The Role of the Adenosine Terminus of Transfer Ribonucleic Acid in the Specific Binding to Ribosomes and Their Subunits

Abstract

Abstract The binding of 14C-phenylalanyl-tRNA to 70 S ribosomes was inhibited by the addition of the following tRNA preparations: 1, tRNA preparation in which no tRNA was acylated (tRNAmixCpCpA); 2, tRNA preparation in which all tRNA except for the one specific for phenylalanine have lost their terminal adenosine (tRNAmix-pheCpCp and tRNApheCpCpA); 3), tRNA preparation in which all the tRNA have lost their terminal adenosine (tRNAmixCpCp); and 4, tRNA preparation in which all tRNA have lost their terminal adenylic acid (tRNAmixCpC). The efficiency of inhibition was in the order of: 1 g 2 g 3 = 4. The binding of 14C-phenylalanyl-tRNA to the 30 S ribosomal subunits was inhibited by the various tRNA preparations listed above (1, 3, and 4) but there was no difference in the inhibitory efficiencies between these preparations of tRNA. Preparation 2 (tRNAmix-pheCpCp and tRNApheCpCpA) was more efficiently utilized than tRNA Preparation 1 (tRNAmixCpCpA) for polyphenylalanine formation. The 14C-phenylalanyl-tRNA prepared from 2 had a higher rate of binding to the complex of 70 S ribosomes and polyuridylic acid than 14C-phenylalanyl-tRNA prepared from 1. These results indicate that for binding of tRNA to 30 S ribosomal subunits the terminal adenosine of tRNA is not important while binding to 70 S subunits involves both the anticodon region and the terminal adenosine of tRNA. In the latter process, the presence of tRNA other than the specific tRNA coded by the corresponding messenger RNA has an inhibitory effect.