Structure-function analysis of tRNA(Gln) in an Escherichia coli knockout strain

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• RNA-protein interactions are crucial for biological processes, with glutamine aminoacylation serving as a model system.
• Crystal structures provide molecular insights into tRNA-protein interactions, guiding further investigation.

Purpose of the Study:

• To delineate key interactions governing structure-function relationships in RNA-protein systems.
• To identify specific mutations in transfer RNA (tRNA) that restore function in the glutamine aminoacylation system.

Main Methods:

• Disruption of chromosomal tRNA(Gln) genes in Escherichia coli to create a knockout strain.
• Hydroxylamine mutagenesis of an inactive tester tRNA (derived from tRNA(Ala)) followed by selection of active derivatives.
• Genetic selections, biochemical analyses, and utilization of existing crystal structure data.

Main Results:

• Two tRNA mutants with substitutions in the acceptor stem facilitated hairpin loop formation, positioning A76 in the active site.
• A third mutant, with a substitution in the D loop (position 13), suggested a role in conformational changes of glutamyl-tRNA synthetase (GlnRS).
• These mutations restored the ability of the tRNA to support the growth of the knockout strain.

Conclusions:

• An integrated approach combining genetic, biochemical, and structural data is effective for studying RNA-protein interactions.
• Specific tRNA modifications can significantly impact enzyme active site configuration and catalytic efficiency.
• The study elucidates molecular steps controlling specificity in RNA-protein interactions within the glutamine aminoacylation system.