Transfer RNA and Its Aminoacylation A. Primary and Secondary Structures of tRNA 1. All organisms contain many species of tRNAs which are not easily separated 2. A 5-bp stem ending in a loop that contains the anticodon e. Only 42 of its 76 bases occur in the double helical stems b. 71 of them participate in stacking associations 3. The compact structure of tRNA results from its large number of intramolecular associations, which renders most of its bases inaccessible to solvent C. Aminoacyl-tRNA Synthetases 1.
Accurate translation requires two equally important recognition steps a.
The selection of the amino acid-charged tRNA specified by mRNA 2. Accurate translation therefore requires not only that each tRNA be aminoacylated by its cognate aaRS but that it not be aminoacylated by any of its 19 noncognate aaRSs 4. The available experimental evidence has largely located the various tRNA identifiers in the acceptor stem and the anticodon loop 6. The enzyme's overall selectivity is therefore the product of the selectivities of its adenylation and proofreading steps, thereby accounting for the high fidelity of translation 8. Editing occurs at the expense of ATP hydrolysis D. Codon-Anticodon Interactions 1.