trp Operon,Tryptophan,Anabolic Enzymes,Repressor,Structural Gene

	trp Operon - The trp operon consists of the genes for the enzymes that are needed to make the amino acid tryptophan. The trp operon on the other hand codes for anabolic enzymes that build up a substance. Such operons are generally turned off by that substance. when the tryptophan concentration is high, the product of the trp operon is not needed any longer and so the trp operon also exhibits an extra level of control not seen in the lac operon.
1. Repressor: The trp repressor binds to the operator site. The core binding site is a palindrome of 18 bp. The trp repressor binds to tryptophan if present in the medium. Repressor can only bind to the operator when it is complexed with tryptophan. The repressor is a dimer of two subunits, which have structural affinity towards the operator site 2. Structural gene : The trp operon structural gene consists of 5 genes ( trpE, trpP, trpc, trpB and trpA). The operon encodes a single transcription unit which is 7 kb in length.