Transfer of methionyl residues by leucyl,phenylalanyl-tRNA-protein transferase

Leucyl, phenylalanyl-tRNA-protein transferase also catalyzes transfer of methionyl residues as indicated by (i) copurification over a 1000-fold range of transfer activities for all three amino acids and (ii) loss of methionyl transfer activity in a mutant of $\text{E.}\text{coli}$ lacking the transferase and reappearance of this activity in a transferase revertant. The purified enzyme was found to use Met-tRNA_m^Met in preference to Met-tRNA_f^Met as donor substrate. Peptides containing a basic amino acid at the NH₂-terminus functioned as acceptors for the transfer of methionyl residues.