| 1. |
- Ban, Nenad, et al.
(författare)
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A new system for naming ribosomal proteins.
- 2014
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Ingår i: Current Opinion in Structural Biology. - : Elsevier BV. - 1879-033X .- 0959-440X. ; 24, s. 165-169
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Tidskriftsartikel (refereegranskat)abstract
- A system for naming ribosomal proteins is described that the authors intend to use in the future. They urge others to adopt it. The objective is to eliminate the confusion caused by the assignment of identical names to ribosomal proteins from different species that are unrelated in structure and function. In the system proposed here, homologous ribosomal proteins are assigned the same name, regardless of species. It is designed so that new names are similar enough to old names to be easily recognized, but are written in a format that unambiguously identifies them as 'new system' names.
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| 2. |
- Ivanova, Natalia, 1974-
(författare)
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Finding the unknowns in trans-translation
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ribosomes stalled on problematic mRNAs can be rescued by a mechanism called trans-translation. This mechanism employs a dual transfer-messenger RNA molecule (tmRNA) together with a helper protein (SmpB). In this work we have used an in vitro translation system with pure components to further clarify the roles of tmRNA and SmpB in trans-translation. We found that SmpB binds ribosomes in vivo and in vitro independently of tmRNA presence and is essential for tmRNA binding and trans-peptidation. We show that two SmpB molecules can bind per ribosome, that SmpB does not leave the ribosome after trans-peptidation and that SmpB pre-bound to the ribosome can trigger trans-translation. We demonstrated that the rate of trans-transfer of a peptide from the P-site tRNA to Ala-tmRNA and the efficiency by which Ala-tmRNA competes with peptide release factors decrease with increasing the mRNA length downstream from the P site of the ribosome. We showed that trans-translation is strongly stimulated by RelE cleavage of A-site mRNA. We concluded that tmRNA action in vivo must always be preceded by mRNA truncation.We showed that rapid release of truncated mRNAs from the ribosome requires translocation of the peptidyl-tmRNA into the ribosomal P site, which is strictly EF-G dependent. mRNA release is slowed down by strong Shine and Dalgarno like sequences upstream the A site and by long 3’-extensions downstream from the P-site codon. Footprinting was used to monitor SmpB binding to tmRNA, ribosomes and subunits and to study tmRNA interactions with the ribosome at distinct trans-translation stages. We confirmed that two SmpB molecules bind per ribosome and interact with nucleotides below the L7/L12-stalk on the 50S subunit and near the subunit interface on the 30S. We showed that tmRNA is mostly in complex with SmpB in vivo and during trans-translation. Specific cleavage patterns of tmRNA were observed at different stages of trans-translation, but the overall tmRNA conformation seems to be maintained during the whole process.
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