Infrared Spectroscopy Labreport

The E.coli tryptophan operon includes five genes required to convert chorismate to tryptophan. Figure 1 When tryptophan is abundant it binds to the Tryptophan repressor, causing a conformational change that permits the repressor to bind to the tryptophan operator and inhibiting the expression of the tryptophan operon. An operon is a group of genes that is under the control of a single operator site. A regulatory protein called a repressor can bind to the operator site and prevent transcription. The tryptophan operator site overlaps the promoter, so binding of the repressor blocks the binding of RNA polymerase thus preventing transcription.

In the following research paper the Tryptophan repressor protein will be under scrutiny as key functions of the protein along with the interrelationships between structure and function will be examined. Furthermore intra and intermolecular interactions between residues along with key subunits will also be reviewed.

The Tryptophan repressor (or trp repressor) is a transcription factor involved in controlling amino acid metabolism. It has been best studied in Escherichia coli, where it is shown as a dimeric protein that regulates transcription of the five genes in the tryptophan operon. The Trp Repressor is allosterically regulated by the amino acid tryptophan. When tryptophan is present in high amounts in the cell it binds to the repressor which causes a conformational change in the protein activating it in a form of feedback regulation which will be discussed in greater detail.

Trp protein subunits

Trp repressor Dimer

Trp protein dimer with/without tryptophan

Functional Group interaction

Figure 2 This graphic represents the structure of trp-repressor bound to DNA as determined from NMR data obtained by Oleg Jardetzky and colleagues at Stanford Magnetic Resonance Laboratory. Structurally, trp-repressor is a symmetric dimer, a molecule formed of two identical subunits (light blue and pink) intertwined with each...