Properties of the 5'-terminus of tRNAHis: kinetics of polynucleotide kinase catalyzed exchange and effect of dephosphorylation on the aminoacylation reaction.

Bacteriophage T₄ induced polynucleotide kinase was found to be ineffective in transferring ³²P from [γ-³²P]ATP to the 5′-terminus of 5′-phosphorylated $\text{E. coli}$ tRNA^His using the ADP mediated exchange reaction. However, prior dephosphorylation with alkaline phosphatase allowed polynucleotide kinase catalyzed phosphorylation of tRNA^His. Contrary to reports for other tRNA species, alkaline phosphatase catalyzed 5′-terminus dephosphorylation destroys the amino acid accepting ability of tRNA^His. Aminoacylation competency of the tRNA^His is restored after phosphorylation with polynucleotide kinase.