Studies on the Formation of Transfer Ribonucleic Acid-Ribosome Complexes

Aminoacyl-oligonucleotides representing the terminal fragments of aminoacyl-tRNA were synthesized and characterized: C-A-C-C-A(Phe), C-C-A(Phe), C-C-A(Leu), C-C-A-(Lys), C-C-A(Ser), C-C-A(Glu) and C-C-A(Ala). Since these fragments represent the aminoacyl-end of aminoacyltRNA, it was not surprising to find that puromycin inhibits their binding. In addition, their binding to ribosomes was stimulated by ethanol. Their affinity to ribosomes was in the order C-C-A(Phe) g C-C-A(Leu) g C-C-A(Lys) g C-C-A(Ser) g C-C-A(Ala) g C-C-A(Glu). Since their oligonucleotide portions are identical, it is evident that differences in their binding to ribosomes reflect differences in interaction of their amino acid residues with ribosomes and may have physiological significance. These aminoacyloligonucleotides are able to serve as acceptors for the transfer of peptide from peptidyl-tRNA. However, they are poor and ineffective as donors in the puromycin reaction. In addition, in the presence of ethanol these compounds readily undergo ethanolysis to form the respective aminoacyl ethyl esters. Furthermore, washing of ribosomes with 1 m NH4Cl and 0.01 m MgCl2 is not sufficient to remove completely peptidyl-tRNA from ribosomes.