Structure and Function of Transfer Ribonucleic Acid

The formation of a stable complex between valyl transfer ribonucleic acid synthetase from yeast and transfer RNA specific for valine (tRNAval) from the same source has been used as a model for the recognition between enzyme and tRNA. With the use of sucrose gradient centrifugation to isolate the complex, the major fraction of tRNAval (tRNA1val) was found to retain its ability to form a stable complex with the enzyme even after a digestion with snake venom phosphodiesterase that had removed as much as an average of 7 nucleotide residues from the 3'-hydroxyl end. The digested tRNAs also showed competitive inhibition of complex formation with native tRNA1val and the relative affinities of the enzyme for the different tRNA1val preparations that could be calculated from the inhibition experiments showed that this extensive modification at the 3'-hydroxyl end had not lowered the affinity of the enzyme for the modified tRNA1val compared to native tRNA1val by more than a factor of 2.