title: Occurrence of ferredoxin:NAD(+) oxidoreductase activity and its ion specificity in several Gram-positive and Gram-negative bacteria.
abstract: A ferredoxin:NAD(+) oxidoreductase was recently discovered as a redox-driven ion pump in the anaerobic, acetogenic bacterium Acetobacterium woodii. The enzyme is assumed to be encoded by the rnf genes. Since these genes are present in the genomes of many bacteria, we tested for ferredoxin:NAD(+) oxidoreductase activity in cytoplasmic membranes from several different Gram-positive and Gram-negative bacteria that have annotated rnf genes. We found this activity in Clostridium tetanomorphum, Clostridium ljungdahlii, Bacteroides fragilis, and Vibrio cholerae but not in Escherichia coli and Rhodobacter capsulatus. As in A. woodii, the activity was Na(+)-dependent in C. tetanomorphum and B. fragilis but Na(+)-independent in C. ljungdahlii and V. cholerae. We deleted the rnf genes from B. fragilis and demonstrated that the mutant has greatly reduced ferredoxin:NAD(+) oxidoreductase activity. This is the first genetic proof that the rnf genes indeed encode the reduced ferredoxin:NAD(+) oxidoreductase activity.
authors.affiliation: Molecular Microbiology and Bioenergetics, Goethe University Frankfurt , Frankfurt am Main , Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Hess
authors.affiliation: Department of Molecular Biology and Microbiology, Tufts University, School of Medicine and Sackler School of Graduate Biomedical Sciences , Boston, Masachusetts , United States.
authors.forename: Rene
authors.initials: R
authors.lastname: Gallegos
authors.affiliation: Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute , Troy, New York , United States.
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Jones
authors.affiliation: Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute , Troy, New York , United States.
authors.forename: Blanca
authors.initials: B
authors.lastname: Barquera
authors.affiliation: Department of Molecular Biology and Microbiology, Tufts University, School of Medicine and Sackler School of Graduate Biomedical Sciences , Boston, Masachusetts , United States.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Malamy
authors.affiliation: Molecular Microbiology and Bioenergetics, Goethe University Frankfurt , Frankfurt am Main , Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Müller
keywords: Energy conservation; Fdred:NAD+ oxidoreductase; Ion pump; Rnf