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OmpR mutants specifically defective for transcriptional activation
1Department of Molecular Biology, Princeton University, NJ 08544.
Journal of Molecular Biology
|November 4, 1994
Summary
Researchers identified five key amino acid residues in the OmpR protein essential for activating gene transcription in Escherichia coli. These findings shed light on the OmpR-EnvZ regulatory system controlling outer membrane porin expression.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The OmpR-EnvZ two-component system regulates outer membrane porin (OmpF, OmpC) expression in Escherichia coli.
- OmpR acts as a transcriptional regulator, activating ompC and both activating/repressing ompF.
- OmpR-mediated activation is proposed to involve interaction with the RNA polymerase alpha subunit's C-terminal domain, but the specific OmpR region is unknown.
Purpose of the Study:
- To identify specific amino acid residues in OmpR critical for transcriptional activation.
- To elucidate the region of OmpR involved in interacting with RNA polymerase for transcriptional activation.
Main Methods:
- Screening for ompR mutations defective in transcriptional activation.
- Characterizing isolated ompR alleles via haploid/diploid analyses at ompF and ompC promoters.
- Utilizing in vivo DNA binding assays.
Main Results:
- Five amino acid residues (R42, P179, E193, A196, E198) were identified as specifically required for OmpR's transcriptional activation function.
- These residues likely define a region of OmpR involved in contacting the RNA polymerase alpha subunit.
Conclusions:
- The identified residues are crucial for OmpR-mediated transcriptional activation.
- This study proposes a specific region within OmpR that interacts with the RNA polymerase alpha subunit's C-terminal domain to facilitate transcription initiation.