PMID:9600836
| Citation |
Seabold, RR and Schleif, RF (1998) Apo-AraC actively seeks to loop. J. Mol. Biol. 278:529-38 |
|---|---|
| Abstract |
In the absence of arabinose and interactions with other proteins, AraC, the activator-repressor that regulates the araBAD operon in Escherichia coli, was found to prefer participating in DNA looping interactions between the two well-separated DNA half-sites, araI1 and araO2 at their normal separation of 211 base-pairs rather than binding to these same two half-sites when they are adjacent to one another. On the addition of arabinose, AraC preferred to bind to the adjacently located half-sites. Inverting the distally located araO2 half-site eliminated the looping preference. These results demonstrate that apo-AraC possesses an intrinsic looping preference that is eliminated by the presence of arabinose. We developed a method for the accurate determination of the relative affinities of AraC for the DNA half-sites araI1, araI2, and araO2 and non-specific DNA. These affinities allowed accurate calculation of basal level and induced levels of expression from pBAD under a wide variety of natural and mutant conditions. The calculations independently predicted the looping preference of apo-AraC. |
| Links |
PubMed Online version:10.1006/jmbi.1998.1713 |
| Keywords |
Apoproteins/biosynthesis; Apoproteins/metabolism; AraC Transcription Factor; Arabinose/genetics; Bacterial Proteins; Base Sequence; DNA, Bacterial/chemistry; DNA, Bacterial/metabolism; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins; Gene Expression Regulation, Bacterial; Kinetics; Mathematics; Models, Genetic; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Nucleic Acid Conformation; Oligodeoxyribonucleotides; Operon; Recombinant Fusion Proteins/biosynthesis; Regulatory Sequences, Nucleic Acid; Repressor Proteins/biosynthesis; Repressor Proteins/metabolism; Transcription Factors; beta-Galactosidase/biosynthesis |
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