Interaction of Eukaryote Elongation Factor EF 1 with Guanosine Nucleotides and Aminoacyl-tRNA

Evidence for two species of elongation factor 1 (EF 1Aand EF 1B) from calf brain has been obtained by molecular sieve chromatography on Sephadex G-150. A high molecular weight form, EF 1A, interacts with GTP to form an EF 1A-GTP complex. GDP also reacts with EF 1, but unlike the reaction with GTP, an EF 1B-GDP complex is formed that contains a lower molecular weight and labile species of EF 1. The results also indicate that EF 1A-GTP reacts with aminoacyl-tRNA to form an aminoacyl-tRNA-EF 1B-GTP complex. These results are discussed with regard to the role of EF 1 in aminoacyl-tRNA binding to ribosomes.