Biochemistry 2280A Lecture : Trp Operon
Document Summary
In e. coli the 5 genes for tryptophan biosynthesis are transcribed from a common promoter. In ecoli, 5 genes required for trypophan biosynthesis (genes requried to make tryptophan) is expressed on same rna and translated form that common rna. The operon shown edcba they make diff rpotein products which are required for tryp biosynthesis. The key here: these genes are required for synthesis. Cell wants to turn them on when it needs tryptophan when it can t get it from env. This occurs when there is very little tryptophan around. It would rather use tryptophan from env if it could. If it can t, it has to make its own tryptophan by turning on the gene. Between the -35 and -10 sequences is an element called the trp operator that binds a protein called the trp repressor. When tryptophan is low, tryptophan dissociates from the trp repressor. The trp repressor no longer binds the trp operator.