tailieunhanh - Báo cáo khoa học: Dynamic model of Escherichia coli tryptophan operon shows an optimal structural design

Amathematicalmodel hasbeendevelopedtostudy theeffect of external tryptophan on the trp operon. The model accounts for the effect of feedback repression by tryptophan through the Hill equation. We demonstrate that the trp operonmaintains an intracellular steady-state concentration in a fivefold range irrespective of extracellular conditions. Dynamic behavior of thetrp operon corresponding to varying levels of extracellular tryptophan illustrates the adaptive nature of regulation. | Eur. J. Biochem. 270 2644-2651 2003 FEBS 2003 doi Dynamic model of Escherichia coli tryptophan operon shows an optimal structural design Sharad Bhartiya1 Subodh Rawool1 and K. V. Venkatesh1 2 1 Department of Chemical Engineering and 2School of Biosciences and Bioengineering Indian Institute of Technology Bombay Mumbai India A mathematical model has been developed to study the effect of external tryptophan on the trp operon. The model accounts for the effect of feedback repression by tryptophan through the Hill equation. We demonstrate that the trp operon maintains an intracellular steady-state concentration in a fivefold range irrespective of extracellular conditions. Dynamic behavior of the trp operon corresponding to varying levels of extracellular tryptophan illustrates the adaptive nature of regulation. Depending on the external tryptophan level in the medium the transient response ranges from a rapid and underdamped to a sluggish and highly overdamped response. To test model fidelity simulation results are compared with experimental data available in the literature. We further demonstrate the significance of the biological structure of the operon on the overall performance. Our analysis suggests that the tryptophan operon has evolved to a truly optimal design. Keywords trp operon transcriptional control dynamic modeling tryptophan feedback repression. Cells use genetic switches to activate or repress expression of genes to a given stimuli. Many genetic switches have been discovered to date. Examples include lac operon 1 trp operon 2 k-phage switch 3 and gal switch 4 . The trp operon has been the subject of numerous studies both at the molecular level 5-11 and through mathematical models 12-21 . Experiments in molecular biology have demonstrated the basic biological structure of the operon. Although quantification and analysis of these switches have been attempted the specific effect of the genetic structure on the design of .

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