title: Accurate genetic switch in Escherichia coli: novel mechanism of regulation by co-repressor.
abstract: Understanding a biological module involves recognition of its structure and the dynamics of its principal components. In this report we present an analysis of the dynamics of the repression module within the regulation of the trp operon in Escherichia coli. We combine biochemical data for reaction rate constants for the trp repressor binding to trp operator and in vivo data of a number of tryptophan repressors (TrpRs) that bind to the operator. The model of repression presented in this report greatly differs from previous mathematical models. One, two or three TrpRs can bind to the operator and repress the transcription. Moreover, reaction rates for detachment of TrpRs from the operator strongly depend on tryptophan (Trp) concentration, since Trp can also bind to the repressor-operator complex and stabilize it. From the mathematical modeling and analysis of reaction rates and equilibrium constants emerges a high-quality, accurate and effective module of trp repression. This genetic switch responds accurately to fast consumption of Trp from the interior of a cell. It switches with minimal dispersion when the concentration of Trp drops below a thousand molecules per cell.
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland. marcin@leon.ichf.edu.pl
authors.forename: Marcin
authors.initials: M
authors.lastname: Tabaka
authors.forename: Olgierd
authors.initials: O
authors.lastname: Cybulski
authors.forename: Robert
authors.initials: R
authors.lastname: Hołyst
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008969:Molecular Sequence Data; D009876:Operon / Q000187:drug effects; D009994:Osmolar Concentration; D012097:Repressor Proteins / Q000502:physiology*; D014364:Tryptophan / Q000378:metabolism / Q000494:pharmacology; D029968:Escherichia coli Proteins
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D014364:Tryptophan; C027190:TRPR protein, E coli; D029968:Escherichia coli Proteins