High concentrations of ppGpp decrease the RNA chain growth rate. Implications for protein synthesis and translational fidelity during amino acid starvation in Escherichia coli.
J Mol Biol
; 236(2): 441-54, 1994 Feb 18.
Article
em En
| MEDLINE
| ID: mdl-7508988
ABSTRACT
We show that the RNA chain growth rate on lacZ is reduced by an elevated ppGpp level even in the absence of starvation. Under these conditions the polypeptide chain elongation rate is affected little, if at all. These results lead us to re-examine the role of ppGpp in the reduction of protein synthesis and translational fidelity during amino acid starvation. We find that ppGpp has little or no direct effect on translation rate or fidelity. Rather, the effects of ppGpp on translation are indirectly caused by the fact that ppGpp inhibits mRNA synthesis, making mRNA limiting for translation during amino acid starvation. The reduced level of mRNA thereby reduces the severity of the aminoacyl-tRNA limitation and, in turn, decreases mistranslation. Mistranslation in the starved relA strain therefore results from an increased severity of aminoacyl-tRNA limitation due to the failure of this strain to reduce mRNA levels by increasing the level of ppGpp. Finally, the initial rise of the ppGpp level in the starved stringent strain, followed by a characteristic reduction to a steady poststarved level, can now be explained by the initially high, and then decreasing number of "hungry" codons adjusted through the mRNA pool.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
/
Biossíntese de Proteínas
/
RNA Mensageiro
/
Escherichia coli
/
Guanosina Tetrafosfato
Idioma:
En
Revista:
J Mol Biol
Ano de publicação:
1994
Tipo de documento:
Article
País de afiliação:
Dinamarca