title: Mutants of Escherichia coli specifically deficient in respiratory formate dehydrogenase activity.
abstract: Escherichia coli K12 mutants lacking phenazine-methosulphate-linked formate dehydrogenase (FDH-PMS) activity, but still capable of producing normal levels of benzyl-viologen-linked formate dehydrogenase (FDH-BV) and nitrate reductase activities, have been isolated following P1 localized mutagenesis. The relevant mutations mapped with the same cotransduction frequency close to the rhaD gene, at 88 min on the E. coli chromosome. They were further subdivided into two classes. Class I consisted of six fdhD mutants which synthesized an inactive FDH-PMS protein with the same subunit composition as the wild-type enzyme. In contrast, class II contained four fdhE mutants totally devoid of this antigen. Construction of merodiploid strains harbouring various combinations of the mutated alleles, fdhE on the episome and fdhD on the chromosome, led to the restoration of FDH-PMS activity by complementation of the products encoded by the respective wild-type alleles. Difference spectroscopy suggested that both fdhD and fdhE mutants contained normal amounts of the cytochrome b559 associated with FDH-PMS although the cytochrome had lost its capacity for formate-dependent reduction.
authors.affiliation: Laboratoire de Microbiologie, UM380024 du CNRS, Institut National des Sciences Appliquées de Lyon, Villeurbanne, France.
authors.forename: M A
authors.initials: MA
authors.lastname: Mandrand-Berthelot
authors.forename: G
authors.initials: G
authors.lastname: Couchoux-Luthaud
authors.forename: C L
authors.initials: CL
authors.lastname: Santini
authors.forename: G
authors.initials: G
authors.lastname: Giordano
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000172:deficiency*; D002874:Chromosome Mapping; D003573:Cytochrome b Group; D004926:Escherichia coli / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D005560:Formate Dehydrogenases / Q000172:deficiency*; D008773:Methylphenazonium Methosulfate / Q000378:metabolism*; D009154:Mutation; D010619:Phenazines / Q000378:metabolism*; D013054:Spectrophotometry, Atomic
chemical_list: D003573:Cytochrome b Group; D010619:Phenazines; D008773:Methylphenazonium Methosulfate; D005560:Formate Dehydrogenases; D000445:Aldehyde Oxidoreductases