Dissection of the Caffeate Respiratory Chain in the Acetogen Acetobacterium woodii : Identification of an Rnf-Type NADH Dehydrogenase as a Potential Coupling Site

• DOI: 10.1128/jb.01017-07
• Publication Date: 2007-09-15T00:59:03Z
• Authors: Frank Imkamp; Eva Biegel; Elamparithi Jayamani; Wolfgang Buckel; Volker Müller
• Keywords: Chemiosmosis; NADH dehydrogenase; Hydrogenase

ABSTRACT The anaerobic acetogenic bacterium Acetobacterium woodii couples caffeate reduction with electrons derived from hydrogen to the synthesis of ATP by a chemiosmotic mechanism sodium ions as coupling ions, process referred respiration. We addressed nature hitherto unknown enzymatic activities involved in this and their cellular localization. Cell extract A. catalyzes H 2 -dependent reduction. This reaction is strictly dependent but can be activated also acetyl coenzyme A (CoA), indicating that there formation caffeyl-CoA prior Two-dimensional gel electrophoresis revealed proteins present only caffeate-grown cells. Two were identified electrospray ionization-mass spectrometry/mass spectrometry, encoding genes cloned. These are very similar subunits α (EtfA) β (EtfB) electron transfer flavoproteins various bacteria. Western blot analysis demonstrated they induced localized cytoplasm. Etf known carriers shuttle NADH different acceptors. Indeed, was used an donor for cytosolic Since hydrogenase soluble ferredoxin acceptor, missing link ferredoxin:NAD + oxidoreductase. activity could determined and, interestingly, membrane bound. search encode DNA fragments C D membrane-bound Rnf-type dehydrogenase potential Na pump. data suggest following transport chain: → NAD reductase. They imply motive step chain ferredoxin-dependent catalyzed Rnf.