Modular structure of FixJ: homology of the transcriptional activator domain with the -35 binding domain of sigma factors.
The FixL/FixJ two-component system is a global regulator of nitrogen-fixation genes in Rhizobium meliloti. The transcriptional activator FixJ contains two modules: its N-terminal module is homologous with other two-component regulators; its C-terminal module shows homology with various transcriptional activators, and with the C-terminal region of sigma factors, which is involved in the discrimination of the -35 region of bacterial promoters. We show that the C-terminal module of FixJ contains the entire transcription activation function, and that the N-terminal module regulates this activity negatively. Oligonucleotide-directed mutagenesis of the transcriptional activator module demonstrated the importance of a potential helix-turn-helix structure.
Kahn
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Center for Molecular Genetics, UCSD, La Jolla 92093.
Ditta
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D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004252:DNA Mutational Analysis; D005798:Genes, Bacterial; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000235:genetics*; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D012231:Rhizobium / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D012808:Sigma Factor / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D046911:Macromolecular Substances; D012097:Repressor Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C069289:FixJ protein, Bacteria