The expression of nifB gene from Herbaspirillum seropedicae is dependent upon the NifA and RpoN proteins.
The putative nifB promoter region of Herbaspirillum seropedicae contained two sequences homologous to NifA-binding site and a -24/-12 type promoter. A nifB::lacZ fusion was assayed in the backgrounds of both Escherichia coli and H. seropedicae. In E. coli, the expression of nifB::lacZ occurred only in the presence of functional rpoN and Klebsiella pneumoniae nifA genes. In addition, the integration host factor (IHF) stimulated the expression of the nifB::lacZ fusion in this background. In H. seropedicae, nifB expression occurred only in the absence of ammonium and under low levels of oxygen, and it was shown to be strictly dependent on NifA. DNA band shift experiments showed that purified K. pneumoniae RpoN and E. coli IHF proteins were capable of binding to the nifB promoter region, and in vivo dimethylsulfate footprinting showed that NifA binds to both NifA-binding sites. These results strongly suggest that the expression of the nifB promoter of H. seropedicae is dependent on the NifA and RpoN proteins and that the IHF protein stimulates NifA activation of nifB promoter.
Rego
Fabiane G M
FG
Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Curitiba, PR, Brazil.
Pedrosa
Fábio O
FO
Chubatsu
Leda S
LS
Yates
M Geoffrey
MG
Wassem
Roseli
R
Steffens
Maria B R
MB
Rigo
Liu U
LU
Souza
Emanuel M
EM
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D042803:Herbaspirillum / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D034982:Integration Host Factors / Q000235:genetics / Q000378:metabolism; D007763:Lac Operon; D008969:Molecular Sequence Data; D010100:Oxygen / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D051877:RNA Polymerase Sigma 54 / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D034982:Integration Host Factors; C061338:NifA protein, Bacteria; C092498:NifB protein, Bacteria; D000644:Quaternary Ammonium Compounds; D014157:Transcription Factors; D051877:RNA Polymerase Sigma 54; D010100:Oxygen