%0 Journal Article %A Zuurmond, Anne-Marie %A Zeef, Leo A. H. %A Kraal, Barend %T A kirromycin-resistant EF-Tu species reverses streptomycin dependence of Escherichia coli strains mutated in ribosomal protein S12 %D 1998 %J Microbiology, %V 144 %N 12 %P 3309-3316 %@ 1465-2080 %R https://doi.org/10.1099/00221287-144-12-3309 %K rpsL, translational accuracy %K elongation factor Tu %K error-prone mutations %I Microbiology Society, %X Summary: Streptomycin dependence can be caused by mutations in ribosomal protein S12. Mutations suppressing such streptomycin dependence have been found in ribosomal proteins S4 and S5, and in 16S rRNA. Here a new suppressor mutation localized in elongation factor Tu (EF-Tu) is described, consistent with recent models of ribosome-EF-Tu-tRNA interaction at the decoding centre. The EF-Tu mutation was obtained by genetic selection for streptomycin independence; it was identified as Ala375 → Thr, previously described as EF-TuAR and known to confer a kirromycin-resistant, error-prone phenotype. Also, other streptomycin-dependent (SmD) S12 mutations could be complemented by this mutation. The streptomycin-independent (SmI) strain grows more slowly than the wild-type (wt), suggesting that not all the defects of the S12 mutation can be complemented by EF-Tu[A375T]. Moreover, this strain is more susceptible than wt to reduction in the cellular EF-Tu concentration, and disruption of tufB led to considerable growth-rate impairment. Expression of EF-Tu from tufB, not only of wt EF-Tu and EF-Tu[A375T] but, remarkably, also of EF-Tu[G222D], known as EF-TuB0 and defective in protein synthesis, equally contributed to cell growth. In vitro analysis revealed a decreased translational activity of wt EF-Tu with SmD ribosomes as compared to EF-Tu[A375T], while EF-Tu[G222D] showed no activity at all, just as with wt ribosomes. Possible mechanisms are discussed for the improved growth rate observed in such SmI strains when they include wt EF-Tu or EF-Tu[G222D]. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-144-12-3309