PMID:9367785
| Citation |
Qian, Q and Björk, GR (1997) Structural alterations far from the anticodon of the tRNAProGGG of Salmonella typhimurium induce +1 frameshifting at the peptidyl-site. J. Mol. Biol. 273:978-92 |
|---|---|
| Abstract |
A total of 12 Salmonella typhimurium mutants were selected with mutations in the minor tRNAProGGG which suppress a +1 frameshift mutation in the hisD gene. This tRNA normally has 1-methylguanosine (m1G37) next to and 3' of the anticodon (position 37). Since the presence of m1G37 prevents frameshifting, some of the +1 frameshift suppressor derivatives of tRNAProGGG had alterations in the primary sequence abolishing the formation of m1G37. However, several of the mutant tRNAProGGG species had a normal level of m1G37 and a normal-sized anticodon loop, showing that neither m1G37 deficiency, nor an oversized anticodon loop, is a prerequisite for +1 frameshifting. Moreover, base substitutions far from the anticodon, e.g. in the acceptor stem, DHU-loop and stem, and at the top of the anticodon stem, promoted +1 frameshifting. When the frameshifting site (CCC-Uaa; CCC is in the zero frame and a +1 frameshift moves the ribosome to the CC-U codon) is overlapped by a nonsense codon (UAA), the efficiency of frameshifting decreased when release factor 1 was over-expressed and increased at an elevated temperature in a mutant with a temperature-sensitive release factor 1. The frameshifting site (CCC-Uac) was also overlapped with the sense codon UAC, which is decoded by a tRNA species having a 2-methylthio-cis ribozeatin (ms2io6A) at position 37. Mutations in the miaA gene affect the formation of this modified nucleoside and result in an A instead of ms2io6A37 in the tRNA. Such an undermodified tRNA is very inefficient in translation and the efficiency of frameshifting increased in a miaA1 mutant. These results suggest that the frameshifting event occurs at the P-site, since the efficiency of frameshifting was sensitive to the decoding activity of the overlapping codon. We conclude that tRNA with mutations far from the anticodon, with a normal-sized anticodon loop and having m1G37 induce +1 frameshifting at the P-site. |
| Links | |
| Keywords |
Alcohol Oxidoreductases; Anticodon; Bacterial Proteins/genetics; Base Sequence; Chromosomes, Bacterial/genetics; DNA, Bacterial/chemistry; DNA, Bacterial/genetics; Frameshift Mutation; Gene Expression Regulation, Bacterial; Genes, Reporter; Genetic Code; Guanosine/analogs & derivatives; Guanosine/chemistry; Molecular Sequence Data; Mutagenesis, Insertional; Nucleic Acid Conformation; Peptide Chain Elongation, Translational; Plasmids/genetics; RNA, Bacterial/genetics; RNA, Transfer, Amino Acyl/genetics; RNA, Transfer, Pro/genetics; Recombinant Fusion Proteins/biosynthesis; Salmonella typhimurium/genetics; Temperature |
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