Purification and Partial Characterization of the Aminoacyl Transfer Ribonucleic Acid Binding Enzyme from Rabbit Reticulocytes

The aminoacyl transfer RNA binding enzyme has been purified to apparent homogeneity from rabbit reticulocytes. The active protein is a single molecular species. It catalyzes the guanosine triphosphate-dependent binding of phenylalanyl transfer RNA to ribosomes in the presence of polyuridylic acid, has activity as a ribosome and aminoacyl transfer RNA-dependent guanosine triphosphatase, and is required for the synthesis of peptides from aminoacyl transfer RNA. The protein has a molecular weight of 186,000 and an s20,w of 6.7 S. In the presence of dissociating agents (8 m urea or 5 m guanidine-HCl) the protein undergoes dissociation into subunits of molecular weight 62,000. The results indicate that the native protein consists of three, possibly identical, subunits.