Two-piece tmRNA in cyanobacteria and its structural analysis |
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Authors: | Gaudin Cyril Zhou Xiong Williams Kelly P Felden Brice |
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Institution: | Laboratoire de Biochimie Pharmaceutique, Faculté de Pharmacie, Université de Rennes I, UPRES Jeune Equipe 2311, IFR 97, 2 avenue du Pr Léon Bernard, 35043 Rennes cedex, France. |
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Abstract: | tmRNA acts to rescue stalled bacterial ribosomes while encoding a peptide tag added trans-translationally to the nascent peptide, targeting it for proteolysis. The permuted gene structure found in a group of cyanobacteria is shown to produce a two-piece mature tmRNA, as had been observed previously for the independently permuted gene of α-proteobacteria. The pieces have been mapped onto the gene sequence and aligned for the permuted cyanobacterial tmRNA sequences, including four novel sequences. Structural probing and base pair co-variations support a secondary structure model in which two pairings in the tRNA-like domain hold the two pieces together, and the coding piece bearing the tag reading frame additionally contains a single transient pseudoknot and three other stem–loops. This represents a dramatic reduction in pseudoknot number from the five present in one-piece cyanobacterial tmRNA. |
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