Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.1 (S1 nuclease)
 3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nucleotide sequence of a cDNA coding human threonyl-tRNA synthetase has been determined. The predicted protein sequence is highly homologous to that of the yeast cytoplasmic, yeast mitochondria and Escherichia coli threonyl-tRNA synthetases. In particular, the three structural motifs recently shown to be common to class II aminoacyl-tRNA synthetases are present in the threonyl-tRNA synthetases from all sources. Primer extension and S1 nuclease analyses indicate that transcription initiates approximately 220-230 nucleotides upstream of the putative initiator methionine codon. This region contains a 10-nucleotide interrupted inverted repeat flanked by a 13-nucleotide interrupted direct repeat.
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PMID:Nucleotide and deduced amino acid sequence of human threonyl-tRNA synthetase reveals extensive homology to the Escherichia coli and yeast enzymes. 203 77

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 genes coding for threonyl-tRNA synthetase (thrS), translation initiation factor 3 (infC) and ribosomal protein L20 (rplT) are clustered in the Escherichia coli genome. Previous studies had suggested the possibility that the expression of these genes is coupled. The transcriptional events in this operon have now been examined by S1 nuclease mapping and promoter fusion studies. The results indicate that infC-containing mRNAs are initiated from three separate promoters. Two of these are located in the protein-coding region of thrS and one, P12, is the major promoter at all growth rates tested. In addition, there is co-transcription of thrS and infC from the thrS promoter (PT). A single promoter for thrS has been mapped approx. 170 nucleotides upstream from its translation initiation site. Another promoter has been located within the infC-coding region. It is separated from the next downstream gene, rplT, by a transcription end point. However, termination at this region is only 50-70% efficient and transcripts starting at this promoter can read through into rplT. These findings demonstrate that the pattern of transcription in this operon is highly complex and the mRNA levels for each of the genes is determined by a variety of factors, including multiple promoters, co-transcription and readthrough of transcription termination signals.
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PMID:Transcriptional patterns for the thrS-infC-rplT operon of Escherichia coli. 283 94