The Na(+) cycle in Acetobacterium woodii: identification and characterization of a Na(+) translocating F(1)F(0)-ATPase with a mixed oligomer of 8 and 16 kDa proteolipids.
The homoacetogenic bacterium Acetobacterium woodii relies on a sodium ion current across its cytoplasmic membrane for energy-dependent reactions. The sodium ion potential is established by a yet to be identified primary, electrogenic pump connected to the Wood-Ljungdahl pathway. Reactions possibly involved in Na(+) export are discussed. The electrochemical sodium ion potential generated is used to drive endergonic reactions such as flagellar rotation and ATP synthesis. Biochemical and molecular data identified the Na(+)-ATPase of A. woodii as a typical member of the F(1)F(0) class of ATPases. Its catalytic properties and the hypothetical sodium ion binding site in subunit c are discussed. The encoding genes were cloned and, surprisingly, the atp operon was shown to contain multiple copies of genes encoding subunit c. Two copies encode identical 8 kDa proteolipids, and a third copy arose by duplication and subsequent fusion of two genes. Furthermore, the duplicated subunit c does not contain the ion binding site in hair pin two. Biochemical and molecular data revealed that all three copies of subunit c constitute a mixed oligomer. The evolution of the structure and function of subunit c in ATPases from eucarya, bacteria, and archaea is discussed.
Lehrstuhl für Mikrobiologie der LMU München, Maria-Ward-Strasse 1a, 80638, Munich, Germany. v.mueller@lrz.uni-muenchen.de
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Aufurth
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D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D027682:Cation Transport Proteins; D002414:Cations, Monovalent; D004563:Electrochemistry; D019143:Evolution, Molecular; D016987:Gram-Positive Rods / Q000201:enzymology* / Q000235:genetics; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008956:Models, Chemical; D009876:Operon; D011510:Proteolipids / Q000737:chemistry / Q000235:genetics; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D002414:Cations, Monovalent; D011510:Proteolipids; D000255:Adenosine Triphosphate; D012964:Sodium; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase; D006180:Proton-Translocating ATPases