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Adaptation proceeds through the selection of mutations. The distribution of mutant fitness effect and the forces shaping this distribution are therefore keys to predict the evolutionary fate of organisms and their constituents such as enzymes. Here, by producing and sequencing a comprehensive collection of 10,000 mutants, we explore the mutational landscape(More)
Peptidyl-tRNA hydrolase activity from Escherichia coli ensures the recycling of peptidyl-tRNAs produced through abortion of translation. This activity, which is essential for cell viability, is carried out by a monomeric protein of 193 residues. The structure of crystalline peptidyl-tRNA hydrolase could be solved at 1.2 A resolution. It indicates a single(More)
To carry initiator Met-tRNA(i)(Met) to the small ribosomal subunit, eukaryal and archaeal cells use a heterotrimeric factor called e/aIF2. These cells also possess a homologue of bacterial IF2 called e/aIF5B. Several results indicate that the mode of action of e/aIF5B resembles some function of bacterial IF2. The e/aIF5B factor promotes the joining of(More)
Eukaryotic and archaeal translation initiation factor 2 (e/aIF2) is a heterotrimeric GTPase that has a crucial role in the selection of the correct start codon on messenger RNA. We report the 5-Å resolution crystal structure of the ternary complex formed by archaeal aIF2 from Sulfolobus solfataricus, the GTP analog GDPNP and methionylated initiator tRNA.(More)
Methionine is the universal translation start but the first methionine is removed from most mature proteins. This review focuses on our present knowledge of the five enzymes sustaining the methionine pathway in translation initiation in Escherichia coli: methionyl-tRNA synthetase, methionyl-tRNA(fMet) formyltransferase, peptidyl-tRNA hydrolase, peptide(More)
Strains of the yeast Kluyveroayces lactis that produce killer-toxin have been found to contain two linear dsDNA plasaids, kj (8.9 Kb) and k2 (13.4 8b). The four transcribed open reading fraaes of plasaid kj contain no recognisable yeast nuclear expression signals. Moreover, a toxin subunit gene fused with the lacZ gene of Bscherichia coli is not detectably(More)
The DNA sequence of a 2,100-bp region containing the argE gene from Escherichia coli has been determined. The nucleotide sequence of the ppc-argE intergenic region was also solved and shown to contain six tandemly repeated REP sequences. Moreover, the oxyR gene has been mapped on the E. coli chromosome and shown to flank the arg operon. The codon(More)
The heterotrimeric factor e/aIF2 plays a central role in eukaryotic/archaeal initiation of translation. By delivering the initiator methionyl-tRNA to the ribosome, e/aIF2 ensures specificity of initiation codon selection. The three subunits of aIF2 from the hyperthermophilic archaeon Pyrococcus abyssi could be overproduced in Escherichia coli. The beta and(More)
The 3D structure of monomeric C-truncated Escherichia coli methionyl-tRNA synthetase, a class 1 aminoacyl-tRNA synthetase, has been solved at 2.0 A resolution. Remarkably, the polypeptide connecting the two halves of the Rossmann fold exposes two identical knuckles related by a 2-fold axis but with zinc in the distal knuckle only. Examination of available(More)
Eukaryotic and archaeal initiation factors 2 (e/aIF2) are heterotrimeric proteins (alphabetagamma) carrying methionylated initiator tRNA to the small subunit of the ribosome. The three-dimensional structure of aIF2gamma from the Archaea Pyrococcus abyssi was previously solved. This subunit forms the core of the heterotrimer. The alpha and beta subunits bind(More)