Correlating protein footprinting with mutational analysis in the bacterial transcription factor sigma54 (sigmaN)
| Autor: | Martin Buck, Siva R. Wigneshweraraj, Paul Casaz |
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| Rok vydání: | 2002 |
| Předmět: |
Transcription
Genetic HMG-box DNA Mutational Analysis Electrophoretic Mobility Shift Assay Sigma Factor Biology Nucleic Acid Denaturation Article chemistry.chemical_compound Bacterial Proteins Transcription (biology) RNA polymerase Coactivator Genetics Protein Footprinting Binding site Promoter Regions Genetic Binding Sites Base Sequence General transcription factor Escherichia coli Proteins Temperature Promoter DNA DNA-Directed RNA Polymerases DNA-binding domain beta-Galactosidase Protein Structure Tertiary DNA-Binding Proteins Amino Acid Substitution Biochemistry chemistry Trans-Activators Nucleic Acid Conformation Holoenzymes RNA Polymerase Sigma 54 |
| Zdroj: | Nucleic Acids Research. 30:1016-1028 |
| ISSN: | 1362-4962 |
| DOI: | 10.1093/nar/30.4.1016 |
| Popis: | Protein footprints of the enhancer-dependent sigma54 protein, upon binding the Escherichia coli RNA polymerase core enzyme or upon forming closed promoter complexes, identified surface-exposed residues in sigma54 of potential functional importance at the interface between sigma54 and core RNA polymerases (RNAP) or DNA. We have now characterised alanine and glycine substitution mutants at several of these positions. Properties of the mutant sigma54s correlate protein footprints to activity. Some mutants show elevated DNA binding suggesting that promoter binding by holoenzyme may be limited to enable normal functioning. One such mutant (F318A) within the DNA binding domain of sigma54 shows a changed interaction with the promoter regulatory region implicated in transcription silencing and fails to silence transcription in vitro. It appears specifically defective in preferentially binding to a repressive DNA structure believed to restrict RNA polymerase isomerisation and is largely intact for activator responsiveness. Two mutants, one in the regulatory region I and the other within core interacting sequences of sigma54, failed to stably bind the activator in the presence of ADP-aluminium fluoride, an analogue of ATP in the transition state for hydrolysis. Overall, the data presented describe a collection sigma54 mutants that have escaped previous analysis and display an array of properties which allows the role of surface-exposed residues in the regulation of open complex formation and promoter DNA binding to be better understood. Their properties support the view that the interface between sigma54 and core RNAP is functionally specialised. |
| Databáze: | OpenAIRE |
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