EVOLUTIONARY CONSERVATION OF SYNTHETASE RECOGNITION SITE OF ALANINE TRANSFER RIBONUCLEIC ACID

The species specificity for transfer ribonucleic acidwr and aminoacyl transfer ribonucleic acid synthetase between Escherichia coli and human spleen was tested for eight amino acids. Three classes of reaction were found: (1) complete crossreactivity: alanine, arginine, lysine: (2) human spleen transfer ribonucleic acid recognized by the E. coli enzyme, but the E. coli transfer ribonucleic acid only weakly recognized by human enzyme: valine; and (3) partial or no cross-reactivity: leucine, phenylalanine, proline, serine. Alanine acylation was examined further. Human spleen, rabbit liver, and E. coli B transfer ribonucleic acid were fractionated by Freon reversed-phase chromatography, and the alanine transfer ribonucleic acid species from each organism were identified. Heterologous acylation assays indicated that each alanine transfer ribonucleic acid species could be acylated by enzyme isolated from any of the three organisms. As an evolutionary divergent source of material, lobster muscle transfer ribonucleic acid was purified. This transfer ribonucleic acid was also acylated to an equal extent by enzymes from human, rabbit, and E. coli. It appears, therefore, that there is a complete cross-reactivity of alanine transfer ribonucleic acid species with alanyl transfer ribonucleic acid synthetases. This conclusion implies that the synthetase recognition site for alanine transfer ribonucleic acid has been conserved throughout the evolutionary development of bacteria to man. © 1969, American Chemical Society. All rights reserved.