Species Specificity of Amino Acid Acceptor Ribonucleic Acid and Aminoacyl Soluble Ribonucleic Acid Synthetases.

Several investigators have reported that the activation of amino acids for protein synthesis, i.e. the incorporation of amino acids into soluble ribonucleic acids, is dependent upon the source of both the aminoacyl S-RNA’ synthetases and the S-RNA itself. For example, Rendi and Ochoa (1) reported that aminoacyl S-RNA synthetases from Escherichia coli could not incorporate leucine into yeast or rat liver S-RNA, and vice versa. Benzer and Weisblum (2) compared the specificities of S-RNA and aminoacyl S-RNA synthetases in E. co& yeast, and rabbit liver. They found striking differences; however, the pattern depended upon the particular amino acid in question. Clark and Eyzaguirre (3) and Berg et al. (4) demonstrated species specificities in the cases of tyrosine and methionine incorporation, respectively. The species differences observed in these investigations suggest that amino acid incorporation is dependent not only upon the aminoacyl S-RNA synthetases and S-RNA, but also upon the amino acid in question. Although the species differences observed in many instances are quite striking, it is possible that certain homologies may exist (2). The purpose of this investigation is to show the existence of such homologies and further investigate the species differences that exist in cases heretofore uninvestigated. The observations presented here further show that the amino acid acceptor activity of at least one RNA is altered by the presence of a small amount of spermine. The principles of laboratory animal care as promulgated by the National Society for Medical Research were observed.