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Mol Microbiol. 1991 Apr;5(4):987-97.

Modular structure of FixJ: homology of the transcriptional activator domain with the -35 binding domain of sigma factors.

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Center for Molecular Genetics, UCSD, La Jolla 92093.


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.

[Indexed for MEDLINE]

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