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The trp operon is a group of genes that are transcribed together, encoding the enzymes that produce the amino acid tryptophan in bacteria. The trp operon was first characterized in Escherichia coli , and it has since been discovered in many other bacteria. [ 1 ]
The trp operon consists of a regulatory gene, a promoter, an operator, and a terminator. The trp operon is active only when cellular tryptophan is scarce. If there isn't enough tryptophan, the repressor protein breaks off from the operator (where the repressor is normally bound) and RNA polymerase can complete its reading of the strand of DNA ...
Enzyme induction is a process in which a molecule (e.g., a drug) induces (i.e., initiates or enhances) the expression of an enzyme. The induction of heat shock proteins in the fruit fly Drosophila melanogaster. The Lac operon is an interesting example of how gene expression can be regulated.
Examples include the histidine (his) [18] [19] and tryptophan (trp) [20] biosynthetic operons. The term "attenuation" was introduced to describe the his operon. [ 18 ] While it is typically used to describe biosynthesis operons of amino acids and other metabolites, programmed transcription termination that does not occur at the end of a gene ...
For example, the E. coli tryptophan repressor (TrpR) is only able to bind to DNA and repress transcription of the trp operon when its corepressor tryptophan is bound to it. TrpR in the absence of tryptophan is known as an aporepressor and is inactive in repressing gene transcription. [2]
RNA polymerase can then begin to transcribe operon genes. By binding to activators. Activators generally bind poorly to activator DNA sequences unless an inducer is present. Activator binds to an inducer and the complex binds to the activation sequence and activates target gene. [2] Removing the inducer stops transcription. [2]
An inducible gene is a gene whose expression is either responsive to environmental change or dependent on the position in the cell cycle. Any step of gene expression may be modulated, from the DNA-RNA transcription step to post-translational modification of a protein. The stability of the final gene product, whether it is RNA or protein, also ...
This process is called promoter escape, and is another step at which regulatory elements can act to accelerate or slow the transcription process. Similarly, protein and nucleic acid factors can associate with the elongation complex and modulate the rate at which the polymerase moves along the DNA template.