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Two distinct classes of FixJ binding sites defined by in vitro selection
Lionel Ferrières1, Daniel Kahn
1Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, UMR 215 INRA-CNRS, Chemin de Borde-Rouge, P.O. Box 27, Castanet-Tolosan, France.
FEBS Letters
|June 14, 2002
Summary
Researchers identified two distinct DNA binding modes for the FixJ protein, a key activator of nitrogen fixation in Sinorhizobium meliloti. This finding clarifies how FixJ regulates essential genes for this process.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Nitrogen fixation is crucial for plant growth and is regulated by specific transcriptional activators.
- The FixJ protein in Sinorhizobium meliloti is a key activator of nitrogen fixation genes, including nifA and fixK.
- Previous studies lacked a clear understanding of the consensus sequences targeted by FixJ.
Purpose of the Study:
- To systematically characterize the DNA binding sequences of the FixJ transcriptional activator.
- To elucidate the distinct binding modes employed by FixJ on DNA.
Main Methods:
- In vitro DNA selection techniques were employed to identify and characterize FixJ binding sequences.
- Sequence analysis was performed to define consensus binding sites.
Main Results:
- Two distinct classes of FixJ binding sites were identified.
- Class I sites share similarity with the sequence in the fixK promoter (CTAAGTAGTTTCCC).
- Class II sites are characterized by a GTAMGTAG consensus octamer.
Conclusions:
- FixJ approximately P binds to DNA through at least two distinct binding modes.
- These findings provide a clearer understanding of the molecular mechanisms regulating nitrogen fixation gene expression in Sinorhizobium meliloti.