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Repressible Operon: trp Operon

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Related Experiment Video

Updated: May 13, 2026

PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase

PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase

Published on: September 26, 2020

A metabolic prototype for eliminating tryptophan from the genetic code.

V Pezo¹, D Louis, V Guérineau

¹CEA, DSV, IG, Genoscope, 2 rue Gaston Crémieux, 91057 Evry Cedex, France. valerie.pezo@issb.genopole.fr

Scientific Reports

|March 1, 2013

Summary

This summary is machine-generated.

Scientists reduced the amino acid count in E. coli by reassigning the tryptophan codon to histidine. This genetic code evolution was stably maintained through metabolic selection over 2500 generations.

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Engineering 'Golden' Fluorescence by Selective Pressure Incorporation of Non-canonical Amino Acids and Protein Analysis by Mass Spectrometry and Fluorescence

Engineering 'Golden' Fluorescence by Selective Pressure Incorporation of Non-canonical Amino Acids and Protein Analysis by Mass Spectrometry and Fluorescence

Published on: April 27, 2018

Area of Science:

Synthetic Biology
Molecular Biology
Genetics

Background:

The standard genetic code utilizes 20 canonical amino acids.
Modifying the genetic code offers insights into its evolution and potential for novel biological functions.

Purpose of the Study:

To engineer a strain of Escherichia coli (E. coli) with a reduced amino acid repertoire, specifically eliminating tryptophan.
To investigate the stability and evolution of a reassigned genetic code under selective pressure.

Main Methods:

Constructed an E. coli strain where the tryptophan codon (UGG) was reassigned to histidine.
Replaced histidine codons in an essential enzyme gene with tryptophan codons and selected for functional restoration via a suppressor tRNA.
Utilized automated cultivation for long-term propagation and stability assessment over 2500 generations.

Main Results:

Successfully engineered an E. coli strain with a reassigned genetic code, replacing tryptophan with histidine.
Demonstrated stable propagation of the genetic construct over extended cultivation.
Observed a significant increase in histidine misincorporation at tryptophan sites in the proteome, indicating adaptation.

Conclusions:

The genetic code can be experimentally evolved and stabilized through permanent metabolic selection.
This work provides a foundation for engineering organisms with altered amino acid compositions and exploring the plasticity of the genetic code.