Protein:protein interactions in control of a transcriptional switch.
Article Details
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Adikaram PR, Beckett D
Protein:protein interactions in control of a transcriptional switch.
J Mol Biol. 2013 Nov 15;425(22):4584-94. doi: 10.1016/j.jmb.2013.07.029. Epub 2013 Jul 26.
- PubMed ID
- 23896299 [ View in PubMed]
- Abstract
Protein partner exchange plays a key role in regulating many biological switches. Although widespread, the mechanisms dictating protein partner identity and, therefore, the outcome of a switch have been determined for a limited number of systems. The Escherichia coli protein BirA undergoes a switch between posttranslational biotin attachment and transcription repression in response to cellular biotin demand. Moreover, the functional switch reflects formation of alternative mutually exclusive protein:protein interactions by BirA. Previous studies provided a set of alanine-substituted BirA variants with altered kinetic and equilibrium parameters of forming these interactions. In this work, DNase I footprinting measurements were employed to investigate the consequences of these altered properties for the outcome of the BirA functional switch. The results support a mechanism in which BirA availability for DNA binding and, therefore, transcription repression is controlled by the rate of the competing protein:protein interaction. However, occupancy of the transcriptional regulatory site on DNA by BirA is exquisitely tuned by the equilibrium constant governing its homodimerization.