scholarly journals The Mere Lack of rT Modification in Initiator tRNA Does Not Facilitate Formylation-Independent Initiation inEscherichia coli

2001 ◽  
Vol 183 (24) ◽  
pp. 7397-7402 ◽  
Author(s):  
Swapna Thanedar ◽  
T. K. Dineshkumar ◽  
Umesh Varshney
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Normal Growth ◽  
Assay System ◽  
Inescherichia Coli ◽  
Initiator Trna

ABSTRACT Formylation of initiator methionyl-tRNA is essential for normal growth of eubacteria. However, under special conditions, it has been possible to initiate protein synthesis with unformylated initiator tRNA even in eubacteria. Earlier studies suggested that the lack of ribothymidine (rT) modification in initiator tRNA may facilitate initiation in the absence of formylation. In this report we show, by using trmA strains of Escherichia coli(defective for rT modification) and a sensitive in vivo initiation assay system, that the lack of rT modification in the initiators is not sufficient to effect formylation-independent initiation of protein synthesis.

scholarly journals LOCALIZED MUTAGENESIS FOR THE ISOLATION OF TEMPERATURE-SENSITIVE MUTANTS OF ESCHERICHIA COLI AFFECTED IN PROTEIN SYNTHESIS

Genetics ◽  
1979 ◽  
Vol 91 (2) ◽  
pp. 215-227
Author(s):  
W Scott Champney
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Temperature Sensitive ◽  
Chromosomal Locus ◽  
Ribosomal Subunits ◽  
Prolonged Incubation ◽  
Temperature Sensitive Mutants ◽  
Inhibition Of Growth ◽  
Localized Mutagenesis

ABSTRACT Two variations of the method of localized mutagenesis were used to introduce mutations into the 72 min region of the Escherichia coli chromosome. Twenty temperature-sensitive mutants, with linkage to markers in this region, have been examined. Each strain showed an inhibition of growth in liquid medium at 44°, and 19 of the mutants lost viability upon prolonged incubation at this temperature. A reduction in the rate of in vivo RNA and protein synthesis was observed for each mutant at 44°, relative to a control strain. Eleven of the mutants were altered in growth sensitivity or resistance to one or more of three ribosomal antibiotics. The incomplete assembly of ribosomal subunits was detected in nine strains grown at 44°. The characteristics of these mutants suggest that many of them are altered in genes for translational or transcriptional components, consistent with the clustering of these genes at this chromosomal locus.

scholarly journals Composition of the λ plasmid heritable replicationcomplex

2002 ◽  
Vol 364 (3) ◽  
pp. 857-862 ◽  
Author(s):  
Katarzyna POTRYKUS ◽  
Sylwia BARAŃSKA ◽  
Alicja WĘGRZYN ◽  
Grzegorz WĘGRZYN
Keyword(s):  
Escherichia Coli ◽  
Saccharomyces Cerevisiae ◽  
Protein Synthesis ◽  
Plasmid Dna ◽  
Pcr Analysis ◽  
Cross Linking ◽  
Bacteriophage Λ ◽  
Yeast Saccharomyces Cerevisiae ◽  
Replication Complex

Previous studies indicated during replication of plasmids derived from bacteriophage λ (the so-called λ plasmids), that, once assembled, replication complex can be inherited by one of the two daughter plasmid copies after each replication round, and may function in subsequent replication rounds. It seems that similar processes occur during replication of other DNA molecules, including chromosomes of the yeast Saccharomyces cerevisiae. However, apart from some suggestions based on genetic experiments, composition of the λ heritable replication complex remains unknown. In amino acid-starved Escherichia coli relA mutants, replication of λ plasmid DNA is carried out exclusively by the heritable replication complex as assembly of new complexes is impaired due to inhibition of protein synthesis. Here, using a procedure based on in vivo cross-linking, cell lysis, immunoprecipitation with specific sera, de-cross-linking and PCR analysis, we demonstrate that the λ heritable replication complex consists of O, P, DnaB and, perhaps surprisingly, DnaK proteins.

scholarly journals Lowering S-Adenosylmethionine Levels inEscherichia coli Modulates C-to-T Transition Mutations

