Chemiosmotic energy conservation with Na(+) as the coupling ion during hydrogen-dependent caffeate reduction by Acetobacterium woodii.
Cell suspensions of Acetobacterium woodii prepared from cultures grown on fructose plus caffeate catalyzed caffeate reduction with electrons derived from molecular hydrogen. Hydrogen-dependent caffeate reduction was strictly Na(+) dependent with a K(m) for Na(+) of 0.38 mM; Li(+) could substitute for Na(+). The sodium ionophore ETH2120, but not protonophores, stimulated hydrogen-dependent caffeate reduction by 280%, indicating that caffeate reduction is coupled to the buildup of a membrane potential generated by primary Na(+) extrusion. Caffeate reduction was coupled to the synthesis of ATP, and again, ATP synthesis coupled to hydrogen-dependent caffeate reduction was strictly Na(+) dependent and abolished by ETH2120, but not by protonophores, indicating the involvement of a transmembrane Na(+) gradient in ATP synthesis. The ATPase inhibitor N,N'-dicyclohexylcarbodiimide (DCCD) abolished ATP synthesis, and at the same time, hydrogen-dependent caffeate reduction was inhibited. This inhibition could be relieved by ETH2120. These experiments are fully compatible with a chemiosmotic mechanism of ATP synthesis with Na(+) as the coupling ion during hydrogen-dependent caffeate reduction by A. woodii.
Imkamp
Frank
F
Lehrstuhl für Mikrobiologie der Ludwig-Maximilians-Universität München, D-80638 Munich, Germany.
Müller
Volker
V
D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D002109:Caffeic Acids / Q000378:metabolism*; D019069:Cell Respiration; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004734:Energy Metabolism; D005051:Eubacterium / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D010084:Oxidation-Reduction; D012964:Sodium / Q000378:metabolism*
D002109:Caffeic Acids; D004024:Dicyclohexylcarbodiimide; D006859:Hydrogen; D000255:Adenosine Triphosphate; D012964:Sodium; C040048:caffeic acid