Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

From a strain of Escherichia coli with two copies of the tryptophan (trp) operon and one copy of the lactose (lac) operon, under control of one of the trp regulatory elements, we have isolated a mutant which does not grow in a medium containing 19 amino acids, unless tryptophan is added, and which cannot ferment lactose. The apparent pleiotropic nature of the mutation(s) is indicated by the very slow growth of mutant bacteria on minimal-medium agar supplemented with glucose and tryptophan. The amount of the trp enzymes (anthranilate synthetase and tryptophan synthetase) and trp messenger ribonucleic acid is reduced several-fold in the mutant compared to the isogenic wild-type strain, whereas the enzymes tryptophanyl-transfer ribonucleic acid synthetase and glucose 6-phosphate dehydrogenase remain the same. The incorporation of radioactive label into pulse-labeled but not into stable ribonucleic acid is significantly lower. Our results suggest that in the mutant organism the control of transcription of some operons, including the trp operon, is modified. An alternative explanation is that mutant bacteria contain a ribonuclease with increased activity for some messenger ribonucleic acid species.
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PMID:Escherichia coli mutant strain with altered expression of the tryptophan operon: isolation and preliminary characterization. 37 67

Transfer RNA molecules have been labeled with 32P at the 5' or 3' end and digested with cobra venom ribonuclease, which preferentially cuts double-stranded regions. The products of yeast tRNAPhe and tRNAVal were analyzed by high-resolution gel electrohporesis. In the free state, these tRNAs were cut predominantly in the acceptor and anticodon stems. Minor cuts occurred in the T psi stem in tRNAVal. The topography of zones interacting with their cognate synthetases was studied by determining the tRNA regions shielded by protein. Nearly 100% protection was found in the anticodon and acceptor stem of tRNAVal, while in tRNAPhe only the stem of the anticodon was protected. Noncognate interactions between tRNAPhe and tryptophanyl-tRNA synthetase from beef pancreas were examined. The beef enzyme did not protect tRNAPhe despite the fact that efficient misaminoacylation occurred. The pattern of shielding obtained for each tRNA-synthetase complex was compared with the results of direct ultraviolet cross-linking experiments with these complexes.
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PMID:Partial digestion of tRNA--aminoacyl-tRNA synthetase complexes with cobra venom ribonuclease. 701 69

The primary structure of the gene encoding Bombyx mori glycyl-tRNA synthetase was determined by sequence analysis of one cDNA and two genomic clones. The sequence of the protein deduced from the nucleotide sequence was verified by sequence analysis of eight peptides. The M(r) 77,667 protein is encoded in a single open reading frame of 2061 nucleotides. There are no introns in the gene. The deduced protein sequence has no obvious similarity to Escherichia coli glycyl-tRNA synthetase but contains a sequence in its amino terminus that is similar to a sequence found in the Drosophila melanogaster and human glutamyl-tRNA synthetases, the hamster and human histidyl-tRNA synthetases, bovine tryptophanyl-tRNA synthetase, and the mammalian peptide chain release factor. The B. mori glycyl-tRNA synthetase also has sequence similarity with the Saccharomyces cerevisiae (cytoplasmic and mitochondrial), E. coli, and human threonyl-tRNA synthetases. This sequence similarity occurs in a sequence motif that is characteristic of other class II aminoacyl-tRNA synthetases. Two transcription start sites approximately 100 nucleotides apart were identified by ribonuclease mapping. One of the transcription start sites is used preferentially in the posterior silk gland. The peak in mRNA accumulation occurs 80-100 h prior to the peak in glycyl-tRNA synthetase activity and enzyme protein.
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PMID:Primary structure of the gene for glycyl-tRNA synthetase from Bombyx mori. 846 96