I2CT

@article{,

title = {Mutation and evolution of the magnesium-binding site of a class II aminoacyl-tRNA synthetase},

author = {L Ador and S Jaeger and R Geslain and F Martin and J Cavarelli and G Eriani},

url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=15170340},

isbn = {15170340},

year  = {2004},

date = {2004-01-01},

journal = {Biochemistry},

volume = {43},

number = {22},

pages = {7028-7037},

abstract = {Aminoacyl-tRNA synthetases contain one or three Mg(2+) ions in their catalytic sites. In addition to their role in ATP binding, these ions are presumed to play a role in catalysis by increasing the electropositivity of the alpha-phosphate and stabilizing the pentavalent transition state. In the class II aaRS, two highly conserved carboxylate residues have been shown to participate with Mg(2+) ions in binding and coordination. It is shown here that these carboxylate residues are absolutely required for the activity of Saccharomyces cerevisiae aspartyl-tRNA synthetase. Mutants of these residues exhibit pleiotropic effects on the kinetic parameters suggesting an effect at an early stage of the aminoacylation reaction, such as the binding of ATP, Mg(2+), aspartic acid, or the amino acid activation. Despite genetic selections in an APS-knockout yeast strain, we were unable to select a single active mutant of these carboxylate residues. Nevertheless, we isolated an intragenic suppressor from a combinatorial library. The active mutant showed a second substitution close to the first one, and exhibited a significant increase of the tRNA aminoacylation rate. Structural analysis suggests that the acceptor stem of the tRNA might be repositioned to give a more productive enzyme:tRNA complex. Thus, the initial defect of the activation reaction was compensated by a significant increase of the aminoacylation rate that led to cellular complementation.},

note = {0006-2960 

Journal Article},

keywords = {Acylation Adenosine Triphosphate/metabolism Amino Acid Substitution Aspartate-tRNA Ligase/chemistry/genetics/*metabolism Aspartic Acid/metabolism Binding Sites Catalytic Domain Cell Death Combinatorial Chemistry Techniques Comparative Study *Evolution, Asp/metabolism  Saccharomyces cerevisiae/*enzymology  Support, ERIANI, Molecular  Kinetics  Magnesium/*metabolism  Mutagenesis, Non-U.S. Gov't  Transfection, Site-Directed  Mutation/*genetics  Peptide Library  Protein Binding  Protein Conformation  RNA, Transfer, Unité ARN},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {A single internal ribosome entry site containing a G quartet RNA structure drives fibroblast growth factor 2 gene expression at four alternative translation initiation codons},

author = {S Bonnal and C Schaeffer and L Creancier and S Clamens and H Moine and A C Prats and S Vagner},

url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12857733},

isbn = {12857733},

year  = {2003},

date = {2003-01-01},

journal = {J Biol Chem},

volume = {278},

number = {41},

pages = {39330-39336},

abstract = {The 484-nucleotide (nt) alternatively translated region (ATR) of the human fibroblast growth factor 2 (FGF-2) mRNA contains four CUG and one AUG translation initiation codons. Although the 5'-end proximal CUG codon is initiated by a cap-dependent translation process, the other four initiation codons are initiated by a mechanism of internal entry of ribosomes. We undertook here a detailed analysis of the cis-acting elements defining the FGF-2 internal ribosome entry site (IRES). A thorough deletion analysis study within the 5'-ATR led us to define a 176-nt region as being necessary and sufficient for IRES function at four codons present in a downstream 308-nt RNA segment. Unexpectedly, a single IRES module is therefore responsible for translation initiation at four distantly localized codons. The determination of the FGF-2 5'-ATR RNA secondary structure by enzymatic and chemical probing experiments showed that the FGF-2 IRES contained two stem-loop regions and a G quartet motif that constitute novel structural determinants of IRES function.},

note = {0021-9258 

Journal Article},

keywords = {Alternative Splicing  Base Sequence  Cell Line  Codon, Complementary/genetics  Fibroblast Growth Factor 2/*genetics  Gene Expression  Human  Molecular Sequence Data  Nucleic Acid Conformation  Peptide Chain Initiation  RNA, Initiator/genetics  DNA, Messenger/*chemistry/*genetics  Ribosomes/*metabolism  Sequence Deletion  Support, Non-U.S. Gov't  Transfection, Unité ARN},

pubstate = {published},

tppubtype = {article}

}