Studies on the Formation of Transfer Ribonucleic Acid-Ribosome Complexes

Phenylalanyl transfer ribonucleic acid (tRNA) bound to 70 S ribosomes in response to a template is protected from alkaline hydrolysis. Neither the 30 nor the 50 S subunit alone provides this protection. Although aminoacyl-tRNA is bound to the 30 S subunit-template complex through the anticodon, the addition of 50 S subunits is necessary for the protection from deacylation. The aminoacyl end of tRNA is thus probably intimately associated with the 50 S subunit. These results suggest that there are at least two areas on a single tRNA molecule interacting with ribosomes and the binding of tRNA to 70 S ribosomes occurs in at least two distinct steps: first, the binding of the tRNA anticodon to the 30 S-template complex; and second, the association of the aminoacyl end of the tRNA with the 50 S subunit.