PHENYLALANINE TRANSFER RIBONUCLEIC ACID FROM ESCHERICHIA COLI B . ISOLATION AND CHARACTERIZATION OF OLIGONUCLEOTIDES FROM RIBONUCLEASE T1 AND RIBONUCLEASE A HYDROLYSATES

Phenylalanine transfer ribonucleic acid of Escherichia coli B, exhaustively hydrolyzed by either ribonuclease T1 or ribonuclease A, yields a total of 34 oligonucleotides. These have been isolated and characterized, and account for all the bases present in the molecule, including 4-thiouracil, which is apparently in an unstable state. The oligonucleotide from each enzyme hydrolysate that contains the single 7-methylguanosine residue is routinely isolated in only 60-70% yield. E. coli B phenylalanine transfer ribonucleic acid has an unique anticodon region, A-ψ-U-G-G-A-A-A-ψ, that includes three possible anticodons in an overlapping configuration. The unexpected anticodon triplet GGA is in the most favored position stereochemically. The full potential of the remaining overlaps may be realized if the protein-synthesizing complex undergoes a conformational shift so as to utilize AAA for the UUU codon and GAA for the UUC codon. On the other hand, as in yeast phenylalanine transfer ribonucleic acid, only the GAA sequence is needed to fulfill the anticodon requirements. © 1969, American Chemical Society. All rights reserved.