Pre-binding of small protein B to a stalled ribosome triggers trans-translation.
To rescue stalled ribosomes, eubacteria employ a molecule, transfer messenger RNA (tmRNA), which functions both as a tRNA and as an mRNA. With the help of small protein B (SmpB), tmRNA restarts protein synthesis and adds by the trans-translation mechanism a peptide tag to the stalled protein to target it for destruction by cellular proteases. Here, the cellular location and expression of endogenous SmpB were monitored in vivo. We report that SmpB is associated with 70S ribosomes and not in the soluble fraction, independently of the presence of tmRNA. In vitro, SmpB that is pre-bound to a stalled ribosome can trigger initiation of trans-translation. Our results demonstrate the existence of a novel pathway for the entry of tmRNA to the ribosome and for the trans-transfer of a nascent peptide chain from peptidyl-tRNA to charged tmRNA.
Hallier
Marc
M
Biochimie Pharmaceutique, Universite de Rennes I, Unite Propre a la Recherche et a l'Enseignement Superieur Jeune Equipe 2311, 2 avenue du Pr. Leon Bernard, 35043 Rennes, France.
Ivanova
Natalia
N
Rametti
Armelle
A
Pavlov
Michael
M
Ehrenberg
Måns
M
Felden
Brice
B
D015152:Blotting, Northern; D002455:Cell Division; D002499:Centrifugation, Density Gradient; D004926:Escherichia coli / Q000378:metabolism; D005816:Genetic Complementation Test; D015151:Immunoblotting; D009154:Mutation; D011485:Protein Binding; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000737:chemistry*; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D012270:Ribosomes / Q000737:chemistry* / Q000378:metabolism; D013347:Subcellular Fractions; D013395:Sucrose / Q000494:pharmacology; D013997:Time Factors
D012329:RNA, Bacterial; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C430328:small protein B; C096222:tmRNA; D013395:Sucrose