ULTRAVIOLET INACTIVATION OF FUNCTIONS OF PHENYLALANINE AND LYSINE TRANSFER RNAS OF ESCHERICHIA COLI

Ultraviolet inactivation of phenylalanine and lysine transfer RNA's (tRNAPhe and tRNALys) of Escherichia coli was studied with respect to amino acid acceptance, amino acid transfer to ribosomes, and specific binding to 70-S ribosomes and 30-S ribosomal subunits. It was found that the cross sections of the specific binding to 70-S ribosomes and to 30-S subunits were identical to each other for both tRNAPhe and tRNALys. The cross section of the amino acid transfer to ribosomes was also almost identical to that of the specific binding for both of the tRNA's. In the case of tRNAPhe, the cross section of amino acid transfer to ribosomes from tRNA irradiated in the deacylated state was nearly equal to the sum of the cross section of the aminoacylation and that of the transfer from the tRNA irradiated in the aminoacylated state, indicating nonoverlapping of the functional sites responsible for amino acid acceptance and transfer. On the other hand, a substantial overlap of the critical sites for the two functions was indicated for tRNALys. When the tRNA's were irradiated in the solution with Mg2+, the inactivation cross sections decreased compared to those obtained by irradiation in the solution without Mg2+ and with low salt content, but the above interrelationship between the cross sections remained essentially the same for both sets of irradiation conditions. © 1969.