| 1. |
- Faxén, Margareta, et al.
(författare)
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Is efficiency of suppressor tRNAs controlled at the level of ribosomal proofreading in vivo?
- 1988
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 170:8, s. 3756-3760
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Tidskriftsartikel (refereegranskat)abstract
- Ribosomal rpsD mutations did not stimulate nonsense suppressor tRNAs in a general manner according to their increased ribosomal ambiguity and decreased proofreading efficiency. Streptomycin, which stimulates error production by blocking proofreading in vitro, did not increase efficiency of suppressor tRNAs in strains with normal or streptomycin-resistant (rpsL) ribosomes. It did so only in combination with one rpsL mutation which is associated with streptomycin pseudodependence.
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| 2. |
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| 3. |
- Kirsebom, Leif A, et al.
(författare)
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Functional interactions in vivo between suppressor tRNA and mutationally altered ribosomal protein S4
- 1986
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Ingår i: Molecular General Genetics. - 0026-8925 .- 1432-1874. ; 205:2, s. 240-247
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Tidskriftsartikel (refereegranskat)abstract
- Ribosomal mutants (rpsD) which are associated with a generally increased translational ambiguity were investigated for their effects in vivo on individual tRNA species using suppressor tRNAs as models. It was found that nonsense suppression is either increased, unaffected or decreased depending on the codon context and the rpsD allele involved as well as the nature of the suppressor tRNA. Missense suppression of AGA and AGG by glyT(SuAGA/G) tRNA as well as UGG by glyT(SuUGG-8) tRNA is unaffected whereas suppression of UGG by glyT(SuUGA/G) or glyV(SuUGA/G) tRNA is decreased in the presence of an rpsD mutation. The effects on suppressor tRNA are thus not correlated with the ribosomal ambiguity (Ram) phenotype of the rpsD mutants used in this study. It is suggested that the mutationally altered ribosomes are changed in functional interactions with the suppressor tRNA itself rather than with the competing translational release factor(s) or cognate aminoacyl tRNA. The structure of suppressor tRNA, particularly the anticodon loop, and the suppressed codon as well as the codon context determine the allele specific functional interactions with these ribosomal mutations.
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| 4. |
- Kirsebom, Leif A, et al.
(författare)
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Involvement of ribosomal protein L7/L12 in control of translational accuracy
- 1985
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 82:3, s. 717-721
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Tidskriftsartikel (refereegranskat)abstract
- The effects of two mutations, which map at the rplL locus and both give a changed 50S ribosomal protein L7/L12, were studied. Both mutations are associated with an increased misreading of all three nonsense codons in vivo and ribosomes from the mutants give an increased misreading of the phenylalanine codon UUU by tRNALeu in vitro. The rplL-associated misreading in vitro is not limited to a particular type of mRNA or tRNA. Results from a translational proofreading assay, using mutant ribosomes, suggest that protein L7/L12 is involved in the control of translational accuracy by contributing to the efficiency of a translational proofreading step(s).
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| 5. |
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| 6. |
- Altman, S, et al.
(författare)
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Catalysis by the RNA subunit of RNase P
- 1989
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Ingår i: Gene. - : Elsevier BV. - 0378-1119 .- 1879-0038. ; 82:1, s. 63-64
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Forskningsöversikt (refereegranskat)abstract
- RNase P, an enzyme that contains both RNA and protein components, cleaves tRNA precursors to generate mature 5' termini. The catalytic activity of RNase P resides in the RNA component, with the protein cofactor affecting the rate of the cleavage reaction. The reaction is also influenced by the nature of the tRNA substrate.
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| 7. |
- Altman, S, et al.
(författare)
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Cleavage of RNA by RNase P from E. coli
- 1987
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Ingår i: Molecular Biology of RNA: New Perspectives. - : Academic Press.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Bilgin, Neş'e, et al.
(författare)
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Mutations in ribosomal proteins L7/L12 perturb EF-G and EF-Tu functons
- 1988
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Ingår i: Biochimie. - : Elsevier BV. - 0300-9084 .- 1638-6183. ; 70:5, s. 611-618
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Tidskriftsartikel (refereegranskat)abstract
- In vitro cycling rates of E. coli ribosomes and of elongation factors EF-Tu and EF-G have been obtained and these are compatible with translation rates in vivo. We show that the rate of translocation is faster than 50 s-1 and therefore that the EF-G function is not a rate limiting step in protein synthesis. The in vivo phenotype of some L7/L12 mutants could be accounted for by perturbed EF-Tu as well as EF-G functions. The S12 mutants that we studied were, in contrast, only perturbed in their EF-Tu function, while their EF-G interaction was not impaired in relation to wild type ribosomes.
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| 9. |
- Kirsebom, Leif A, et al.
(författare)
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Differential effects of mutations in the protein and RNA moieties of RNase P on the efficiency of suppression by various tRNA suppressors
- 1988
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 204:4, s. 879-888
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the efficiency of suppression by tRNA suppressors in vivo in strains of Escherichia coli that harbor a mutation in the rnpA gene, the gene for the protein component (C5) of RNase P, and in strains that carry several different alleles of the rnpB gene, the gene for the RNA component (M1) of RNase P. Depending on the genetic background, different efficiencies of suppression by the various tRNA suppressors were observed. Thus, mutations in rnpA have separable and distinct effects from mutations in rnpB on the processing of tRNA precursors by RNase P. In addition, the efficiency of suppression by several derivatives of E. coli tRNA(Tyr) Su3 changed as the genetic background was altered.
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| 10. |
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| 11. |
- Kirsebom, Leif A, et al.
(författare)
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Reaction in vitro of some mutants of RNase P with wild-type and temperature-sensitive substrates
- 1989
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 207:4, s. 837-840
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The reaction of wild-type and two mutant derivatives of RNase P have been examined with wild-type and mutant substrates. We show that a mutant derivative of tRNA(Tyr)Su3, tRNA(Tyr)Su3A15, in which the G15.C48(57) base-pair essential for folding of the tRNA moiety is altered, is a temperature-sensitive suppressor in vivo. The precursor to tRNA(Tyr)Su3A15 is cleaved in a temperature-sensitive manner in vitro by RNase P and with a higher Km compared to the precursor to tRNA(Tyr)Su3. The precursor to tRNA(Tyr)Su3A2, another temperature-sensitive suppressor in vivo in which the G2.C71(80) base-pair in the acceptor stem is changed to A2.C71(80), behaves like the precursor to tRNA(Tyr)Su3 in vitro; that is, it is not cleaved in a temperature-sensitive manner. Therefore, there are at least two ways in which a suppressor tRNA can acquire a temperature-sensitive phenotype in vivo. One of the mutant derivatives of RNase P we have tested, rnpA49, which affects the protein cofactor of the enzyme, has a decreased kcat compared to wild-type, which can explain its phenotype in vivo.
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| 12. |
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