A kirromycin-resistant EF-Tu species reverses streptomycin dependence of Escherichia coli strains mutated in ribosomal protein S12.
Microbiology (Reading)
; 144 ( Pt 12): 3309-3316, 1998 Dec.
Article
em En
| MEDLINE
| ID: mdl-9884222
ABSTRACT
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-TuA(R) 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 (Sm1) 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 Sm1 strains when they include wt EF-Tu or EF-Tu[G222D].
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Proteínas Ribossômicas
/
Estreptomicina
/
Fator Tu de Elongação de Peptídeos
/
Escherichia coli
/
Antibacterianos
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Microbiology (Reading)
Assunto da revista:
MICROBIOLOGIA
Ano de publicação:
1998
Tipo de documento:
Article