Modelling the evolution of the archeal tryptophan synthase

Area of Science:

• Microbiology
• Evolutionary Biology
• Biochemistry

Background:

• Tryptophan biosynthesis involves enzymes encoded by the trp operon, including trpA and trpB, which code for tryptophan synthase subunits.
• Two variants of the trpB gene (trpB1 and trpB2) exist in prokaryotic genomes, with their evolutionary history being a subject of ongoing research.

Purpose of the Study:

• To investigate the evolutionary history of trpB gene variants (trpB1 and trpB2) across archaeal and bacterial genomes.
• To characterize the different trpB variants and their relationship with tryptophan synthase A (TrpA) protein interactions and operon organization.

Main Methods:

• Phylogenetic analysis of trpB genes from completely sequenced archaeal and bacterial genomes.
• In silico characterization of trpB variants and TrpA/TrpB cooperation using phylogenetic trees, bootstrapping, and parsimony arguments.

Main Results:

• TrpB sequences formed four distinct phylogenetic groups, correlating with gene location (operon vs. non-operon) and species.
• Identified trpB2 as the likely ancestral form, with trpB1 evolving in an ancestral bacterium, and characterized different stages of TrpA/TrpB cooperation.
• Correlated trpB variant groups with archaeal speciation, revealing insights into operon formation.

Conclusions:

• Archeal genomes provide a valuable model system for studying the evolution of protein-protein interactions and operon formation.
• The study elucidates the evolutionary trajectory of trpB genes and the development of TrpA/TrpB functional cooperation.