SmpB functions in various steps of trans-translation
AUTOR(ES)
Hanawa-Suetsugu, Kyoko
FONTE
Oxford University Press
RESUMO
tmRNA has a dual function as a tRNA and an mRNA to facilitate trans-translation, in which a ribosome can switch between translation of a truncated mRNA and the tmRNA’s tag sequence. SmpB is a tmRNA binding protein that has been identified to be essential for trans-translation in vivo. To further study the function of SmpB, an S30 fraction from an Escherichia coli strain, in which the set of genes for SmpB and tmRNA has been deleted from the genome, and His-tagged SmpB active in trans-translation were prepared. The SmpB-depleted S30 fraction had an ability to facilitate poly(U)-dependent tag-peptide synthesis in vitro when purified His-tagged SmpB was exogenously added together with tmRNA, although SmpB was not required for in vitro poly(U)-dependent poly(Phe) synthesis. It was also found that depletion of SmpB leads to a decrease in the level of tmRNA in the cell. In addition, SmpB considerably enhanced the aminoacylation of tmRNA by alanyl-tRNA synthetase in vitro. The aminoacylation enhancement by SmpB, the binding of SmpB to tmRNA and the effect of depletion of SmpB on the expression level of tmRNA in the cell were all affected by some mutations in the tRNA-like domain which cause a defect in ribosome binding leading to a trans-translation deficiency. These results demonstrate that, via binding to the tRNA-like domain of tmRNA, SmpB plays various roles: rescuing the tmRNA molecule from degradation in the cell, enhancing the aminoacylation of tmRNA and mediating the binding of tmRNA to ribosome.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=101834Documentos Relacionados
- A previously uncharacterized role for small protein B (SmpB) in transfer messenger RNA-mediated trans-translation
- A minimum structure of aminoglycosides that causes an initiation shift of trans-translation
- Analysis of the Role of trans-Translation in the Requirement of tmRNA for λimmP22 Growth in Escherichia coli
- An NMR and mutational analysis of an RNA pseudoknot of Escherichia coli tmRNA involved in trans-translation.
- Gonadal and extragonadal expression of inhibin alpha, beta A, and beta B subunits in various tissues predicts diverse functions.