Efficient separation of Thermus aquaticus EF-Tu functional complexes

Bacterial elongation factors EF-Tu, their mutants, chimeric forms, and domains: isolation and purification

Prokaryotic elongation factors EF-Tu form a family of homologous, three-domain molecular switches catalyzing the binding of aminoacyl-tRNAs to ribosomes during the process of mRNA translation. They are GTP-binding proteins, or GTPases. Binding of GTP or GDP regulates their conformation and thus their activity. Because of their particular structure and regulation, various activities (also outside of the translation system) and a relative abundance they represent attractive tools for studies of many basic but still not fully understood mechanisms both of the translation process, the structure-function relationships in EF-Tu molecules themselves and proteins and energy transduction mechanisms in general. The review critically summarizes procedures for the isolation and purification of native and engineered eubacterial elongation factors EF-Tu and their mutants on a large as well as small scale. Current protocols for the purification of both native and polyHis-tagged or glutathione-S-transferase (GST)-tagged EF-Tu proteins and their variants using conventional procedures and the Ni-NTA-Agarose or Glutathione Sepharose are presented.

tmRNA from Thermus thermophilus. Interaction with alanyl-tRNA synthetase and elongation factor Tu

The interaction of a Thermus thermophilus tmRNA transcript with alanyl-tRNA synthetase and elongation factor Tu has been studied. The synthetic tmRNA was found to be stable up to 70 degrees C. The thermal optimum of tmRNA alanylation was determined to be around 50 degrees C. At 50 degrees C, tmRNA transcript was aminoacylated by alanyl-tRNA synthetase with 5.9 times lower efficiency (kcat/Km) than tRNAAla, primarily because of the difference in turnover numbers (kcat). Studies on EF-Tu protection of Ala approximately tmRNA against alkaline hydrolysis revealed the existence of at least two different binding sites for EF-Tu on charged tmRNA. The possible nature of these binding sites is discussed.