Step 3: Since the inactive repressor protein is unable to bind to the Operator region, RNA polymerase (the enzyme responsible for the transcription of genes) is able to bind to the Promoter region of the trp operon.
Step 4: RNA polymerase is now able to transcribe the five trp operon structural genes (trpE, trpD, trpC, trpB, and trpA) into mRNA.
Step 5: With the transcription of these genes, the five enzymes needed for the bacterium to synthesize the amino acid tryptophan are now made.

TrpE and TrpD are the two subunits for making anthranilate synthetase, the enzyme that catalyzes the first two reactions in the tryptophan pathway.
TrpC is is indole glycerolphosphate synthetase, the enzyme that catalyzes the next two steps in the pathway.
TrpB and TrpA are subunits for making tryptophan synthetase. the enzyme that catalizes the synthesis of tryptophan from indole-glycerol phosphate and serine.

Illustration of A Repressible Operon in the Absence of a Corepressor (The Tryptophan Operon).jpg by Gary E. Kaiser, Ph.D.
Professor of Microbiology, The Community College of Baltimore County, Catonsville Campus
This work is licensed under a Creative Commons Attribution 4.0 International License.
Based on a work at https://cwoer.ccbcmd.edu/science/microbiology/index_gos.html.

Last updated: August, 2018
Please send comments and inquiries to Dr. Gary Kaiser