Correlation Between Crystal and Solution Structures in tRNA. Yeast tRNAPhe and tRNAAsp the Models for Free and Messenger RNA Bound tRNAs

Abstract

The three-dimensional structures of two elongator transfer RNAs are known in great details: first that of yeast tRNA(Phe) (1–4) and more recently that of yeast tRNA(Asp) (5–8). As seen in Figure 1, both molecules are folded in an L-shaped conformation, which is also found for initiator tRNAs (9,10). Since the conserved or semi-conserved residues (11) are involved in the tertiary interactions which stabilize this folding (1–10), the L-shaped structure represents the general structural organization of all tRNA molecules. Such structural similarity is satisfactory to explain common functions of tRNAs, namely the interaction with ribosomes, and in the case of elongator tRNAs with elongator factors, but not sufficient to account for specific functions. In that case specific structural features must be involved. Differences in the anticodon sequences account for the decoding of the genetic message on mRNA. Recognition by aminoacyl-tRNA synthetases, which leads to the specific ami noacylation of tRNAs is more complex. Because many aminoacyl-tRNA synthetases recognize isoacceptor tRNAs and catalyze tRNA mischarging (12), these features cannot be simple linear nucleotide sequences, but more likely structural domains found at the three-dimensional level.