Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.3 (RNase T1)
 1,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The accessibility of nucleotides in Escherichia coli tRNAfMet to chemical and enzymatic probes in the presence and absence of methionyl-tRNA synthetase has been investigated. Dimethyl sulfate was used to probe the reactivity of cytosine and guanosine residues. The N-3 position of the wobble anticodon base, C34, was strongly protected from methylation in the tRNA-synthetase complex. A synthetase-induced conformational change in the anticodon loop was suggested by the enhanced reactivity of C32 in the presence of enzyme. Cytosine residues in the dihydrouridine loop and in the 3'-terminal CCA sequence showed little or no change in reactivity. Methylation of the N-7 position of guanosine residues G42, G52, and G70 was partially inhibited by the synthetase. Nuclease digestion of tRNAfMet with alpha-sarcin in the presence of 1-2 mM Mg2+ resulted in cleavage mainly at C71 in the acceptor stem and was strongly inhibited by synthetase. Other nuclease digestion experiments using the single strand specific nucleases RNase A and RNase T1 revealed weak protection of nucleotides in the D loop and strong protection of nucleotides in the anticodon on complex formation. The present data, together with previous structure-function studies on this system, indicate strong binding of methionyl-tRNA synthetase to the anticodon of tRNAfMet, leading to a change in the conformation of the anticodon loop and stem. We propose that this, in turn, produces more distant, and possibly relatively subtle, conformational changes in other parts of the tRNA structure that ultimately lead to proper orientation of the 3' terminus of the tRNA with respect to the active site of the enzyme.
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PMID:Study of the interaction of Escherichia coli methionyl-tRNA synthetase with tRNAfMet using chemical and enzymatic probes. 309 57

An eicosanucleotide C--G--C--G--G--G--G--U--G--G--A--G--C--A--G--C--C--U--G--Gp corresponding to the bases 1--20 of the nascent sequence for the Escherichia coli tRNAfMet has been synthesized by the joining of the chemically synthesized oligonucleotides C--G--C--G, G--G--G--U--G--G and A--G--C--A--G--C--C--U--G--Gp using RNA ligase from T4-infected E. coli. The hexanucleotide and decanucleotide were phosphorylated with polynucleotide kinase and [gamma-32P]ATP prior to the joining reactions. The decanucleotide and eicosanucleotide were reconstituted respectively with the 3'-three-quarter molecule obtained by limited digestion with RNase T1 of the natural tRNAfMet from E. coli and the activity of the complex as a methionine acceptor was tested using purified methionyl-tRNA synthetase from E. coli. The amino acid acceptor activity of the reconstituted molecules was 11% and 84% with respect to that of the intact tRNAfMet.
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PMID:Synthesis of 5' fragments of formylmethionine transfer ribonucleic acid and their reconstitution with a natural three-quarter molecule. 615 76