title: Flavodoxin mutants of Escherichia coli K-12.
abstract: The flavodoxins are flavin mononucleotide-containing electron transferases. Flavodoxin I has been presumed to be the only flavodoxin of Escherichia coli, and its gene, fldA, is known to belong to the soxRS (superoxide response) oxidative stress regulon. An insertion mutation of fldA was constructed and was lethal under both aerobic and anaerobic conditions; only cells that also had an intact (fldA(+)) allele could carry it. A second flavodoxin, flavodoxin II, was postulated, based on the sequence of its gene, fldB. Unlike the fldA mutant, an fldB insertion mutant is a viable prototroph in the presence or absence of oxygen. A high-copy-number fldB(+) plasmid did not complement the fldA mutation. Therefore, there must be a vital function for which FldB cannot substitute for flavodoxin I. An fldB-lacZ fusion was not induced by H(2)O(2) and is therefore not a member of the oxyR regulon. However, it displayed a soxS-dependent induction by paraquat (methyl viologen), and the fldB gene is preceded by two overlapping regions that resemble known soxS binding sites. The fldB insertion mutant did not have an increased sensitivity to the effects of paraquat on either cellular viability or the expression of a soxS-lacZ fusion. Therefore, fldB is a new member of the soxRS (superoxide response) regulon, a group of genes that is induced primarily by univalent oxidants and redox cycling compounds. However, the reactions in which flavodoxin II participates and its role during oxidative stress are unknown.
authors.affiliation: Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: P
authors.initials: P
authors.lastname: Gaudu
authors.forename: B
authors.initials: B
authors.lastname: Weiss
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D001483:Base Sequence; D001665:Binding Sites; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D005418:Flavodoxin / Q000235:genetics* / Q000378:metabolism; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005798:Genes, Bacterial / Q000235:genetics* / Q000502:physiology; D020043:Genes, Essential / Q000235:genetics / Q000502:physiology; D005816:Genetic Complementation Test; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D018384:Oxidative Stress / Q000235:genetics; D010100:Oxygen / Q000378:metabolism; D010269:Paraquat / Q000494:pharmacology; D010641:Phenotype; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018085:Regulon / Q000235:genetics; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D005418:Flavodoxin; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C070724:SoxR protein, Bacteria; C070725:SoxS protein, E coli; D006861:Hydrogen Peroxide; D010269:Paraquat; D010100:Oxygen