Evolutionary Changes in Isoleucyl-tRNA Synthetase Accelerate Bacterial Protein Production
Evolutionary changes in the key protein synthesis enzyme isoleucyl-tRNA synthetase help bacteria fine-tune how quickly proteins are made, according to a study published on October 12, 2026, in the journal Nature Communications. Researchers from Institute of Science Tokyo, the University of Zagreb Faculty of Science, and ETH Zürich traced the enzyme’s evolutionary history to identify three distinct clades.
C-Terminal Remodeling and INS Subdomain Loss in Prokaryotes
The research team found that C-terminal remodeling, including the repeated loss of an approximately 80-amino-acid structural region called the INS subdomain across multiple prokaryotic lineages, helped refine enzyme activity and reaction speed. Professor Liam M. Longo from the Earth-Life Science Institute at Institute of Science Tokyo noted that bacteria have repeatedly streamlined parts of this enzyme, which potentially enhances the aminoacylation rate and contributes to faster protein synthesis.
To investigate the functional significance of the INS subdomain, the research team determined the crystal structure of IleRS2 from Priestia megaterium bound to a tRNA from Escherichia coli. This marked the first reported crystal structure of an IleRS containing the evolutionarily unstable INS subdomain. Laboratory experiments revealed that while the INS subdomain contributes to tRNA binding, it is not essential for productive aminoacyl transfer under the conditions assayed.
Mutational Effects and Catalytic Turnover in Escherichia Coli
Mutations that weakened the interaction between the INS subdomain and the tRNA D-loop increased the enzyme’s catalytic turnover by about fourfold. Eliminating the INS subdomain entirely lowered the enzyme’s apparent affinity toward tRNA, elevating the KM for tRNA by about 15-fold while maintaining aminoacylation function. According to Professor Ita Gruic-Sovulj of the Department of Chemistry at the University of Zagreb Faculty of Science, evolutionary alterations within the C-terminal area can modify IleRS-tRNA binding dynamics without necessarily impairing its core catalytic activity.
When tested inside Escherichia coli, modified enzymes carrying mutations in the INS subdomain successfully supported bacterial growth even when the bacteria’s own IleRS was blocked. Complete removal of the INS domain made complementation more difficult, but the mutant enzyme remained functional when expressed at higher levels alongside additional tRNA for isoleucine. In contrast, mutations disrupting the tRNA anticodon recognition site completely prevented the enzyme from supporting bacterial growth.
Frequently Asked Questions About IleRS Evolution
What journal published the IleRS evolutionary study?
The study was published in the journal Nature Communications on October 12, 2026.
How many distinct IleRS clades did the researchers identify?
The international research team identified three distinct IleRS clades while tracing the enzyme’s evolutionary history through bioinformatics, X-ray crystallography, and kinetic characterization.
What happened to the bacterial enzyme when the INS subdomain was completely removed?
When the entire INS subdomain was deleted, the enzyme’s apparent tRNA affinity dropped, causing roughly a 15-fold rise in the KM for tRNA, yet aminoacylation capability persisted.
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