TRNA2Gln Su+2 mutants that increase amber suppression

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Amber mutations are nonsense mutations that cause premature termination of translation.
• Transfer RNA (tRNA) molecules play a crucial role in protein synthesis by carrying amino acids to the ribosome.
• Suppressor tRNA mutations can overcome the effects of nonsense mutations, allowing for the production of full-length proteins.

Purpose of the Study:

• To identify and characterize mutations in lambda pSu+2 that enhance its ability to suppress amber mutations.
• To investigate the structural and functional consequences of these mutations on tRNA2Gin Su+2.

Main Methods:

• Selection of lambda pSu+2 mutants with increased amber mutation suppression in E. coli.
• Purification and sequencing of tRNA2Gin Su+2 molecules from mutant isolates.
• Mapping of mutations to the tRNA2Gin Su+2 (glnV) gene.
• Analysis of suppressor activity and amino acid insertion at amber sites.

Main Results:

• Eight independent mutants with enhanced amber suppression were identified.
• Two types of mutations were mapped to the tRNA2Gin Su+2 gene, both affecting pseudouridine at position 37.
• Seven mutations were transitions (pseudouridine to cytosine), and one was a transversion (pseudouridine to adenine).
• Mutant Su+ tRNA molecules showed higher transmission coefficients and inserted glutamine at amber sites, similar to the parent Su+2.

Conclusions:

• Mutations at position 37 of tRNA2Gin Su+2 can enhance its suppressor activity.
• These alterations in tRNA structure lead to improved translation efficiency and suppression of amber mutations.
• The findings provide insights into tRNA structure-function relationships and suppressor tRNA mechanisms.