Joël Caillet

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Accurate translation of the genetic code depends on the ability of aminoacyl-tRNA synthetases to distinguish between similar amino acids. In order to investigate the basis of amino acid recognition and to understand the role played by the zinc ion present in the active site of threonyl-tRNA synthetase, we have determined the crystal structures of complexes(More)
Threonyl-tRNA synthetase from Escherichia coli represses the translation of its own mRNA by binding to the operator region located upstream from the ribosome binding site. The operator contains two stemloop structures which interact specifically with the homodimeric enzyme. Here, we provide in vitro and in vivo evidence that these two stem-loop structures(More)
We have isolated an Escherichia coli gene which, when overexpressed, is able to complement the permeability defects of a vancomycin-susceptible mutant. This gene, designated sanA, is located at min 47 of the E. coli chromosome and codes for a 20-kDa protein with a highly hydrophobic amino-terminal segment. A strain carrying a null mutation of the sanA gene,(More)
Isopentenyl diphosphate:dimethylallyl diphosphate (IPP:DMAPP) isomerase catalyses a crucial activation step in the isoprenoid biosynthesis pathway. This enzyme is responsible for the isomerization of the carbon-carbon double bond of IPP to create the potent electrophile DMAPP. DMAPP then alkylates other molecules, including IPP, to initiate the(More)
We describe a methodology which allows the introduction of a photoactivatable azido group at specific internal positions of any RNA in order to identify the neighboring elements of an interacting protein. The first step involves site-directed modification of the target RNA with an antisense oligodeoxyribonucleotide bearing, at its 3' or 5' phosphate, a(More)
MnmC catalyses the last two steps in the biosynthesis of 5-methylaminomethyl-2-thiouridine (mnm(5)s(2)U) in tRNA. Previously, we reported that this bifunctional enzyme is encoded by the yfcK open reading frame in the Escherichia coli K12 genome. However, the mechanism of its activity, in particular the potential structural and functional dependence of the(More)
Clostridium difficile is an emergent human pathogen and the most common cause of nosocomial diarrhea. Our recent data strongly suggest the importance of RNA-based mechanisms for the control of gene expression in C. difficile. In an effort to understand the function of the RNA chaperone protein Hfq, we constructed and characterized an Hfq-depleted strain in(More)
The gene encoding the bifunctional enzyme MnmC that catalyzes the two last steps in the biosynthesis of 5-methylaminomethyl-2-thiouridine (mnm5s2U) in tRNA has been previously mapped at about 50 min on the Escherichia coli K12 chromosome, but to date the identity of the corresponding enzyme has not been correlated with any of the known open reading frames(More)
Previous work showed that E coli threonyl-tRNA synthetase (ThrRS) binds to the leader region of its own mRNA and represses its translation by blocking ribosome binding. The operator consists of four distinct domains, one of them (domain 2) sharing structural analogies with the anticodon arm of the E coli tRNA(Thr). The regulation specificity can be switched(More)
The expression of the gene encoding Escherichia coli threonyl-tRNA synthetase (ThrRS) is negatively autoregulated at the translational level. ThrRS binds to its own mRNA leader, which consists of four structural and functional domains: the Shine-Dalgarno (SD) sequence and the initiation codon region (domain 1); two upstream hairpins (domains 2 and 4)(More)