T-RNA

Transfer or soluble RNAs are specific carrier molecules for amino-acids during protein synthesis on ribosomes with ribosomal RNA as the template. There is at least one t-RNA molecule for each amino-acid. 

The amino acid 58 was used in the solid-phase synthesis of sequence-specific DNA binding polyamides containing N-methylimidazole and N-methylpyrrole amino acids <96JACS6141> and it was also reported that the imidazole-acridine conjugate 59 could effectively catalyze the cleavage of t-RNA <96TL4417>. 

Table 8 Binding parameters of t-RNA complexation with berberine and palmatine obtained from spectrophotometric, spectrofluorimetric and isothermal titration calorimetric study [214]... 

Ligases t-RNA synthetase DNA ligase Carbonic anhydrase All phyla... 

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... 

Aminoacyl adenylates (296), which are formed from protein amino acids and ATP, act as acylating agents towards t-RNAs, acylating their terminal 3 -hydroxy groups. These charged tRNAs are then used in protein synthesis. Little is known about the reactivity of aminoacyl adenylates (296), and studies are now reported of a model compound, alanyl ethyl phosphate (297). As expected, hydrolysis in both acid and base involves attack at the C=0 group of (297) with departure of ethyl phosphate. Metal ions (Cu +, Zn +) were found to act as catalysts of the hydrolysis. 

Protein synthesis means translation into a peptide chain of a genetic message first copied (transcribed) into m-RNA (p. 274). Amino acid (AA) assembly occurs at the ribosome. Delivery of amino acids to m-RNA involves different transfer RNA molecules (t-RNA), each of which binds a specific AA. Each t-RNA bears an anticodon nucleobase triplet that is complementary to a particular m-RNA coding unit (codon, consisting of 3 nucleobases. 

The ribosome focuses two codons on m-RNA one (at the left) has bound its t-RNA-AA complex, the AA having already been added to the peptide chain the other (at the right) is ready to receive the next t-RNA-AA complex. 

After the latter attaches, the AAs of the two adjacent complexes are linked by the action of the enzyme peptide synthetase (peptidyltransferase). Concurrently, AA and t-RNA of the left complex disengage. 

The left t-RNA dissociates from m-RNA. The ribosome can advance along the m-RNA strand and focus on the next codoa... 

Consequently, the right t-RNA-AA complex shifts to the left, allowing the next complex to be bound at the right. 

The actual information transfer is based on the interaction between the mRNA codons and another type of RNA, transfer RNA (tRNA see p. 82). tRNAs, of which there are numerous types, always provide the correct amino acid to the ribosome according to the sequence information in the mRNA. tRNAs are loaded with an amino acid residue at the 3 end. Approximately in the middle, they present the triplet that is complementary to each mRNA codon, known as the anticodon (GAA in the example shown). If the codon UUC appears on the mRNA, the anticodon binds a molecule of Phe-t-RNA to the mRNA (5) and thus brings the phenylalanine residue at the other end of the molecule into a position in which it can take over the growing polypeptide chain from the neighboring tRNA (6). 

DTT-dependent and -independent RNAse inhibitors (Ambion), NTPs, dNTPs, MgClj, MnCl, yeast t-RNA, DNA, and RNA molecular weight standards. 

For the recovery and purification of the eluted RNA, add 5 pg t-RNA as a carrier, and phenol- and chloroform-extract the eluate, precipitate with ethanol, and resuspend the pellet in 12 pi DEPC-treated HjO-... 

Determination of unspecific binding reaction by competition of the RNA aptamers with cocaine 79 pi incubation buffer, 10 pi nAChR-enriched plasma membranes (800 pg/ml protein 1.6 pM receptor), 1 pi P-RNA dilution containing 10 mg/ml t-RNA anti-RNAse (40 U/pl), and 10 pi cocaine (10 mM). The percentage of binding of the ( P) RNA aptamers to the... 

Not only proteins and their oligomers, but nucleic acids as well give beautiful examples of self-organization - think of the formation of the DNA duplex, where the primary structure of the two strands determines the rules for self-assembly or the folding of t-RNA. 

Figure 5.8 Folding of t-RNA, another classic case of self-organization.

The RNA was then added to the vesicle solution in separate experiments. The size distribution of the vesicles before and after the addition of t-RNA was investigated by dynamic light scattering and by direct ultraviolet (UV) optical density observation. 

Several questions can be posed at this level. For example can simple matrices be developed that are operative in vitro as ribosomes Can one operate, at costs of specificity, with only a very few polymerases Similarly, reasoning that it might not be necessary for the very beginning to have all specific t-RNAs, can a few unspecific ones be used instead Also, experiments with a limited number of amino acids might even be conceived. 

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