Attenuator riboswitch (Leader sequence) region 1 is translated  till UGA (R1-2) at high trp concentration due to two conditions

1. Ribosome quickly crosses codon 10, 11

2. After crossing codon 10, 11 ribosome prematurely terminated at UGA at the end of Region 1

TLS Online TPP Program

#Id: 6412

#Unit 2. Cellular Organization

In case of Low trp concentration, RNA polymerase continues to EDCBA genes where new ribosome get attached to AUG of polycistronic genes

TLS Online TPP Program

#Id: 6413

#Unit 2. Cellular Organization

on attenuation for their control. In the case of the leucine operon, its leader peptide has four adjacent leucine codons, and the histidine operon leader peptide has seven histidine codons in a row.

TLS Online TPP Program

#Id: 6414

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 6415

#Unit 2. Cellular Organization

RNA Polymerase don’t get dissociated with one hairpin which is 2:3

TLS Online TPP Program

#Id: 6416

#Unit 2. Cellular Organization

Transcription is initiated at the beginning of the 162 nucleotide mRNA leader encoded by a DNA region called trpL

TLS Online TPP Program

#Id: 6417

#Unit 2. Cellular Organization

The trp operon is controlled by repression and attenuation, providing a two-stage response to progressively more stringent tryptophan starvation. But attenuation alone can provide robust regulation: other amino acid operons such as leu and his rely entirely on attenuation for their control. In the case of the leucine operon, its leader peptide has four adjacent leucine codons, and the histidine operon leader peptide has seven histidine codons in a row.