Tryptophan In Eukaryotic Synthesis

Prokaryotes, specifically bacteria, have feedback regulatory mechanisms like eukaryotes do to make tryptophan. Tryptophan is one of the 20 amino acids which we all need. If there is a lot of tryptophan made, then you turn off the enzymes that are involved in tryptophan synthesis by binding and causing a change in shape of the enzyme (negative feedback). In addition, repressors are proteins that bind to the operator and prevents expression of the gene. However, the repressor is unable to bind to the operator unless tryptophan is present, in which case the tryptophan is a corepressor which is a small molecule that binds to the repressor. When there is a lot of tryptophan, it will bind to the repressor causing a change in shape of the repressor which allows it to bind to the operator. …show more content…
Overtime, the concentration of tryptophan decreases because the cell will use it to make other proteins and this means it will no longer bind to the repressor. This causes the repressor to detach from the operator which essentially will turn the genes back on again because the RNA polymerase isn’t blocked anymore. Therefore, without tryptophan, a bacteria cannot make any other proteins. All together, the operator, promoter, and the genes they control (entire stretch of DNA required for tryptophan production) is called the operon or trp operon. Prokaryotes can make one big mRNA that will be translated into multiple proteins at once, whereas eukaryotes make an mRNA per gene. A repressible operon is when transcription of an operon, like trp operon, is usually on but can be turned off when a small molecule binds to a regulatory protein. On the other hand, an inducible operon is when the transcription is usually off, but can be turned on when a certain molecule binds to a regulatory protein. A good example would be lactose. When lactose is present, then the genes need to be turned on in order to digest