Aminoacyl-t-RNA

An interest in ester migration in the monoacyl derivatives of the vicinal-diol grouping in ribofuranosides stemmed from a desire to establish the position of attachment of the aminoacyl group to the terminal adenosine residue of aminoacyl-(t-RNA),569-571 and also from the necessity of producing suitably protected intermediates for oligoribonucleotide syntheses. That a facile equilibrium can exist is shown by the fact that, on being kept, an ethanol solution of... 

There are numerous examples of the inhibition of biosynthesis by fungicides. Some fungicidal secondary metabolites, like cyclohexi-mide and blasticidine, interfere with synthesis of peptide bonds at the ribosomal site (2). Another, kasugamycine, influences aminoacyl-t-RNA/ribosome interactions (3). Finally, another mechanism inhibiting protein biosynthesis is realized on the DNA/RNA- level by the... 

Other affinity labels (derivatives of aminoacyl-t-RNA, antibiotics, me nger RNA or of GTP) were also used in studying specific binding sites of ribosomes... 

Knorre, D. G., Lavrik, O. I. Affinity labeling of aminoacyl-t-RNA synthetases, in Theory and Practice in Affinity Techniques, (ed. Sundaram, P. V., Eckstdn, F.) Academic Press, Lonson 1978, p. 169... 

Meroueh SO, Mobashery S. Conformational transition in the aminoacyl t-RNA site of the bacterial ribosome both in the 133. presence and absence of an aminoglycoside antibiotic. Chem. 

As shown for streptomycin, the aminoglycosides bind at the 30 S subunit of the ribosome. The formation of the initiation complex is not inhibited. The translocation of the formylmethionine or peptidyl>t-RNA from the acceptor to the peptidyl site is disturbed. The bound t-RNA shifts the ribosome during the translocation from the decoding site to the condensing site and no more aminoacyl-t-RNA is bound. 

Synthesis using Aminoacyl t-RNA Synthetase. Other interesting synthetic reactions using ATP are the use of aminoacyl t-RNA synthetase (ARS, E.C. sub-class 6.1.1) to synthesize peptides (9-72) and for the construction of the fascinating biologically-active nucleotide, diadenosine polyphosphate (Ap4A) (13-14). ARS isolated from mesophiles is quite unstable and is usually handled on ice. ARS from B. stearothermophilus, on the other hand, is quite stable and is a useful catalyst for bioreactors. 

Peptides. It is well know that, in the first stage of aminoacyl t-RNA formation, an amino acid reacts with ATP, and aminoacyl AMP intermediate is formed. This intermediate is easily attacked by nucleophiles such as the amino group of a second amino acid or peptide (Equation 4). Table I summarizes some of the dipeptides produced using this reaction. The reac-... 

Assuming validity of the prevailing electrostatic nature for more distant aminoacid residues in enzyme catalytic activity we examined in systematic way the activity of one of the oldest enzymes on Earth i.e. aminoacyl t-RNA synthethases (aa-RS) involved in translation of DNA code into aminoacid sequence. Due to the old evolutionary age of this enzyme there is very little homology between all 20 different aminoacid variants of this enzyme, al-... 

Catalytic residues present in motif 2 and motif 3 of Class II aminoacyl t-RNA synthetases (EC - E. coli SC - S. cerevisiae HA - Hamster TT - Thermus thermopilus)... 

Figure 6.4 Formation of peptide bond via the action of aminoacyl t-RNA.

It is the aminoacyl-t-RNAs which enter the protein-synthesising system proper (ribosome-m-RNA complex). Each t-RNA species is recognised by virtue of a sequence of bases in a particular part (the coding site) of the t-RNA molecule. The sequence of bases in the coding site has been shown in some of the most intensively studied t-RNAs to be the complement (anticodon) to the m-RNA codon specifying the amino acid with which the t-RNA combines. 

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