title: Characterization of FNR* mutant proteins indicates two distinct mechanisms for altering oxygen regulation of the Escherichia coli transcription factor FNR.
abstract: In order to gain insight into the mechanism by which the Escherichia coli transcription factor FNR* is activated in response to anaerobiosis, we have analyzed FNR mutant proteins which, unlike the wild-type protein, stimulate gene expression in the presence of oxygen in vivo. Cell extracts containing seven different FNR* mutant proteins were tested in vitro for the ability to bind to the FNR consensus DNA site in a gel retardation assay under aerobic conditions. At the concentration of protein tested, only extracts which contained FNR* mutant proteins with amino acid substitutions at position 154 showed significant DNA binding. The three position-154 FNR* mutant proteins could be further distinguished from the other mutant proteins by analysis of the in vivo phenotypes of FNR* proteins containing amino acid substitutions at either of two essential cysteine residues. In the presence of oxygen, FNR* mutant proteins with amino acid substitutions at position 154 were the least affected when either Cys-23 or Cys-122 was substituted for Ser. On the basis of these in vivo and in vitro analyses, FNR* mutant proteins appear to segregate into at least two classes. Thus, it appears that each class of FNR* substitutions alters the normal pathway of FNR activation in response to oxygen deprivation by a different mechanism.
authors.affiliation: Department of Bacteriology, University of Wisconsin, Madison 53706, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Bates
authors.forename: B A
authors.initials: BA
authors.lastname: Lazazzera
authors.forename: P J
authors.initials: PJ
authors.lastname: Kiley
mesh_terms: D000332:Aerobiosis; D000595:Amino Acid Sequence; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D007506:Iron-Sulfur Proteins; D007763:Lac Operon / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010100:Oxygen / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012694:Serine / Q000235:genetics; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D007506:Iron-Sulfur Proteins; D012694:Serine; D003545:Cysteine; D010100:Oxygen