should provide the link coupling the electrontransport chains and the ATP-synthetase complexes [1][2][3]. According to [1,4] the terminal reactions of phosphorylation in membranous systems involve a cycle of transacylation and transphosphorylation reactions analogous to those involved in substrate level phosphorylation.…”

Studies of energy‐linked reactions: Oleoyl phosphate‐dependent ATP synthesis (oleoyl phosphokinase) activity of membrane ATPase and soluble ATPases from mitochondria, chloroplasts, chromatophores and Escherichia coli plasma membrane

“…The specific cofactor requirement for a cis unsaturated fatty acid [4,19] is also demonstrable at the acyl phosphate level as the frans isomer, elaidoyl phosphate and the saturated fatty acid derivative, palmitoyl phosphate, are inactive as substrates and are inhibitors of the olebyl phosphokinase reaction (table 2). The sensitivity of the reaction to DCCD and the Fr-ATPase inhibitor, efrapeptin, characterises the reaction as a representative partial reaction of the oxidative phosphorylation sequence.…”

“…Chloroplasts were isolated from pea seedlings (Pisum sativum) as described by Blair and Ellis [ 141. Escherichia coli was grown and membrane vesicles prepared as described [4] . Membrane vesicles were prepared from cells washed twice in 0.25 M sucrose, 10 mM MgCl,, 50 mM Tris-Cl, pH 8.0, and resuspended in the same buffer.…”