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)

The solution structure of Escherichia coli tRNA(3Thr) (anticodon GGU) and the residues of this tRNA in contact with the alpha 2 dimeric threonyl-tRNA synthetase were studied by chemical and enzymatic footprinting experiments. Alkylation of phosphodiester bonds by ethylnitrosourea and of N-7 positions in guanosines and N-3 positions in cytidines by dimethyl sulphate as well as carbethoxylation of N-7 positions in adenosines by diethyl pyrocarbonate were conducted on different conformers of tRNA(3Thr). The enzymatic structural probes were nuclease S1 and the cobra venom ribonuclease. Results will be compared to those of three other tRNAs, tRNA(Asp), tRNA(Phe) and tRNA(Trp), already mapped with these probes. The reactivity of phosphates towards ethylnitrosourea of the unfolded tRNA was compared to that of the native molecule. The alkylation pattern of tRNA(3Thr) shows some similarities to that of yeast tRNA(Phe) and mammalian tRNA(Trp), especially in the D-arm (positions 19 and 24) and with tRNA(Trp), at position 50, the junction between the variable region and the T-stem. In the T-loop, tRNA(3Thr), similarly to the three other tRNAs, shows protections against alkylation at phosphates 59 and 60. However, tRNA(3Thr) is unique as far as very strong protections are also found for phosphates 55 to 58 in the T-loop. Compared with yeast tRNA(Asp), the main differences in reactivity concern phosphates 19, 24 and 50. Mapping of bases with dimethyl sulphate and diethyl pyrocarbonate reveal conformational similarities with yeast tRNA(Phe). A striking conformational feature of tRNA(3Thr) is found in the 3'-side of its anticodon stem, where G40, surrounded by two G residues, is alkylated under native conditions, in contrast to other G residues in stem regions of tRNAs which are unreactive when sandwiched between two purines. This data is indicative of a perturbed helical conformation in the anticodon stem at the level of the 30-40 base pairs. Footprinting experiments, with chemical and enzymatic probes, on the tRNA complexed with its cognate threonyl-tRNA synthetase indicate significant protections in the anticodon stem and loop region, in the extra-loop, and in the amino acid accepting region. The involvement of the anticodon of tRNA(3Thr) in the recognition process with threonyl-tRNA synthetase was demonstrated by nuclease S1 mapping and by the protection of G34 and G35 against alkylation by dimethyl sulphate. These data are discussed in the light of the tRNA/synthetase recognition problem and of the structural and functional properties of the tRNA-like structure present in the operator region of the thrS mRNA.
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PMID:Tertiary structure of Escherichia coli tRNA(3Thr) in solution and interaction of this tRNA with the cognate threonyl-tRNA synthetase. 245

The present study was designed to investigate whether heparin-binding epidermal growth factor-like growth factor and its related peptides are expressed in response to gastrin in rat stomach. Rat gastrin-17I (2.5 nmol/kg/hour) or gastrin-17I plus gastrin receptor antagonist, L-740,093 (2.0 mg/kg/hour), was injected intravenously into male Sprague-Dawley rats. RNA was extracted from oxyntic mucosa, and heparin-binding epidermal growth factor-like growth factor and related peptide gene expression was estimated using a ribonuclease protection assay. The level of transforming growth factor-alpha mRNA did not change at any time point during the experiment. In contrast, the levels of heparin-binding epidermal growth factor-like growth factor and amphiregulin mRNA were significantly increased within 3 hours following gastrin infusion and reached maximum levels 6 and 12 hours later, respectively. Continuous infusion of gastrin significantly increased oxyntic mucosal proliferation. Gastrin receptor antagonist significantly inhibited gastrin-induced heparin-binding epidermal growth factor-like growth factor and amphiregulin gene expression and gastrin-induced oxyntic mucosal proliferation. These findings indicate that heparin-binding epidermal growth factor-like growth factor and amphiregulin genes are induced by gastrin and that they play a role in the trophic action of gastrin on oxyntic mucosa.
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PMID:Induction of heparin binding epidermal growth factor-like growth factor and amphiregulin mRNAs by gastrin in the rat stomach. 920 88

1. Inhibition of gastric acid secretion by proton pump inhibitors like omeprazole increases the synthesis and secretion of the pyloric antral hormone gastrin. We report here how omeprazole influences the conversion of the gastrin precursor to its final products, and the abundance of mRNAs encoding proteins associated with progastrin processing in rat antral mucosa. 2. Progastrin processing was studied using a pulse-chase protocol in antral mucosa, incubated in vitro, from rats treated with omeprazole for up to 5 days. Labelled peptides were detected by on-line scintillation counting after immunoprecipitation and HPLC. The mRNAs encoding prohormone-processing enzymes were identified by Northern blot, polymerase chain reaction or ribonuclease protection assay, and their cellular origins identified by immunocytochemistry. 3. Cleavage of [3H]- and [35S]-labelled progastrins at Arg-94-95 or Arg-57-58, and amidation at Phe-92 were not influenced by pretreatment with omeprazole. In contrast, cleavage of G34 (the thirty-four amino acid amidated gastrin) at Lys-74-75 to give G17 (the seventeen amino acid amidated gastrin), and of G34-Gly to G17-Gly (G34 and G17 with COOH-terminal glycine), was increased 3-fold after treatment with omeprazole for either 1 or 5 days. 4. Approximately 20% of newly synthesized amidated and Gly-extended gastrins were secreted within 240 min of the labelling period in omeprazole-treated samples, but secretion of labelled gastrins from control tissue was undetectable over a comparable period. 5. The amidating enzyme, peptidyglycine alpha-amidating mono-oxygenase (PAM), the prohormone convertases PC1/3, PC2, PC5 and the PC2 chaperone 7B2 were localized to rat antral gastrin cells by immunocytochemistry. The relative abundance of mRNA species encoding 7B2, PC5 and PAM were unchanged after treatment with omeprazole for 5 days, whereas gastrin, PC1/3 and PC2 mRNAs are known to increase at this time. 6. The main consequence of increased cleavage at Lys-74-75 is the production of G17 and G17-Gly at the expense of G34 and G34-Gly, respectively. The latter have longer plasma half-lives, and so their increased cleavage may serve to limit the rise in plasma gastrin concentration after inhibition of acid secretion. Changes in the abundance of mRNAs encoding prohormone-processing enzymes cannot account for the rapidity of the changes in cleavage of progastrin at Lys residues after omeprazole.
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PMID:Regulation by gastric acid of the processing of progastrin-derived peptides in rat antral mucosa. 926 20