COMPOSITION OF ACTIVE INTERMEDIATE IN TRANSFER OF AMINOACYL-RNA TO RIBOSOMES

It was first shown in this laboratory (1,2) that one of the fractions obtained from extracts of Escherichia coli W by chromatography on DEAE-Sephadex catalyzes the GTP-dependent binding of aminoacyl-RNA to E. coli ribosomes in a manner analogous to that previously reported for the rabbit reticulocyte system (3,4). Further investigation (5,6) indicated that this fraction interacts with GTP in the presence of aminoacyl-RNA to form a complex which serves as the active intermediate in the enzymatic transfer of aminoacyl-RNA to E. coli ribosomes. Similar findings have also been reported by other investigators (7-12). Evidence has been obtained recently (13,14) that two protein fractions, differing in heat lability, are required for the formation of a GTP-protein complex and for the GTP-dependent transfer of aminoacyl-RNA to ribosomes. In the present investigation, evidence is presented which demonstrates that the active intermediate for the transfer of aminoacyl-RNA to ribosomes is a complex composed of aminoacyl-RNA, GTP, and the heat labile transfer factor. © 1968.