2001 ◽  
Vol 183 (3) ◽  
pp. 921-927 ◽  
Author(s):  
Georgina Macintyre ◽  
C. Victoria Atwood ◽  
Claire G. Cupples
Keyword(s):  
Escherichia Coli ◽  
Dna Methylation ◽  
Genomic Dna ◽  
Synthetase Activity ◽  
Inescherichia Coli ◽  
Genome Methylation ◽  
Sam Synthetase ◽  
Methyl Cytosine

ABSTRACT Deoxycytosine methylase (Dcm) enzyme activity causes mutagenesis in vitro either directly by enzyme-induced deamination of cytosine to uracil in the absence of the methyl donor,S-adenosylmethionine (SAM), or indirectly through spontaneous deamination of [5-methyl]cytosine to thymine. Using a Lac reversion assay, we investigated the contribution of the first mechanism to Dcm mutagenesis in vivo by lowering the levels of SAM.Escherichia coli SAM levels were lowered by reducing SAM synthetase activity via the introduction of a metK84 allele or by hydrolyzing SAM using the bacteriophage T3 SAM hydrolase. ThemetK84 strains exhibited increased C-to-T mutagenesis. Expression of the T3 SAM hydrolase gene, under the control of the arabinose-inducible PBAD promoter, effectively reduced Dcm-mediated genomic DNA methylation. However, increased mutagenesis was not observed until extremely high arabinose concentrations were used, and genome methylation at Dcm sites was negligible.

scholarly journals Protein Synthesis in Escherichia coli with Mischarged tRNA

2003 ◽  
Vol 185 (12) ◽  
pp. 3524-3526 ◽  
Author(s):  
Bokkee Min ◽  
Makoto Kitabatake ◽  
Carla Polycarpo ◽  
Joanne Pelaschier ◽  
Gregory Raczniak ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Elongation Factor ◽  
Trna Synthetase ◽  
Wild Type ◽  
Wild Type Level ◽  
E Coli ◽  
Missense Mutant ◽  
Tryptophan Synthetase

ABSTRACT Two types of aspartyl-tRNA synthetase exist: the discriminating enzyme (D-AspRS) forms only Asp-tRNAAsp, while the nondiscriminating one (ND-AspRS) also synthesizes Asp-tRNAAsn, a required intermediate in protein synthesis in many organisms (but not in Escherichia coli). On the basis of the E. coli trpA34 missense mutant transformed with heterologous ND-aspS genes, we developed a system with which to measure the in vivo formation of Asp-tRNAAsn and its acceptance by elongation factor EF-Tu. While large amounts of Asp-tRNAAsn are detrimental to E. coli, smaller amounts support protein synthesis and allow the formation of up to 38% of the wild-type level of missense-suppressed tryptophan synthetase.

scholarly journals Directed evolution of rRNA improves translation kinetics and recombinant protein yield

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fan Liu ◽  
Siniša Bratulić ◽  
Alan Costello ◽  
Teemu P. Miettinen ◽  
Ahmed H. Badran
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Bacterial Population ◽  
Protein Yield ◽  
Rrna Sequence ◽  
Evolutionary Trajectory ◽  
Noncanonical Amino Acids ◽  
Rate Limiting

AbstractIn bacteria, ribosome kinetics are considered rate-limiting for protein synthesis and cell growth. Enhanced ribosome kinetics may augment bacterial growth and biomanufacturing through improvements to overall protein yield, but whether this can be achieved by ribosome-specific modifications remains unknown. Here, we evolve 16S ribosomal RNAs (rRNAs) from Escherichia coli, Pseudomonas aeruginosa, and Vibrio cholerae towards enhanced protein synthesis rates. We find that rRNA sequence origin significantly impacted evolutionary trajectory and generated rRNA mutants with augmented protein synthesis rates in both natural and engineered contexts, including the incorporation of noncanonical amino acids. Moreover, discovered consensus mutations can be ported onto phylogenetically divergent rRNAs, imparting improved translational activities. Finally, we show that increased translation rates in vivo coincide with only moderately reduced translational fidelity, but do not enhance bacterial population growth. Together, these findings provide a versatile platform for development of unnatural ribosomal functions in vivo.

Sign in / Sign up

Export Citation Format

Share Document