Covalent joining of phenylalanine transfer ribonucleic acid half-molecules by T4 RNA ligase.

RNA ligase from T4-phage-infected Escherichia coli cells catalyzes the covalent joining of two polynucleotides that are partially hydrogen-bonded to each other. Two polynucleotide fragments derived from yeast tRNA(Phe) and consisting of residues 1-36 and 38-74 are covalently joined by the enzyme. The product of the reaction lacks residue Y(37) and has an anticodon loop with six nucleotide residues, whereas all tRNA species whose sequences have so far been determined have seven nucleotides in this loop. Evidence is also presented for the formation of a polynucleotide-adenylylate intermediate in the joining reaction, in which a pyrophosphate bond links the 5'-phosphoryl terminus of the polynucleotide and the phosphoryl group of AMP.