GENETICALLY STRUCTURED MATHEMATICAL-MODELING OF TRP ATTENUATOR MECHANISM

A genetically structured mathematical model of the trp attenuator in E scherichia coli based on known coupling mechanisms of the transcriptio n of the trp leader region and translation of the trp leader peptide r egion is proposed. The model simulates, both qualitatively and quantit atively, the effects of tryptophan on the repression of cloned gene pr oducts. It shows that repression by attenuation mechanism alone operat es over a narrow trp concentration range of 1 to 5 mu M compared with 1 to 100 mu M for trp repressor mechanism. This implies that attenuati on by transcription termination is not relaxed until tryptophan starva tion is severe. Simulation results show that the attenuator starts to derepress when the repressor is about 40% repressed, and becomes signi ficantly derepressed only when the repressor repression decreased to a bout 20%. Unlike the case of repressor-operator interaction, the opera ting range of tryptophan concentration in the attenuator mechanism is not sensitive to plasmid copy number. (C) 1998 John Wiley & Sons, Inc.