Molecular mechanism of substrate recognition and specificity of tRNA^His guanylyltransferase during nucleotide addition in the 3′–5′ direction

Nucleotide addition reaction for natural NTPs and various GTP analogs onto the developed two-piece tRNA. (A) Reaction scheme of nucleotide addition reaction with natural NTPs and various GTP analogs (XTP) into 5′-triphosphorylated P4-T3. (B) Natural NTPs and GTP analogs used in the nucleotide addition reaction. (C–F) The relative k_obs values of nucleotide addition reactions with various GTP analogs for the template Y = A (C), Y = C (D), Y = U (E), and Y = G (F). Values are relative to the k_obs value of wild-type activity (GTP addition in Y = A), which was set at 1.0. The bars in the graphs are SD of more than two independent experiments.